Merge branch 'dev' into edge

2016-10-12 19:18:34 -06:00 · 2016-10-12 19:18:34 -06:00 · 62d16af285
commit 62d16af285
parent 0746a5a1d7 a0e96eb11a
52 changed files with 5659 additions and 2477 deletions
--- a/2
+++ b/2
@ -4,7 +4,7 @@ COPYRIGHT NOTICE FOR GRBL:
 Grbl - Embedded CNC g-code interpreter and motion-controller
-Copyright (c) 2011-2015 Sungeun K. Jeon
+Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
 Copyright (c) 2009-2011 Simen Svale Skogsrud
 Copyright (c) 2011 Jens Geisler
--- a/12
+++ b/12
@ -1,7 +1,7 @@
 #  Part of Grbl
 #
 #  Copyright (c) 2009-2011 Simen Svale Skogsrud
-#  Copyright (c) 2012-2015 Sungeun K. Jeon
+#  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
 #
 #  Grbl is free software: you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@ -32,7 +32,7 @@ DEVICE     ?= atmega328p
 CLOCK      = 16000000
 PROGRAMMER ?= -c avrisp2 -P usb
 SOURCE    = main.c motion_control.c gcode.c spindle_control.c coolant_control.c serial.c \
-             protocol.c stepper.c eeprom.c settings.c planner.c nuts_bolts.c limits.c \
+             protocol.c stepper.c eeprom.c settings.c planner.c nuts_bolts.c limits.c jog.c\
             print.c probe.c report.c system.c
 BUILDDIR = build
 SOURCEDIR = grbl
@ -42,7 +42,13 @@ FUSES      = -U hfuse:w:0xd2:m -U lfuse:w:0xff:m
 # Tune the lines below only if you know what you are doing:
 AVRDUDE = avrdude $(PROGRAMMER) -p $(DEVICE) -B 10 -F
-COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections -fdata-sections
+
 # Compile flags for avr-gcc v4.8.1. Does not produce -flto warnings.
 COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections
 # Compile flags for avr-gcc v4.9.2 compatible with the IDE. Or if you don't care about the warnings. 
 # COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections -flto
 OBJECTS = $(addprefix $(BUILDDIR)/,$(notdir $(SOURCE:.c=.o)))
--- a/README.md
+++ b/README.md
@ -3,25 +3,25 @@
 ***
-_**This is the development branch for Grbl v1.0's upcoming release. In general, the new features here are beta, so use with caution. If you'd like to help, please report any bugs or oddities that you find! Thanks!**_
+_**This is the development branch for Grbl v1.1's upcoming release. Please keep in mind, the new features here are beta, so use with caution. If you'd like to help, please report any bugs or oddities that you find! Thanks!**_
 ***
-Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. It will run on a vanilla Arduino (Duemillanove/Uno) as long as it sports an Atmega 328. 
+Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. This version of Grbl runs on an Arduino Uno.
 The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain up to 30kHz of stable, jitter free control pulses.
 It accepts standards-compliant g-code and has been tested with the output of several CAM tools with no problems. Arcs, circles and helical motion are fully supported, as well as, all other primary g-code commands. Macro functions, variables, and most canned cycles are not supported, but we think GUIs can do a much better job at translating them into straight g-code anyhow.
-Grbl includes full acceleration management with look ahead. That means the controller will look up to 18 motions into the future and plan its velocities ahead to deliver smooth acceleration and jerk-free cornering.
+Grbl includes full acceleration management with look ahead. That means the controller will look up to 16 motions into the future and plan its velocities ahead to deliver smooth acceleration and jerk-free cornering.
-* [Licensing](https://github.com/grbl/grbl/wiki/Licensing): Grbl is free software, released under the GPLv3 license.
+* [Licensing](https://github.com/gnea/grbl/wiki/Licensing): Grbl is free software, released under the GPLv3 license.
-* For more information and help, check out our **[Wiki pages!](https://github.com/grbl/grbl/wiki)** If you find that the information is out-dated, please to help us keep it updated by editing it or notifying our community! Thanks!
+* For more information and help, check out our **[Wiki pages!](https://github.com/gnea/grbl/wiki)** If you find that the information is out-dated, please to help us keep it updated by editing it or notifying our community! Thanks!
-* Lead Developer [_2011 - Current_]: Sungeun(Sonny) K. Jeon, Ph.D. (USA) aka @chamnit
+* Lead Developer: Sungeun "Sonny" Jeon, Ph.D. (USA) aka @chamnit
-* Lead Developer [_2009 - 2011_]: Simen Svale Skogsrud (Norway). aka The Originator/Creator/Pioneer/Father of Grbl.
+* Built on the wonderful Grbl v0.6 (2011) firmware written by Simen Svale Skogsrud (Norway).
 ***
@ -31,26 +31,41 @@ Grbl includes full acceleration management with look ahead. That means the contr
 ***
-##Update Summary for v1.0c
+##Update Summary for v1.1
 - **IMPORTANT:** Your EEPROM will be wiped and restored with new settings. This is due to the addition of two new spindle speed '$' settings.
- Altered limit pin status reports from `Lim:000` to `Pin:000|0|0000`, where the `|` delimiters separate the new probe state and control pin states. Each new field may be disabled by the `$10` Grbl setting. NOTE: Commenting `REPORT_ALL_PIN_STATES` in config.h reverts to old `Lim:` reports, if needed.
+- **Real-time Overrides** : Alters the machine running state immediately with feed, rapid, spindle speed, spindle stop, and coolant toggle controls. This awesome new feature is common only on industrial machines, often used to optimize speeds and feeds while a job is running. Most hobby CNC's try to mimic this behavior, but usually have large amounts of lag. Grbl executes overrides in realtime and within tens of milliseconds.
- New safety door parking motion as a compile-option. Grbl will retract, disable the spindle/coolant, and park near Z max. When resumed, it will perform these task in reverse order and continue the program. Highly configurable. See config.h for details.
+- **Jogging Mode** : The new jogging commands are independent of the g-code parser, so that the parser state doesn't get altered and cause a potential crash if not restored properly. Documentation is included on how this works and how it can be used to control your machine via a joystick or rotary dial with a low-latency, satisfying response.
 - **Laser Mode** : The new "laser" mode will cause Grbl to move continuously through consecutive G1, G2, and G3 commands with spindle speed changes. When "laser" mode is disabled, Grbl will instead come to a stop to ensure a spindle comes up to speed properly. Spindle speed overrides also work with laser mode so you can tweak the laser power, if you need to during the job. Switch between "laser" mode and "normal" mode via a `$` setting.
 - **Sleep Mode** : Grbl may now be put to "sleep" via a `$SLP` command. This will disable everything, including the stepper drivers. Nice to have when you are leaving your machine unattended and want to power down everything automatically. Only a reset exits the sleep state.
 - **Significant Interface Improvements**: Just this one time and done simultaneously with adding override data and controls, Grbl has tweaked the communication interface to make it easier for developers to write and maintain their GUIs. _NOTE: GUIs need to specifically update their code to be compatible with v1.1 and later._
 	- **New Status Reports**: To account for the additional override data, status reports have been tweaked to cram more data into it, while still being smaller than before. Documentation is included, outlining how it has been changed. 
 	- **Improved Error/Alarm Feedback** : All Grbl error and alarm messages have been changed to providing a code. Each code is associated with a specific problem, so users will know exactly what is wrong without having to guess. Documentation and an easy to parse CSV is included in the repo.
 	- **Extended-ASCII realtime commands** : All overrides and future real-time commands are defined in the extended-ASCII character space. Unfortunately not easily type-able on a keyboard, but helps prevent accidental commands from a g-code file having these characters and gives lots of space for future expansion.
 	- **Message Prefixes** : Every message type from Grbl has a unique prefix to help GUIs immediately determine what the message is and parse it accordingly without having to know context. The prior interface had several instances of GUIs having to figure out the meaning of a message, which made everything more complicated than it needed to be.
 - New OEM specific features, such as safety door parking, single configuration file build option, EEPROM restrictions and restoring controls, and storing product data information.
 - New safety door parking motion as a compile-option. Grbl will retract, disable the spindle/coolant, and park near Z max. When resumed, it will perform these task in reverse order and continue the program. Highly configurable, even to add more than one parking motion. See config.h for details.
 - New '$' Grbl settings for max and min spindle rpm. Allows for tweaking the PWM output to more closely match true spindle rpm. When max rpm is set to zero or less than min rpm, the PWM pin D11 will act like a simple enable on/off output.
 - Updated G28 and G30 behavior from NIST to LinuxCNC g-code description. In short, if a intermediate motion is specified, only the axes specified will move to the stored coordinates, not all axes as before.
- **NOTE:** Arduino Mega2560 support has been moved to an active, official Grbl-Mega [project](http://www.github.com/gnea/grbl-Mega/). All new developments here and there will be synced when it makes sense to.
+- Lots of minor bug fixes and refactoring to make the code more efficient and flexible.
- A few bug fixes and lots of refactoring to make the code more efficient and flexible.
+- **NOTE:** Arduino Mega2560 support has been moved to an active, official Grbl-Mega [project](http://www.github.com/gnea/grbl-Mega/). All new developments here and there will be synced when it makes sense to.
 -
 ```
-List of Supported G-Codes in Grbl v0.9 Master:
+List of Supported G-Codes in Grbl v1.1:
  - Non-Modal Commands: G4, G10L2, G10L20, G28, G30, G28.1, G30.1, G53, G92, G92.1
  - Motion Modes: G0, G1, G2, G3, G38.2, G38.3, G38.4, G38.5, G80
  - Feed Rate Modes: G93, G94
--- a/doc/csv/alarm_codes_en_US.csv
+++ b/doc/csv/alarm_codes_en_US.csv
@ -0,0 +1,10 @@
 (KEY: Alarm Code in v1.1+, Alarm Message in v1.0-, Alarm Description)
 1,Hard limit,Hard limit has been triggered. Machine position is likely lost due to sudden halt. Re-homing is highly recommended.
 2,Soft limit,Soft limit alarm. G-code motion target exceeds machine travel. Machine position retained. Alarm may be safely unlocked.
 3,Abort during cycle,Reset while in motion. Machine position is likely lost due to sudden halt. Re-homing is highly recommended.
 4,Probe fail,Probe fail. Probe is not in the expected initial state before starting probe cycle when G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered.
 5,Probe fail,Probe fail. Probe did not contact the workpiece within the programmed travel for G38.2 and G38.4.
 6,Homing fail,Homing fail. The active homing cycle was reset.
 7,Homing fail,Homing fail. Safety door was opened during homing cycle.
 8,Homing fail,Homing fail. Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring.
 9,Homing fail,Homing fail. Could not find limit switch within search distances. Try increasing max travel, decreasing pull-off distance, or check wiring.
--- a/doc/csv/error_codes_en_US.csv
+++ b/doc/csv/error_codes_en_US.csv
@ -0,0 +1,35 @@
 (KEY: Error Code in v1.1+ ,Error Message in v1.0-, Error Description)
 1,Expected command letter,G-code words consist of a letter and a value. Letter was not found.
 2,Bad number format,Missing the expected G-code word value or numeric value format is not valid.
 3,Invalid statement,Grbl '$' system command was not recognized or supported.
 4,Value < 0,Negative value received for an expected positive value.
 5,Setting disabled,Homing cycle failure. Homing is not enabled via settings.
 6,Value < 3 usec,Minimum step pulse time must be greater than 3usec.
 7,EEPROM read fail. Using defaults,An EEPROM read failed. Auto-restoring affected EEPROM to default values.
 8,Not idle,Grbl '$' command cannot be used unless Grbl is IDLE. Ensures smooth operation during a job.
 9,G-code lock,G-code commands are locked out during alarm or jog state.
 10,Homing not enabled,Soft limits cannot be enabled without homing also enabled.
 11,Line overflow,Max characters per line exceeded. Received command line was not executed.
 12,Step rate > 30kHz,Grbl '$' setting value cause the step rate to exceed the maximum supported.
 13,Check Door,Safety door detected as opened and door state initiated.
 14,Line length exceeded,Build info or startup line exceeded EEPROM line length limit. Line not stored.
 15,Travel exceeded,Jog target exceeds machine travel. Jog command has been ignored.
 16,Invalid jog command,Jog command has no '=' or contains prohibited g-code.
 20,Unsupported command,Unsupported or invalid g-code command found in block.
 21,Modal group violation,More than one g-code command from same modal group found in block.
 22,Undefined feed rate,Feed rate has not yet been set or is undefined.
 23,Invalid gcode ID:23,G-code command in block requires an integer value.
 24,Invalid gcode ID:24,More than one g-code command that requires axis words found in block.
 25,Invalid gcode ID:25,Repeated g-code word found in block.
 26,Invalid gcode ID:26,No axis words found in block for g-code command or current modal state which requires them.
 27,Invalid gcode ID:27,Line number value is invalid.
 28,Invalid gcode ID:28,G-code command is missing a required value word.
 29,Invalid gcode ID:29,G59.x work coordinate systems are not supported.
 30,Invalid gcode ID:30,G53 only allowed with G0 and G1 motion modes.
 31,Invalid gcode ID:31,Axis words found in block when no command or current modal state uses them.
 32,Invalid gcode ID:32,G2 and G3 arcs require at least one in-plane axis word.
 33,Invalid gcode ID:33,Motion command target is invalid.
 34,Invalid gcode ID:34,Arc radius value is invalid.
 35,Invalid gcode ID:35,G2 and G3 arcs require at least one in-plane offset word.
 36,Invalid gcode ID:36,Unused value words found in block.
 37,Invalid gcode ID:37,G43.1 dynamic tool length offset is not assigned to configured tool length axis.
--- a/doc/csv/setting_codes_en_US.csv
+++ b/doc/csv/setting_codes_en_US.csv
@ -0,0 +1,35 @@
 (KEY: $-Code, Setting, Units, Setting Description)
 0,Step pulse time,microseconds,Sets time length per step. Minimum 3usec.
 1,Step idle delay,milliseconds,Sets a short hold delay when stopping to let dynamics settle before disabling steppers. Value 255 keeps motors enabled with no delay.
 2,Step pulse invert,mask,Inverts the step signal. Set axis bit to invert (00000ZYX).
 3,Step direction invert,mask,Inverts the direction signal. Set axis bit to invert (00000ZYX).
 4,Invert step enable pin,boolean,Inverts the stepper driver enable pin signal.
 5,Invert limit pins,boolean,Inverts the all of the limit input pins.
 6,Invert probe pin,boolean,Inverts the probe input pin signal.
 10,Status report options,mask,Alters data included in status reports.
 11,Junction deviation,millimeters,Sets how fast Grbl travels through consecutive motions. Lower value slows it down.
 12,Arc tolerance,millimeters,Sets the G2 and G3 arc tracing accuracy based on radial error. Beware: A very small value may effect performance.
 13,Report in inches,boolean,Enables inch units when returning any position and rate value that is not a settings value.
 20,Soft limits enable,boolean,Enables soft limits checks within machine travel and sets alarm when exceeded. Requires homing.
 21,Hard limits enable,boolean,Enables hard limits. Immediately halts motion and throws an alarm when switch is triggered.
 22,Homing cycle enable,boolean,Enables homing cycle. Requires limit switches on all axes.
 23,Homing direction invert,mask,Homing searches for a switch in the positive direction. Set axis bit (00000ZYX) to search in negative direction.
 24,Homing locate feed rate,mm/min,Feed rate to slowly engage limit switch to determine its location accurately.
 25,Homing search seek rate,mm/min,Seek rate to quickly find the limit switch before the slower locating phase.
 26,Homing switch debounce delay,milliseconds,Sets a short delay between phases of homing cycle to let a switch debounce.
 27,Homing switch pull-off distance,millimeters,Retract distance after triggering switch to disengage it. Homing will fail if switch isn't cleared.
 30,Maximum spindle speed,RPM,Maximum spindle speed. Sets PWM to 100% duty cycle.
 31,Minimum spindle speed,RPM,Minimum spindle speed. Sets PWM to 0.4% or lowest duty cycle.
 32,Laser-mode enable,boolean,Enables laser mode. Consecutive G1/2/3 commands will not halt when spindle speed is changed.
 100,X-axis travel resolution,step/mm,X-axis travel resolution in steps per millimeter.
 101,Y-axis travel resolution,step/mm,Y-axis travel resolution in steps per millimeter.
 102,Z-axis travel resolution,step/mm,Z-axis travel resolution in steps per millimeter.
 110,X-axis maximum rate,mm/min,X-axis maximum rate. Used as G0 rapid rate.
 111,Y-axis maximum rate,mm/min,Y-axis maximum rate. Used as G0 rapid rate.
 112,Z-axis maximum rate,mm/min,Z-axis maximum rate. Used as G0 rapid rate.
 120,X-axis acceleration,mm/sec^2,X-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
 121,Y-axis acceleration,mm/sec^2,Y-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
 122,Z-axis acceleration,mm/sec^2,Z-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
 130,X-axis maximum travel,millimeters,Maximum X-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.
 131,Y-axis maximum travel,millimeters,Maximum Y-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.
 132,Z-axis maximum travel,millimeters,Maximum Z-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.
--- a/doc/log/commit_log_v1.1.txt
+++ b/doc/log/commit_log_v1.1.txt
@ -0,0 +1,408 @@
 ----------------
 Date: 2016-10-12
 Author: Sonny Jeon
 Subject: Spindle speed bug fix.
 - Spindle speed updating wasn’t working in the g-code parser due to
 some borked up logic on my part. Fixed it and should be operating as
 intended for both normal and laser spindle modes.
 - Elaborated a little more on the new sleep mode in the documentation.
 ----------------
 Date: 2016-10-11
 Author: Sonny Jeon
 Subject: v1.1c: New sleep mode. Laser mode and other bug fixes.
 - New $SLP sleep mode that will disable spindle, coolant, and stepper
 enable pins. Allows users to disable their steppers without having to
 alter their settings. A reset is required to exit and re-initializes in
 alarm state.
 - Laser mode wasn’t updating the spindle PWM correctly (effected
 spindle speed overrides) and not checking for modal states either.
 Fixed both issues.
 - While in laser mode, parking motions are ignored, since the power off
 delay with the retract motion would burn the material. It will just
 turn off and not move. A restore immediately powers up and resumes. No
 delays.
 - Changing rpm max and min settings did not update the spindle PWM
 calculations. Now fixed.
 - Increased default planner buffer from 16 to 17 block. It seems to be
 stable, but need to monitor this carefully.
 - Removed software debounce routine for limit pins. Obsolete.
 - Fixed a couple parking motion bugs. One related to restoring
 incorrectly and the other the parking rate wasn’t compatible with the
 planner structs.
 - Fixed a bug caused by refactoring the critical alarms in a recent
 push. Soft limits weren’t invoking a critical alarm.
 - Updated the documentation with the new sleep feature and added some
 more details to the change summary.
 ----------------
 Date: 2016-09-28
 Author: Sonny Jeon
 Subject: New jog cancel real-time command. Parser typo fix from last push.
 - Added a new jog cancel real-time command. Rather than depending on a
 feed hold to cancel a jogging motion, this realtime command can be used
 instead. The main advantage is if a feed hold is used, you can
 accidentally hold the machine right when Grbl returns to IDLE after
 completing a jog. And the GUI doesn’t have to worry about tracking this
 either.
 - Fixed a typo in the g-code parser edits from the last push. Was
 causing the G10 set coordinate system command to not work correctly.
 - Updated the documentation with the jog cancel command.
 ----------------
 Date: 2016-09-27
 Author: Sonny Jeon
 Subject: Refactored g-code parser. Saved 60bytes flash and some ram. Edited Readme.
 - Freed up another 60 bytes of flash and 12-24 bytes of stack RAM by
 using the pre-allocated IJK arc offset vector that is guaranteed to be
 not in use. Only G10 and G28/30 require fetching from EEPROM and
 retaining extra data. Both commands use axis words, which rules out
 G2/3 arcs using IJK offsets existing in same block. Not ideal, but
 every byte helps.
 - Edited README.
 ----------------
 Date: 2016-09-27
 Author: Sonny Jeon
 Subject: Update README and clarifications in jogging document.
 ----------------
 Date: 2016-09-26
 Author: Sonny Jeon
 Subject: v1.1b: Tweaked Bf reports, jogging doc, saved another 160 bytes, minor bug fixes
 - Increment to v1.1b due to status report tweak.
 - Tweaked the buffer state status reports to show bytes and blocks
 available, rather than in use. This does not require knowing the buffer
 sizes beforehand. It’s implicit.
 - Also, since buffer states are not used by most devs (after
 inquiries), it is no longer enabled by default and a status mask option
 was added for this.
 - Fixed some typos and updated for the report tweak in the
 documentation.
 - Wrote a joystick implementation concept in the jogging markdown
 document. Outlines how to get a low-latency feel to a joystick (and
 other input devices).
 - Removed XON/XOFF support. It’s not used by anyone because of its
 inherent problems. Remains in older versions for reference.
 - Added a compile option on how to handle the probe position during a
 check mode.
 - Fixed a jogging bug. If G93 is the modal state before a jogging
 motion, the feed rate did not get calculated correctly. Fixed the issue.
 - Refactored some code to save another 160+ bytes. Included an improved
 float vector comparison macro and reducing a few large and repetitive
 function calls.
 - Fixed a probing bug (existing in v0.9 too) where the target positions
 were not set correct and error handling was improper.
 ----------------
 Date: 2016-09-25
 Author: Sonny Jeon
 Subject: Addressed much larger flash size with avr-gcc v4.9.2. Refactored reports to save 160KB.
 - The newest Arduino IDE 1.6.12 has recently updated to avr-gcc v4.9.2.
 Unfortunately, it produces a compiled size almost 0.7KB to 1KB larger
 than prior versions! This can easily cause the base build to exceed the
 Arduino Duemilanove/Nano flash limit of 30.5KB. The Arduino Uno seems
 to be ok still with its 31.5KB flash limit.
 - Makefile `-flto` compile flag added to cut down on the horrible flash
 size when using the new avr-gcc. (Edit Makefile and remove comment on
 COMPILE definition). This brings it in-line with what the IDE produces.
 - Functionalized repetitive tasks in report.c to try to reduce overall
 flash size. Successfully cut down about 160bytes.
 - Removed printFloat_SettingValue() and printFloat_RPMValue()
 functions. These aren’t required and can be replaced with a direct call
 to printFloat() because they don’t require a unit conversion check.
 ----------------
 Date: 2016-09-24
 Author: Sonny Jeon
 Subject: Serial RX count bug fix. Settings codes CSV. More documentation.
 - Reverted back the serial RX count function to how it was. The
 variable type was unsigned and cause an integer underflow whenever the
 calculation produced a negative number. The old way was the correct way.
 - Lots of minor edits to the code CSVs and markdown documents.
 - Expanded on explaining feedback messages and startup line execution
 feedback.
 - Created a new settings codes CSV to help GUIs import the values and
 meanings.
 ----------------
 Date: 2016-09-22
 Author: Sonny Jeon
 Subject: Increment to v1.1a, minor compile bug fix, tweaked communication protocol, more docs.
 - Incremented to v1.1a, rather than keep 1.0e. This is because there
 are existing v1.0 installations. Don’t want to confuse people further.
 - Certain version of the Arduino IDE did not like the `inline` in the
 function header. Removed from spindle_control files to fix the problem.
 - Tweaked the communication protocol slightly. Added message type
 indicators for all `[]`bracketed feedback messages. It’s been
 problematic for GUI dev to try to determine the context of a message
 and how it should be handled. These indictors should help tremendously
 to remove context all together.
 - Also altered how `$N` startup lines are presented when executed. They
 now start with an open chevron ‘>’ followed by the line and an ‘:ok’ to
 indicate it executed. The ‘ok’ is on the same line intentionally so it
 doesn’t mess up a streaming protocol counter.
 - Managed to save a 100+KB from refactoring parts of report.c. (Thanks
 Vasilis!) Freed up room to alter the protocol a little.
 - Wrote a markdown document on interface messaging to make it clear how
 it’s intended to work. See interface.md in /doc/markdown
 - Started to pull in some Wiki pages from the old grbl site and
 beginning to update them for v1.1.
 - Created new commit log for v1.1.
 ----------------
 Date: 2016-09-22
 Author: Sonny Jeon
 Subject: Merge pull request #1 from winder/dev
 Add locale to code CSVs.
 ----------------
 Date: 2016-09-22
 Author: winder
 Subject: Add locale to code CSVs.
 ----------------
 Date: 2016-09-21
 Author: chamnit
 Subject: Grbl v1.0e huge beta release. Overrides and new reporting.
 - Feature: Realtime feed, rapid, and spindle speed overrides. These
 alter the running machine state within tens of milliseconds!
    - Feed override: 100%, +/-10%, +/-1% commands with values 1-200% of
 programmed feed
    - Rapid override: 100%, 50%, 25% rapid rate commands
    - Spindle speed override: 100%, +/-10%, +/-1% commands with values
 50-200% of programmed speed
    - Override values have configurable limits and increments in
 config.h.
 - Feature: Realtime toggle overrides for spindle stop, flood coolant,
 and optionally mist coolant
    - Spindle stop: Enables and disables spindle during a feed hold.
 Automatically restores last spindles state.
    - Flood and mist coolant: Immediately toggles coolant state until
 next toggle or g-code coolant command.
 - Feature: Jogging mode! Incremental and absolute modes supported.
    - Grbl accepts jogging-specific commands like $J=X100F50. An axis
 word and feed rate are required. G20/21 and G90/G91 commands are
 accepted.
    - Jog motions can be canceled at any time by a feed hold `!`
 command. The buffer is automatically flushed. (No resetting required).
    - Jog motions do not alter the g-code parser state so GUIs don’t
 have to track what they changed and correct it.
 - Feature: Laser mode setting. Allows Grbl to execute continuous
 motions with spindle speed and state changes.
 - Feature: Significantly improved status reports. Overhauled to cram in
 more meaningful data and still make it smaller on average.
    - All available data is now sent by default, but does not appear if
 it doesn’t change or is not active.
    - Machine position(MPos) or work position(WPos) is reported but not
 both at the same time. Instead, the work coordinate offsets (WCO)are
 sent intermittently whenever it changes or refreshes after 10-30 status
 reports. Position vectors are easily computed by WPos  = MPos - WCO.
    - All data has changed in some way. Details of changes are in the
 markdown documents and wiki.
 - Feature: 16 new realtime commands to control overrides. All in
 extended-ASCII character space.
    - While they are not easily typeable and requires a GUI, they can’t
 be accidentally triggered by some latent character in the g-code
 program and have tons of room for expansion.
 - Feature: New substates for HOLD and SAFETY DOOR. A `:x` is appended
 to the state, where `x` is an integer and indicates a substate.
    - For example, each integer of a door state describes in what phase
 the machine is in during parking. Substates are detailed in the
 documentation.
 - Feature: With the alarm codes, homing and probe alarms have been
 expanded with more codes to provide more exact feedback on what caused
 the alarm.
 - Feature: New hard limit check upon power-up or reset. If detected, a
 feedback message to check the limit switches sent immediately after the
 welcome message.
    - May be disabled in config.h.
 - OEM feature: Enable/disable `$RST=` individual commands based on
 desired behavior in config.h.
 - OEM feature: Configurable EEPROM wipe to prevent certain data from
 being deleted during firmware upgrade to a new settings version or
 `RST=*` command.
 - OEM feature: Enable/disable the `$I=` build info write string with
 external EEPROM write example sketch.
    - This prevents a user from altering the build info string in
 EEPROM. This requires the vendor to write the string to EEPROM via
 external means. An Arduino example sketch is provided to accomplish
 this. This would be useful for contain product data that is
 retrievable.
 - Tweak: All feedback has been drastically trimmed to free up flash
 space for the v1.0 release.
    - The `$` help message is just one string, listing available
 commands.
    - The `$$` settings printout no longer includes descriptions. Only
 the setting values. (Sorry it’s this or remove overrides!)
    - Grbl `error:` and `ALARM:` responses now only contain codes. No
 descriptions. All codes are explained in documentation.
    - Grbl’s old feedback style may be restored via a config.h, but
 keep in mind that it will likely not fit into the Arduino’s flash space.
 - Tweak: Grbl now forces a buffer sync or stop motion whenever a g-code
 command needs to update and write a value to EEPROM or changes the work
 coordinate offset.
    - This addresses two old issues in all prior Grbl versions. First,
 an EEPROM write requires interrupts to be disabled, including stepper
 and serial comm. Steps can be lost and data can be corrupted. Second,
 the work position may not be correlated to the actual machine position,
 since machine position is derived from the actual current execution
 state, while work position is based on the g-code parser offset state.
 They are usually not in sync and the parser state is several motions
 behind. This forced sync ensures work and machine positions are always
 correct.
    - This behavior can be disabled through a config.h option, but it’s
 not recommended to do so.
 - Tweak: To make status reports standardized, users can no longer
 change what is reported via status report mask, except for only
 toggling machine or work positions.
    - All other data fields are included in the report and can only be
 disabled through the config.h file. It’s not recommended to alter this,
 because GUIs will be expecting this data to be present and may not be
 compatible.
 - Tweak: Homing cycle and parking motion no longer report a negative
 line number in a status report. These will now not report a line number
 at all.
 - Tweak: New `[Restoring spindle]` message when restoring from a
 spindle stop override. Provides feedback what Grbl is doing while the
 spindle is powering up and a 4.0 second delay is enforced.
 - Tweak: Override values are reset to 100% upon M2/30. This behavior
 can be disabled in config.h
 - Tweak: The planner buffer size has been reduced from 18 to 16 to free
 up RAM for tracking and controlling overrides.
 - Tweak: TX buffer size has been increased from 64 to 90 bytes to
 improve status reporting and overall performance.
 - Tweak: Removed the MOTION CANCEL state. It was redundant and didn’t
 affect Grbl’s overall operation by doing so.
 - Tweak: Grbl’s serial buffer increased by +1 internally, such that 128
 bytes means 128, not 127 due to the ring buffer implementation. Long
 overdue.
 - Tweak: Altered sys.alarm variable to be set by alarm codes, rather
 than bit flags. Simplified how it worked overall.
 - Tweak: Planner buffer and serial RX buffer usage has been combined in
 the status reports.
 - Tweak: Pin state reporting has been refactored to report only the
 pins “triggered” and nothing when not “triggered”.
 - Tweak: Current machine rate or speed is now included in every report.
 - Tweak: The work coordinate offset (WCO) and override states only need
 to be refreshed intermittently or reported when they change. The
 refresh rates may be altered for each in the config.h file with
 different idle and busy rates to lessen Grbl’s load during a job.
 - Tweak: For temporary compatibility to existing GUIs until they are
 updated, an option to revert back to the old style status reports is
 available in config.h, but not recommended for long term use.
 - Tweak: Removed old limit pin state reporting option from config.h in
 lieu of new status report that includes them.
 - Tweak: Updated the defaults.h file to include laser mode, altered
 status report mask, and fix an issue with a missing invert probe pin
 default.
 - Refactor: Changed how planner line data is generated and passed to
 the planner and onto the step generator. By making it a struct
 variable, this saved significant flash space.
 - Refactor: Major re-factoring of the planner to incorporate override
 values and allow for re-calculations fast enough to immediately take
 effect during operation. No small feat.
 - Refactor: Re-factored the step segment generator for re-computing new
 override states.
 - Refactor: Re-factored spindle_control.c to accommodate the spindle
 speed overrides and laser mode.
 - Refactor: Re-factored parts of the codebase for a new jogging mode.
 Still under development though and slated to be part of the official
 v1.0 release. Hang tight.
 - Refactor: Created functions for computing a unit vector and value
 limiting based on axis maximums to free up more flash.
 - Refactor: The spindle PWM is now set directly inside of the stepper
 ISR as it loads new step segments.
 - Refactor: Moved machine travel checks out of soft limits function
 into its own since jogging uses this too.
 - Refactor: Removed coolant_stop() and combined with
 coolant_set_state().
 - Refactor: The serial RX ISR forks off extended ASCII values to
 quickly assess the new override realtime commands.
 - Refactor: Altered some names of the step control flags.
 - Refactor: Improved efficiency of the serial RX get buffer count
 function.
 - Refactor: Saved significant flash by removing and combining print
 functions. Namely the uint8 base10 and base2 functions.
 - Refactor: Moved the probe state check in the main stepper ISR to
 improve its efficiency.
 - Refactor: Single character printPgmStrings() went converted to direct
 serial_write() commands to save significant flash space.
 - Documentation: Detailed Markdown documents on error codes, alarm
 codes, messages, new real-time commands, new status reports, and how
 jogging works. More to come later and will be posted on the Wiki as
 well.
 - Documentation: CSV files for quick importing of Grbl error and alarm
 codes.
 - Bug Fix: Applied v0.9 master fixes to CoreXY homing.
 - Bug Fix: The print float function would cause Grbl to crash if a
 value was 1e6 or greater. Increased the buffer by 3 bytes to help
 prevent this in the future.
 - Bug Fix: Build info and startup string EEPROM restoring was not
 writing the checksum value.
 - Bug Fix: Corrected an issue with safety door restoring the proper
 spindle and coolant state. It worked before, but breaks with laser mode
 that can continually change spindle state per planner block.
 - Bug Fix: Move system position and probe position arrays out of the
 system_t struct. Ran into some compiling errors that were hard to track
 down as to why. Moving them out fixed it.
--- a/doc/markdown/change_summary.md
+++ b/doc/markdown/change_summary.md
@ -0,0 +1,106 @@
 ### _Grbl v1.1  - Change Summary_
 --------
 ### _Specific details are available in the other markdown documents._
 --------
 #### GUI Interface Tweaks from Grbl v0.9
 Grbl v1.1's interface protocol has been tweaked in the attempt to make GUI development cleaner, clearer, and hopefully easier. All messages are designed to be deterministic without needing to know the context of the message. Each can be inferred to a much greater degree than before just by the message type, which are all listed below.
 - `ok` / `error:x` : Normal send command and execution response acknowledgement. Used for streaming.
 - `< >` : Enclosed chevrons contains status report data.
 - `Grbl X.Xx ['$' for help]` : Welcome message indicates initialization.
 - `ALARM:x` : Indicates an alarm has been thrown. Grbl is now in an alarm state.
 - `$x=val` and `$Nx=line` indicate a settings printout from a `$` and `$N` user query, respectively.
 - `[MSG:]` : Indicates a non-queried feedback message.
 - `[GC:]` : Indicates a queried `$G` g-code state message.
 - `[HLP:]` : Indicates the help message.
 - `[G54:]`, `[G55:]`, `[G56:]`, `[G57:]`, `[G58:]`, `[G59:]`, `[G28:]`, `[G30:]`, `[G92:]`, `[TLO:]`, and `[PRB:]` messages indicate the parameter data printout from a `$#` user query.
 - `[VER:]` : Indicates build info and string from a `$I` user query.
 - `[echo:]` : Indicates an automated line echo from a pre-parsed string prior to g-code parsing. Enabled by config.h option.
 - `>G54G20:ok` : The open chevron indicates startup line execution. The `:ok` suffix shows it executed correctly without adding an unmatched `ok` response on a new line.
 In addition, all `$x=val` settings, `error:`, and `ALARM:` messages no longer contain human-readable strings, but rather codes that are defined in other documents. The `$` help message is also reduced to just showing the available commands. Doing this saves incredible amounts of flash space. Otherwise, the new overrides features would not have fit.
 On a final note, these interface tweaks came about out of necessity, because more data is being sent back from Grbl, it is capable of doing many more things, and flash space is at a premium. It's not intended to be altered again in the near future, if at all. This is likely the only and last major change to this. If you have any comments or suggestions before Grbl v1.1 goes to master, please do immediately so we can all vet the new alteration before its installed.
 ----
 #### Realtime Status Reports Changes from Grbl v0.9
 - Intent of changes is to make parsing cleaner, reduce transmitting overhead without effecting overall Grbl performance, and add more feedback data, which includes three new override values and real-time velocity.
 - Data fields are separated by `|` pipe delimiters, rather than `,` commas that were used to separate data values. This should help with parsing.
 - The ability to mask and add/remove data fields from status reports via the `$10` status report mask setting has been disabled. Only selecting `MPos:` or `WPos:` coordinates is allowed.
  - All available data is always sent to standardize the reports across all GUIs.
  - For unique situations, data fields can be removed by config.h macros, but it is highly recommended to not alter these.
 - `MPos:` OR `WPos:` are always included in a report, but not BOTH at the same time.
  - This reduces transmit overhead tremendously by removing upwards to 40 characters.
  - `WCO:0.000,10.000,2.500` A current work coordinate offset is now sent to easily convert between position vectors, where `WPos = MPos - WCO` for each axis.
    - `WCO:` is included immediately whenever a `WCO:` value changes or intermittently after every **X** status reports as a refresh. Refresh rates can dynamically vary from 10 to 30 (configurable) reports depending on what Grbl is doing.
    - `WCO:` is simply the sum of the work coordinate system, G92, and G43.1 tool length offsets.
    - Basically, a GUI just needs to retain the last `WCO:` and apply the equation to get the other position vector.
    - `WCO:` messages may only be disabled via a config.h compile-option, if a GUI wants to handle the work position calculations on its own to free up more transmit bandwidth.
  - Be aware of the following issue regarding `WPos:`.
    - In Grbl v0.9 and prior, there is an old outstanding bug where the `WPos:` work position reported may not correlate to what is executing, because `WPos:` is based on the g-code parser state, which can be several motions behind. Grbl v1.1 now forces the planner buffer to empty, sync, and stops motion whenever there is a command that alters the work coordinate offsets `G10,G43.1,G92,G54-59`. This is the simplest way to ensure `WPos:` is always correct. Fortunately, it's exceedingly rare that any of these commands are used need continuous motions through them.
    - A compile-time option is available to disable the planner sync and forced stop, but, if used, it's up to the GUI to handle this position correlation issue.
 - The `Hold` and `Door` states includes useful sub-state info via a `:` colon delimiter and an integer value. See descriptions for details.
 - Limit and other input pin reports have significantly changed to reduce transmit overhead.
  - The data type description is now just `Pn:`, rather than `Lim:000` or `Pin:000|0|0000`
  - It does not appear if no inputs are detected as triggered.
  - If an input is triggered, ```Pn:``` will be followed by a letter or set of letters of every triggered input pin. `XYZPDHRS` for the XYZ-axes limits, Probe, Door, Hold, soft-Reset, cycle Start pins, respectively.
  - For example, a triggered Z-limit and probe pin would report `Pn:ZP`.
 - Buffer data (planner and serial RX) reports have been tweaked and combined.
  - `Bf:15,128`. The first value is the available blocks in the planner buffer and the second is available bytes in the serial RX buffer.
  - Note that this is different than before, where it reported blocks/bytes "in-use", rather than "available". This change does not require a GUI to know how many blocks/bytes Grbl has been compiled with, which can be substantially different on a Grbl-Mega build.
 - Override reports are intermittent since they don't change often once set.
  - Overrides are included in every 10 or 20 status reports (configurable) depending on what Grbl is doing or, if an override value or toggle state changes, automatically in the next report.
  - There are two override fields:
    - `Ov:100,100,100` Organized as feed, rapid, and spindle speed overrides in percent.
    - `T:SFM` with each letter `S`, `F`, and `M` are defined as spindle stop active, flood coolant toggled, and mist coolant toggled, respectively.
 - Line numbers, when enabled in config.h, are omitted when:
  - No line number is passed to Grbl in a block.
  - Grbl is performing a system motion like homing, jogging, or parking.
  - Grbl is executing g-code block that does not contain a motion, like `G20G54` or `G4P1` dwell. (NOTE: Looking to fixing this later.)
 -------
 #### New Commands
 - `$SLP` - Grbl v1.1 now has a sleep mode that can be invoked by this command. It requires Grbl to be in either an IDLE or ALARM state. Once invoked, Grbl will de-energize all connected systems, including the spindle, coolant, and stepper drivers. It'll enter a suspend state that can only be exited by a reset. When reset, Grbl will re-initiatize in an ALARM state because the steppers were disabled and position can not be guaranteed.
 	-  NOTE: Grbl-Mega can invoke the sleep mode at any time, when the sleep timeout feature is enabled in config.h. It does so when Grbl has not received any external input after a timeout period.
 - 	`$J=line` New jogging commands. This command behaves much like a normal G1 command, but there are some key differences. Jog commands don't alter the g-code parser state, meaning a GUI doesn't have to manage it anymore. Jog commands may be queued and cancelled at any time, where they are automatically flushed from the planner buffer without requiring a reset. See the jogging documentation on how they work and how they may be used to implement a low-latency joystick or rotary dial.
 - Laser mode `$` setting - When enabled, laser mode will move through consecutive G1, G2, and G3 motion commands that have different spindle speed values without stopping. A spindle speed of zero will disable the laser without stopping as well. However, when spindle states change, like M3 or M5, stops are still enforced.
 	- NOTE: Parking motions are automatically disabled when laser mode is enabled to prevent burning.
--- a/doc/markdown/interface.md
+++ b/doc/markdown/interface.md
@ -0,0 +1,581 @@
 # Grbl Interface Basics
 The interface for Grbl is fairly simple and straightforward. With Grbl v1.1, steps have been taken to try to make it even easier for new users to get started, and for GUI developers to write their own custom interfaces to Grbl.
 In short, Grbl communicates through the serial interface on the Arduino. You just need to connect your Arduino to your computer with a USB cable. Use any standard serial terminal program to connect to Grbl, such as: the Arduino IDE serial monitor, Coolterm, puTTY, etc. Or use one of the many great Grbl GUIs out there in the Internet wild.
 Just about every user interaction with Grbl is performed by sending it a string of characters, followed by a carriage return. Grbl will then process the string, execute it accordingly, and then reply back with a response message to tell you how it went. These strings include sending Grbl: a G-code block to execute, commands to configure Grbl's system settings, to view how Grbl is doing, etc. At times, Grbl may not respond immediately. This happens only when Grbl is busy doing something else, or waiting for some room to clear in its look-ahead planner buffer so it can finish processing the previous line sent.
 In other words, both commands sent to Grbl and messages received from Grbl have a format of a single line of characters, terminated by a return. To provide more feedback on what Grbl is doing, additional messages may be "pushed" from Grbl to the user in response to a query or to let the user know something important just happened. Finally, an exception to the command and response interface are Grbl's real-time commands. These commands are single, special characters that may be sent to Grbl at any time to immediately alter or report what its doing and do not have a response message. See the [realtime commands] document to see what they are and how they work.
 #### Start Up Message
 **`Grbl X.Xx ['$' for help]`**
 The start up message always prints upon startup and after a reset. Whenever you see this message, this also means that Grbl has completed re-initializing all its systems, so everything starts out the same every time you use Grbl.
 * `X.Xx` indicates the major version number, followed by a minor version letter. The major version number indicates the general release, while the letter simply indicates a feature update or addition from the preceding minor version letter.
 * Bug fix revisions are tracked by the build info version number, printed when an `$I` command is sent. These revisions don't update the version number and are given by date revised in year, month, and day, like so `20160820`.
 #### Grbl `$` Help Message
 Every string Grbl receives is assumed to be a G-code block/line for it to execute, except for some special system commands Grbl uses for configuration, provide feedback to the user on what and how it's doing, or perform some task such as a homing cycle. To see a list of these system commands, type `$` followed by an enter, and Grbl will respond with:
 ```
 [HLP:$$ $# $G $I $N $x=val $Nx=line $J=line $SLP $C $X $H ~ ! ? ctrl-x]
 ```
 - _**NOTE:** Grbl v1.1's new override real-time commands are not included in the help message. They use the extended-ASCII character set, which are not easily type-able, and require a GUI that supports them. This is for two reasons: Establish enough characters for all of the overrides with extra for later growth, and prevent accidental keystrokes or characters in a g-code file from enacting an override inadvertently. _
 * Check out our [Configuring Grbl](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9) wiki page to find out what all of these commands mean and how to use them.
 ---------
 # Grbl Response Messages
 Every G-code block sent to Grbl and Grbl `$` system command that is terminated with a return will be parsed and processed by Grbl. Grbl will then respond either if it recognized the command with an `ok` line or if there was a problem with an `error` line.
 * **`ok`**: All is good! Everything in the last line was understood by Grbl and was successfully processed and executed.
  - If an empty line with only a return is sent to Grbl, it considers it a valid line and will return an `ok` too, except it didn't do anything.
 * **`error:X`**: Something went wrong! Grbl did not recognize the command and did not execute anything inside that message. The `X` is given as a numeric error code to tell you exactly what happened. The table below decribes every one of them.
 | ID | Error Code Description |
 |:-------------:|----|
 | **`1`** | G-code words consist of a letter and a value. Letter was not found. |
 | **`2`** | Numeric value format is not valid or missing an expected value. |
 | **`3`** | Grbl '$' system command was not recognized or supported. |
 | **`4`** | Negative value received for an expected positive value. |
 | **`5`** | Homing cycle is not enabled via settings. |
 | **`6`** | Minimum step pulse time must be greater than 3usec |
 | **`7`** | EEPROM read failed. Reset and restored to default values. |
 | **`8`** | Grbl '$' command cannot be used unless Grbl is IDLE. Ensures smooth operation during a job. |
 | **`9`** | G-code locked out during alarm or jog state |
 | **`10`** | Soft limits cannot be enabled without homing also enabled. |
 | **`11`** | Max characters per line exceeded. Line was not processed and executed. |
 | **`12`** | (Compile Option) Grbl '$' setting value exceeds the maximum step rate supported. |
 | **`13`** | Safety door detected as opened and door state initiated. |
 | **`14`** | (Grbl-Mega Only) Build info or startup line exceeded EEPROM line length limit. |
 | **`15`** | Jog target exceeds machine travel. Command ignored. |
 | **`16`** | Jog command with no '=' or contains prohibited g-code. |
 | **`20`** | Unsupported or invalid g-code command found in block. |
 | **`21`** | More than one g-code command from same modal group found in block.|
 | **`22`** | Feed rate has not yet been set or is undefined. |
 | **`23`** | G-code command in block requires an integer value. |
 | **`24`** | Two G-code commands that both require the use of the `XYZ` axis words were detected in the block.|
 | **`25`** | A G-code word was repeated in the block.|
 | **`26`** | A G-code command implicitly or explicitly requires `XYZ` axis words in the block, but none were detected.|
 | **`27`**| `N` line number value is not within the valid range of `1` - `9,999,999`. |
 | **`28`** | A G-code command was sent, but is missing some required `P` or `L` value words in the line. |
 | **`29`** | Grbl supports six work coordinate systems `G54-G59`. `G59.1`, `G59.2`, and `G59.3` are not supported.|
 | **`30`**| The `G53` G-code command requires either a `G0` seek or `G1` feed motion mode to be active. A different motion was active.|
 | **`31`** | There are unused axis words in the block and `G80` motion mode cancel is active.|
 | **`32`** | A `G2` or `G3` arc was commanded but there are no `XYZ` axis words in the selected plane to trace the arc.|
 | **`33`** | The motion command has an invalid target. `G2`, `G3`, and `G38.2` generates this error, if the arc is impossible to generate or if the probe target is the current position.|
 | **`34`** | A `G2` or `G3` arc, traced with the radius definition, had a mathematical error when computing the arc geometry. Try either breaking up the arc into semi-circles or quadrants, or redefine them with the arc offset definition.|
 | **`35`** | A `G2` or `G3` arc, traced with the offset definition, is missing the `IJK` offset word in the selected plane to trace the arc.|
 | **`36`** | There are unused, leftover G-code words that aren't used by any command in the block.|
 | **`37`** | The `G43.1` dynamic tool length offset command cannot apply an offset to an axis other than its configured axis. The Grbl default axis is the Z-axis.|
 ----------------------
 # Grbl Push Messages
 Along with the response message to indicate successfully executing a line command sent to Grbl, Grbl provides additional push messages for important feedback of its current state or if something went horribly wrong. These messages are "pushed" from Grbl and may appear at anytime. They are usually in response to a user query or some system event that Grbl needs to tell you about immediately. These push messages are organized into five general classes:
 - **_ALARM messages_** - Means an emergency mode has been enacted and shut down normal use.
 - **_'$' settings messages_** - Contains the type and data value for a Grbl setting.
 - **_Feedback messages_** - Contains general feedback and can provide useful data.
 - **_Startup line execution_** - Indicates a startup line as executed with the line itself and how it went.
 - **_Real-time status reports_** - Contains current run data like state, position, and speed.
 ------
 #### Alarm Message
 Alarm is an emergency state. Something has gone terribly wrong when these occur. Typically, they are caused by limit error when the machine has moved or wants to move outside the machine travel and crash into the ends. They also report problems if Grbl is lost and can't guarantee positioning or a probe command has failed. Once in alarm-mode, Grbl will lock out all g-code functionality and accept only a small set of commands. It may even stop everything and force you to acknowledge the problem until you issue Grbl a reset. While in alarm-mode, the user can override the alarm manually with a specific command, which then re-enables g-code so you can move the machine again. This ensures the user knows about the problem and has taken steps to fix or account for it.
 Similar to error messages, all alarm messages are sent as  **`ALARM:X`**, where `X` is an alarm code to tell you exacly what caused the alarm. The table below describes the meaning of each alarm code.
 | ID | Alarm Code Description |
 |:-------------:|----|
 | **`1`** | Hard limit triggered. Machine position is likely lost due to sudden and immediate halt. Re-homing is highly recommended. |
 | **`2`** | G-code motion target exceeds machine travel. Machine position safely retained. Alarm may be unlocked. |
 | **`3`** | Reset while in motion. Grbl cannot guarantee position. Lost steps are likely. Re-homing is highly recommended. |
 | **`4`** | Probe fail. The probe is not in the expected initial state before starting probe cycle, where G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered. |
 | **`5`** | Probe fail. Probe did not contact the workpiece within the programmed travel for G38.2 and G38.4. |
 | **`6`** | Homing fail. Reset during active homing cycle. |
 | **`7`** | Homing fail. Safety door was opened during active homing cycle. |
 | **`8`** | Homing fail. Cycle failed to clear limit switch when pulling off. Try increasing pull-off setting or check wiring. |
 | **`9`** | Homing fail. Could not find limit switch within search distance. Defined as `1.5 * max_travel` on search and `5 * pulloff` on locate phases. |
 -------
 #### Grbl `$` Settings Message
 When a push message starts with a `$`, this indicates Grbl is sending a setting and its configured value. There are only two types of settings messages: a single setting and value `$x=val` and a startup string setting `$Nx=line`. See [Configuring Grbl v1.x] document if you'd like to learn how to write these values for your machine.
 - `$x=val` will only appear when the user queries to print all of Grbl's settings via the `$$` print settings command. It does so sequentially and completes with an `ok`.
  - In prior versions of Grbl, the `$` settings included a short description of the setting immediately after the value. However, due to flash restrictions, most human-readable strings were removed to free up flash for the new override features in Grbl v1.1. In short, it was these strings or overrides, and overrides won. Keep in mind that once these values are set, they usually don't change, and GUIs will likely provide the assistance of translating these codes for users.
  - _**NOTE for GUI developers:**_ _As with the error and alarm codes, settings codes are available in an easy to parse CSV file in the `/doc/csv` folder. These are continually updated._
  - The `$$` settings print out is shown below and the following describes each setting.
    ```
 $0=10
 $1=25
 $2=0
 $3=0
 $4=0
 $5=0
 $6=0
 $10=255
 $11=0.010
 $12=0.002
 $13=0
 $20=0
 $21=0
 $22=0
 $23=0
 $24=25.000
 $25=500.000
 $26=250
 $27=1.000
 $30=1000.
 $31=0.
 $32=0
 $100=250.000
 $101=250.000
 $102=250.000
 $110=500.000
 $111=500.000
 $112=500.000
 $120=10.000
 $121=10.000
 $122=10.000
 $130=200.000
 $131=200.000
 $132=200.000
 ok
 ```
 | `$x` Code | Setting Description, Units |
 |:-------------:|----|
 | **`0`** | Step pulse time, microseconds |
 | **`1`** | Step idle delay, milliseconds |
 | **`2`** | Step pulse invert, mask |
 | **`3`** | Step direction invert, mask |
 | **`4`** | Invert step enable pin, boolean |
 | **`5`** | Invert limit pins, boolean |
 | **`6`** | Invert probe pin, boolean |
 | **`10`** | Status report options, mask |
 | **`11`** | Junction deviation, millimeters |
 | **`12`** | Arc tolerance, millimeters |
 | **`13`** | Report in inches, boolean |
 | **`20`** | Soft limits enable, boolean |
 | **`21`** | Hard limits enable, boolean |
 | **`22`** | Homing cycle enable, boolean |
 | **`23`** | Homing direction invert, mask |
 | **`24`** | Homing locate feed rate, mm/min |
 | **`25`** | Homing search seek rate, mm/min  |
 | **`26`** | Homing switch debounce delay, milliseconds |
 | **`27`** | Homing switch pull-off distance, millimeters |
 | **`30`** | Maximum spindle speed, RPM |
 | **`31`** | Minimum spindle speed, RPM |
 | **`32`** | Laser-mode enable, boolean |
 | **`100`** | X-axis steps per millimeter |
 | **`101`** | Y-axis steps per millimeter |
 | **`102`** | Z-axis steps per millimeter |
 | **`110`** | X-axis maximum rate, mm/min |
 | **`111`** | Y-axis maximum rate, mm/min |
 | **`112`** | Z-axis maximum rate, mm/min |
 | **`120`** | X-axis acceleration, mm/sec^2 |
 | **`121`** | Y-axis acceleration, mm/sec^2 |
 | **`122`** | Z-axis acceleration, mm/sec^2 |
 | **`130`** | X-axis maximum travel, millimeters |
 | **`131`** | Y-axis maximum travel, millimeters |
 | **`132`** | Z-axis maximum travel, millimeters |
 - The other `$Nx=line` message is the print-out of a user-defined startup line, where `x` denotes the startup line order and ranges from `0` to `1` by default. The `line` denotes the startup line to be executed by Grbl upon reset or power-up, except during an ALARM.
  - When a user queries for the startup lines via a `$N` command, the following is sent by Grbl and completed by an `ok` response. The first line sets the initial startup work coordinate system to `G54`, while the second line is empty and does not execute.
  ```
  $N0=G54
  $N1=
  ok
  ```
 ------
 #### Feedback Messages
 Feedback messages provide non-critical information on what Grbl is doing, what it needs, and/or provide some non-real-time data for the user when queried. Not too complicated. Feedback message are always enclosed in `[]` brackets, except for the startup line execution message which begins with an open chevron character `>`.
 - **Non-Queried Feedback Messages:** These feedback messages that may appear at any time and is not part of a query are listed and described below. They are usually sent as an additional helpful acknowledgement of some event or command executed. These always start with a `[MSG:` to denote their type.
  - `[MSG:Reset to continue]` - Critical event message. Reset is required before Grbl accepts any other commands. This prevents ongoing command streaming and risking a motion before the alarm is acknowledged. Only hard or soft limit errors send this message immediately after the ALARM:x code.
  - `[MSG:‘$H’|’$X’ to unlock]`- Alarm state is active at initialization. This message serves as a reminder note on how to cancel the alarm state. All g-code commands and some ‘$’ are blocked until the alarm state is cancelled via homing `$H` or unlocking `$X`. Only appears immediately after the `Grbl` welcome message when initialized with an alarm. Startup lines are not executed at initialization if this message is present and the alarm is active.
  - `[MSG:Caution: Unlocked]` - Appears as an alarm unlock `$X` acknowledgement. An 'ok' still appears immediately after to denote the `$X` was parsed and executed. This message reminds the user that Grbl is operating under an unlock state, where startup lines have still not be executed and should be cautious and mindful of what they do. Grbl may not have retained machine position due to an alarm suddenly halting the machine.  A reset or re-homing Grbl is highly recommended as soon as possible, where any startup lines will be properly executed.
  - `[MSG:Enabled]` - Appears as a check-mode `$C` enabled acknowledgement. An 'ok' still appears immediately after to denote the `$C` was parsed and executed.
  - `[MSG:Disabled]` - Appears as a check-mode `$C` disabled acknowledgement. An 'ok' still appears immediately after to denote the `$C` was parsed and executed. Grbl is automatically reset afterwards to restore all default g-code parser states changed by the check-mode.
  - `[MSG:Check Door]` - This message appears whenever the safety door detected as open. This includes immediately upon a safety door switch detects a pin change or appearing after the welcome message, if the safety door is ajar when Grbl initializes after a power-up/reset.
    - If in motion and the safety door switch is triggered, Grbl will immediately send this message, start a feed hold, and place Grbl into a suspend with the DOOR state.
    - If not in motion and not at startup, the same process occurs without the feed hold.
    - If Grbl is in a DOOR state and already suspended, any detected door switch pin detected will generate this message, including a door close.
    - If this message appears at startup, Grbl will suspended into immediately into the DOOR state. The startup lines are executed immediately after the DOOR state is exited by closing the door and sending Grbl a resume command.
  - `[MSG:Check Limits]` - If Grbl detects a limit switch as triggered after a power-up/reset and hard limits are enabled, this will appear as a courtesy message immediately after the Grbl welcome message.
  - `[MSG:Pgm End]` - M2/30 program end message to denote g-code modes have been restored to defaults according to the M2/30 g-code description.
  - `[MSG:Restoring defaults]` - Appears as an acknowledgement message when restoring EEPROM defaults via a `$RST=` command. An 'ok' still appears immediately after to denote the `$RST=` was parsed and executed.
  - `[MSG:Sleeping]` - Appears as an acknowledgement message when Grbl's sleep mode is invoked by issuing a `$SLP` command when in IDLE or ALARM states. Note that Grbl-Mega may invoke this at any time when the sleep timer option has been enabled and the timeout has been exceeded. Grbl may only be exited by a reset in the sleep state and will automatically enter an alarm state since the steppers were disabled.
 	  - NOTE: Sleep will also invoke the parking motion, if it's enabled. However, if sleep is commanded during an ALARM, Grbl will not park and will simply de-energize everything and go to sleep.
 - **Queried Feedback Messages:**
  - `[GC:]` G-code Parser State Message
    - Initiated by the user via a `$G` command. Grbl replies as follows, where the `[GC:` denotes the message type and is followed by a separate `ok` to confirm the `$G` was executed.
     ```
     [GC:G0 G54 G17 G21 G90 G94 M0 M5 M9 T0 F0. S0.]
     ok
     ```
    - The shown g-code are the current modal states of Grbl's g-code parser. This may not correlate to what is executing since there are usually several motions queued in the planner buffer.
  - `[HLP:]` : Initiated by the user via a `$` print help command. The help message is shown below with a separate `ok` to confirm the `$` was executed.
    ```
    [HLP:$$ $# $G $I $N $x=val $Nx=line $J=line $C $X $H ~ ! ? ctrl-x]
    ok
    ```
  - The `$#` print parameter data query produces a large set of data which shown below and completed by an `ok` response message.
    - Each line of the printout is starts with the data type, a `:`, and followed by the data values. If there is more than one, the order is XYZ axes, separated by commas.
      ```
      [G54:0.000,0.000,0.000]
      [G55:0.000,0.000,0.000]
      [G56:0.000,0.000,0.000]
      [G57:0.000,0.000,0.000]
      [G58:0.000,0.000,0.000]
      [G59:0.000,0.000,0.000]
      [G28:0.000,0.000,0.000]
      [G30:0.000,0.000,0.000]
      [G92:0.000,0.000,0.000]
      [TLO:0.000]
      [PRB:0.000,0.000,0.000:0]
      ok
      ```
    - The `PRB:` probe parameter message includes an additional `:` and suffix value is a boolean. It denotes whether the last probe cycle was successful or not.
  - `[VER:]` : Indicates build info and string from a `$I` user query. The build info message is shown below with a separate `ok` to confirm the `$I` was executed.
      ```
      [VER:v1.1a.20160923:]
      ok
      ```
      - A string may appear after the `:` colon. It is a stored EEPROM string a user or OEM can place there for personal use or tracking purposes.
  - `[echo:]` : Indicates an automated line echo from a command just prior to being parsed and executed. May be enabled only by a config.h option. Often used for debugging communication issues. A typical line echo message is shown below. A separate `ok` will eventually appear to confirm the line has been parsed and executed, but may not be immediate as with any line command containing motions.
      ```
      [echo:G1X0.540Y10.4F100]
      ```
      - NOTE: The echoed line will have been pre-parsed a bit by Grbl. No spaces or comments will appear and all letters will be capitalized.
 ------
 #### Startup Line Execution
  - `>G54G20:ok` : The open chevron indicates a startup line has just executed. The startup line `G54G20` immediately follows the `>` character and is followed by an `:ok` response to indicate it executed successfully.
    - A startup line will execute upon initialization only if a line is present and if Grbl is not in an alarm state.
    - The `:ok` on the same line is intentional. It prevents this `ok` response from being counted as part of a stream, because it is not tied to a sent command, but an internally-generated one.
    - There should always be an appended `:ok` because the startup line is checked for validity before it is stored in EEPROM. In the event that it's not, Grbl will print `>G54G20:error:X`, where `X` is the error code explaining why the startup line failed to execute.
    - In the rare chance that there is an EEPROM read error, the startup line execution will print `>:error:7` with no startup line and a error code `7` for a read fail. Grbl will also automatically wipe and try to restore the problematic EEPROM.
 ------
 #### Real-time Status reports
 - Contains real-time data of Grbl’s state, position, and other data required independently of the stream.
 - Categorized as a real-time message, where it is a separate message that should not be counted as part of the streaming protocol. It may appear at any given time.
 - A status report is initiated by sending Grbl a '?' character.
  - Like all real-time commands, the '?' character is intercepted and never enters the serial buffer. It's never a part of the stream and can be sent at any time.
  - Grbl will generate and transmit a report within ~5-20 milliseconds.
  - Every ’?’ command sent by a GUI is not guaranteed with a response. The following are the current scenarios when Grbl may not immediately or ignore a status report request. _NOTE: These may change in the future and will be documented here._
    - If two or more '?' queries are sent before the first report is generated, the additional queries are ignored.
    - A soft-reset commanded clears the last status report query.
    - When Grbl throws a critical alarm from a limit violation. A soft-reset is required to resume operation.
    - During a homing cycle.
 - **Message Construction:**
  - A message is a single line of ascii text, completed by a carriage return and line feed.
  - `< >` Chevrons uniquely enclose reports to indicate message type.
  - `|` Pipe delimiters separate data fields inside the report.
  - The first data field is an exception to the following data field rules. See 'Machine State' description for details.
  - All remaining data fields consist of a data type followed by a `:` colon delimiter and data values. `type:value(s)`
  - Data values are given either as as one or more pre-defined character codes to indicate certain states/conditions or as numeric values, which are separated by a `,` comma delimiter when more than one is present. Numeric values are also in a pre-defined order and units of measure.
  - The first (Machine State) and second (Current Position) data fields are always included in every report.
  - Assume any following data field may or may not exist and can be in any order. The `$10` status report mask setting can alter what data is present and certain data fields can be reported intermittently (see descriptions for details.)
  - The `$13` report inches settings alters the units of some data values. `$13=0` false indicates mm-mode, while `$13=1` true indicates inch-mode reporting. Keep note of this setting and which report values can be altered.
 - **Data Field Descriptions:**
    - **Machine State:**
      - Valid states types:  `Idle, Run, Hold, Jog, Alarm, Door, Check, Home, Sleep`
      - Sub-states may be included via `:` a colon delimiter and numeric code.
      - Current sub-states are:
        - `Hold:0` Hold complete. Ready to resume.
        - `Hold:1` Hold in-progress. Reset will throw an alarm.
        - `Door:0` Door closed. Ready to resume.
        - `Door:1` Machine stopped. Door still ajar. Can't resume until closed.
        - `Door:2` Door opened. Hold (or parking retract) in-progress. Reset will throw an alarm.
        - `Door:3` Door closed and resuming. Restoring from park, if applicable. Reset will throw an alarm.
      - This data field is always present as the first field.
    - **Current Position:**
        - Depending on `$10` status report mask settings, position may be sent as either:
          - `MPos:0.000,-10.000,5.000` machine position or
          - `WPos:-2.500,0.000,11.000` work position
        - Three position values are given in the order of X, Y, and Z. A fourth position value may exist in later versions for the A-axis.
        - `$13` report inches user setting effects these values and is given as either mm or inches.
        - This data field is always present as the second field.
    - **Work Coordinate Offset:**
        - `WCO:0.000,1.551,5.664` is the current work coordinate offset of the g-code parser, which is the sum of the current work coordinate system, G92 offsets, and G43.1 tool length offset.
        - Machine position and work position are related by this simple equation per axis: `WPos = MPos - WCO`
        - Values are given in the order of the X,Y, and Z axes offsets. A fourth offset value may exist in later versions for the A-axis.
        - `$13` report inches user setting effects these values and is given as either mm or inches.
        - `WCO:` values don't change often during a job once set and only requires intermittent refreshing.
        - This data field appears:
          - In every 10 or 30 (configurable 1-255) status reports, depending on if Grbl is in a motion state or not.
          - Immediately in the next report, if an offset value has changed.
          - In the first report after a reset/power-cycle.
        - This data field will not appear if:
          - It is disabled in the config.h file. No `$` mask setting available.
          - The refresh counter is in-between intermittent reports.       
    - **Buffer State:**
        - `Bf:15,128`. The first value is the number of available blocks in the planner buffer and the second is number of available bytes in the serial RX buffer.
        - The usage of this data is generally for debugging an interface, but is known to be used to control some GUI-specific tasks. While this is disabled by default, GUIs should expect this data field to appear, but they may ignore it, if desired.
        - NOTE: The buffer state values changed from showing "in-use" blocks or bytes to "available". This change does not require the GUI knowing how many block/bytes Grbl has been compiled with.
        - This data field appears:
          - In every status report when enabled. It is disabled in the settings mask by default.
        - This data field will not appear if:
          - It is disabled by the `$` status report mask setting or disabled in the config.h file.
    - **Line Number:**
        - `Ln:99999` indicates line 99999 is currently being executed. This differs from the `$G` line `N` value since the parser is usually queued few blocks behind execution.
        - Compile-time option only because of memory requirements. However, if a GUI passes indicator line numbers onto Grbl, it's very useful to determine when Grbl is executing them.
        - This data field will not appear if:
          - It is disabled in the config.h file. No `$` mask setting available.
          - The line number reporting not enabled in config.h. Different option to reporting data field.
          - No line number or `N0` is passed with the g-code block.
          - Grbl is homing, jogging, parking, or performing a system task/motion.
          - There is no motion in the g-code block like a `G4P1` dwell. (May be fixed in later versions.)
    - **Current Rate:**
        - `F:1000.` indicates current actual feed rate (speed) of the executing motion. Depending on machine max rate settings and acceleration, this value may not be the programmed rate.
        - Value units, either in mm/min or inches/min, is dependent on the `$` report inches user setting.
        - As a operational note, reported rate is typically 30-50 msec behind actual position reported.
        - This data field will not appear if:
          - It is disabled in the config.h file. No `$` mask setting available.
    - **Input Pin State:**
        - `Pn:XYZPDHRS` indicates which input pins Grbl has detected as 'triggered'.
        - Pin state is evaluated every time a status report is generated. All input pin inversions are appropriately applied to determine 'triggered' states.
        - Each letter of `XYZPDHRS` denotes a particular 'triggered' input pin.
          - `X Y Z` XYZ limit pins, respectively
          - `P` the probe pin.
          - `D H R S` the door, hold, soft-reset, and cycle-start pins, respectively.
          - Example: `Pn:PZ` indicates the probe and z-limit pins are 'triggered'.
          - Note: `A` may be added in later versions for an A-axis limit pin.
        - Assume input pin letters are presented in no particular order.
        - One or more 'triggered' pin letter(s) will always be present with a `Pn:` data field.
        - This data field will not appear if:
          - It is disabled in the config.h file. No `$` mask setting available.
          - No input pins are detected as triggered.
    - **Override Values:**
        - `Ov:100,100,100` indicates current override values in percent of programmed values for feed, rapids, and spindle speed, respectively.
        - Override values don't change often during a job once set and only requires intermittent refreshing. This data field appears:
          - After 10 or 20 (configurable 1-255) status reports, depending on is in a motion state or not.
          - If an override value has changed, this data field will appear immediately in the next report. However, if `WCO:` is present, this data field will be delayed one report.
          - In the second report after a reset/power-cycle.
        - This data field will not appear if:
          - It is disabled in the config.h file. No `$` mask setting available.
          - The override refresh counter is in-between intermittent reports.
          - `WCO:` exists in current report during refresh. Automatically set to try again on next report.
    - **Toggle Overrides:**
      - `T:SFM` indicates a toggle override is in effect or has been commanded.
      - Like the pin state field, each letter denotes a particular toggle override.
        - `S` indicates the spindle stop toggle override is in effect. It will appear as long as the spindle stop override is active.
        - `F` indicates the flood coolant toggle override was activated. It will only appear once after it has executed the coolant state change.
        - `M` indicates the mist coolant toggle override was activated, if mist coolant is enabled via config.h. It will only appear once after it has executed the coolant state change.
      - Assume toggle override letters are presented in no particular order.
      - One or more active toggle override letter(s) will always be present with a `T:` data field.
      - This data field appears:
        - If a toggle override is active or has recently executed and only when the override values field is also present (see override value field rules).
      - This data field will not appear if:
        - If no toggle override is active or has been executed.
        - It is disabled in the config.h file. No `$` mask setting available.
        - If override refresh counter is in-between intermittent reports.
        - `WCO:` exists in current report during refresh. Automatically set to try again on next report.
 -------
 # Message Summary
 Grbl v1.1's interface protocol has been tweaked in the attempt to make GUI development cleaner, clearer, and hopefully easier. All messages are designed to be deterministic without needing to know the context of the message. Each can be inferred to a much greater degree than before just by the message type, which are all listed below.
 - `ok` / `error:x` : Normal send command and execution response acknowledgement. Used for streaming.
 - `< >` : Enclosed chevrons contains status report data.
 - `Grbl X.Xx ['$' for help]` : Welcome message indicates initialization.
 - `ALARM:x` : Indicates an alarm has been thrown. Grbl is now in an alarm state.
 - `$x=val` and `$Nx=line` indicate a settings printout from a `$` and `$N` user query, respectively.
 - `[MSG:]` : Indicates a non-queried feedback message.
 - `[GC:]` : Indicates a queried `$G` g-code state message.
 - `[HLP:]` : Indicates the help message.
 - `[G54:]`, `[G55:]`, `[G56:]`, `[G57:]`, `[G58:]`, `[G59:]`, `[G28:]`, `[G30:]`, `[G92:]`, `[TLO:]`, and `[PRB:]` messages indicate the parameter data printout from a `$#` user query.
 - `[VER:]` : Indicates build info and string from a `$I` user query.
 - `[echo:]` : Indicates an automated line echo from a pre-parsed string prior to g-code parsing. Enabled by config.h option.
 - `>G54G20:ok` : The open chevron indicates startup line execution. The `:ok` suffix shows it executed correctly without adding an unmatched `ok` response on a new line.
 On a final note, this interface tweak came about out of necessity, as more data is being sent back from Grbl and it is capable of doing many more things. It's not intended to be altered again in the near future, if at all. This is likely the only and last major change to this. If you have any comments or suggestions before Grbl v1.1 goes to master, please do immediately so we can all vet the new alteration before its installed.
--- a/doc/markdown/jogging.md
+++ b/doc/markdown/jogging.md
@ -0,0 +1,90 @@
 # Grbl v1.1 Jogging
 ## How to Use
 Executing a jog requires a specific command structure, as described below:
 - The first three characters must be '$J=' to indicate the jog.
 - The jog command follows immediate after the '=' and works like a normal G1 command.
 - Feed rate is only interpreted in G94 units per minute. A prior G93 state is ignored during jog.
 - Required words:
   - XYZ: One or more axis words with target value.
   - F - Feed rate value. NOTE: Each jog requires this value and is not treated as modal.
 - Optional words: Jog executes based on current G20/G21 and G90/G91 g-code parser state. If one of the following optional words is passed, that state is overridden for one command only.
   - G20 or G21 - Inch and millimeter mode
   - G90 or G91 - Absolute and incremental distances
   - G53 - Move in machine coordinates
 - All other g-codes, m-codes, and value words are not accepted in the jog command.
 - Spaces and comments are allowed in the command. These are removed by the pre-parser.
 - Example: G21 and G90 are active modal states prior to jogging. These are sequential commands.
    - `$J=X10.0 Y-1.5` will move to X=10.0mm and Y=-1.5mm in work coordinate frame (WPos).
    - `$J=G91 G20 X0.5` will move +0.5 inches (12.7mm) to X=22.7mm (WPos). Note that G91 and G20 are only applied to this jog command.
    - `$J=G53 Y5.0` will move the machine to Y=5.0mm in the machine coordinate frame (MPos). If the work coordinate offset for the y-axis is 2.0mm, then Y is 3.0mm in (WPos).
 Jog commands behave almost identically to normal g-code streaming. Every jog command will
 return an 'ok' when the jogging motion has been parsed and is setup for execution. If a
 command is not valid, Grbl will return an 'error:'. Multiple jogging commands may be
 queued in sequence.
 The main differences are:  
 - During a jog, Grbl will report a 'Jog' state while executing the jog.
 - A jog command will only be accepted when Grbl is in either the 'Idle' or 'Jog' states.
 - Jogging motions may not be mixed with g-code commands while executing, which will return a lockout error, if attempted.
 - All jogging motion(s) may be cancelled at anytime with a simple jog cancel realtime command or a feed hold or safety door event. Grbl will automatically flush Grbl's internal buffers of any queued jogging motions and return to the 'Idle' state. No soft-reset required.
 - If soft-limits are enabled, jog commands that exceed the machine travel simply does not execute the command and return an error, rather than throwing an alarm in normal operation.
 - IMPORTANT: Jogging does not alter the g-code parser state. Hence, no g-code modes need to be explicitly managed, unlike previous ways of implementing jogs with commands like 'G91G1X1F100'. Since G91, G1, and F feed rates are modal and if they are not changed back prior to resuming/starting a job, a job may not run how its was intended and result in a crash.
 ------
 ## Joystick Implementation
 Jogging in Grbl v1.1 is generally intended to address some prior issues with old bootstrapped jogging methods. Unfortunately, the new Grbl jogging is not a complete solution. Flash and memory restrictions prevent the original envisioned implementation, but most of these can be mimicked by the following suggested methodology. 
 With a combination of the new jog cancel and moving in `G91` incremental mode, the following implementation can create low latency feel for an analog joystick or similar control device.
 - Basic Implementation Overview: 
  - Create a loop to read the joystick signal and translate it to a desired jog motion vector.
  - Send Grbl a very short `G91` incremental distance jog command with a feed rate based on the joystick throw.
  - Wait for an 'ok' acknowledgement before restarting the loop.
  - Continually read the joystick input and send Grbl short jog motions to keep Grbl's planner buffer full.
  - If the joystick is returned to its neutral position, stop the jog loop and simply send Grbl a jog cancel real-time command. This will stop motion immediately somewhere along the programmed jog path with virtually zero-latency and automatically flush Grbl's planner queue. It's not advised to use a feed hold to cancel a jog, as it can lead to inadvertently suspending Grbl if its sent after returning to the IDLE state.
 The overall idea is to minimize the total distance in the planner queue to provide a low-latency feel to joystick control. The main trick is ensuring there is just enough distance in the planner queue, such that the programmed feed rate is always met. How to compute this will be explain later. In practice, most machines will have a 0.5-1.0 second latency. When combined with the immediate jog cancel command, joystick interaction can be quite enjoyable and satisfying.
 However, please note, if a machine has a low acceleration and is being asked to move at a high programmed feed rate, joystick latency can get up to a handful of seconds. It may sound bad, but this is how long it'll take for a low acceleration machine, traveling at a high feed rate, to slow down to a stop. The argument can be made for a low acceleration machine that you really shouldn't be jogging at a high feed rate. It is difficult for a user to gauge where the machine will come to a stop. You risk overshooting your target destination, which can result in an expensive or dangerous crash. 
 One of the advantages of this approach is that a GUI can deterministically track where Grbl will go by the jog commands it has already sent to Grbl. As long as a jog isn't cancelled, every jog command is guaranteed to execute. In the event a jog cancel is invoked, the GUI would just need to refresh their internal position from a status report after Grbl has cleared planner buffer and returned to the IDLE (or DOOR, if ajar) state from the JOG state. This stopped position will always be somewhere along the programmed jog path. If desired, jogging can then be quickly and easily restarted with a new tracked path.
 In combination with `G53` move in machine coordinates, a GUI can restrict jogging from moving into "keep-out" zones inside the machine space. This can be very useful for avoiding crashing into delicate probing hardware, workholding mechanisms, or other fixed features inside machine space that you want to avoid.
 #### How to compute incremental distances
 The quickest and easiest way to determine what the length of a jog motion needs to be to minimize latency are defined by the following equations.
 `s = v * dt` - Computes distance traveled for next jog command.
 where:  
 - `s` - Incremental distance of jog command.
 - `dt` - Estimated execution time of a single jog command in seconds.  
 - `v` - Current jog feed rate in **mm/sec**, not mm/min. Less than or equal to max jog rate.
 - `N` - Number of Grbl planner blocks (`N=15`)
 - `T = dt * N` - Computes total estimated latency in seconds.
 The time increment `dt` may be defined to whatever value you need. Obviously, you'd like the lowest value, since that translates to lower overall latency `T`. However, it is constrained by two factors.
 - `dt > 10ms` - The time it takes Grbl to parse and plan one jog command and receive the next one. Depending on a lot of factors, this can be around 1 to 5 ms. To be conservative, `10ms` is used. Keep in mind that on some systems, this value may still be greater than `10ms` due to round-trip communication latency.
 - `dt > v^2 / (2 * a * (N-1))` - The time increment needs to be large enough to ensure the jog feed rate will be acheived. Grbl always plans to a stop over the total distance queued in the planner buffer. This is primarily to ensure the machine will safely stop if a disconnection occurs. This equation simply ensures that `dt` is big enough to satisfy this constraint. 
 	- For simplicity, use the max jog feed rate for `v` in mm/sec and the smallest acceleration setting between the jog axes being moved in mm/sec^2.
 	- For a lower latency, `dt` can be computed for each jog motion, where `v` is the current rate and `a` is the max acceleration along the jog vector. This is very useful if traveling a very slow speeds to locate a part zero. The `v` rate would be much lower in this scenario and the total latency would decrease quadratically.
 In practice, most CNC machines will operate with a jogging time increment of `0.025 sec` < `dt` < `0.06 sec`, which translates to about a `0.4` to `0.9` second total latency when traveling at the max jog rate. Good enough for most people. 
 However, if jogging at a slower speed and a GUI adjusts the `dt` with it, you can get very close to the 0.1 second response time by human-interface guidelines for "feeling instantaneous". Not too shabby!
 With some ingenuity, this jogging methodology may be applied to different devices such as a rotary dial or touchscreen. An "inertial-feel", like swipe-scrolling on a smartphone or tablet, can be simulated by managing the jog rate decay and sending Grbl the associated jog commands. While this jogging implementation requires more initial work by a GUI, it is also inherently more flexible because you have complete deterministic control of how jogging behaves.
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 ***
 # Writing an Interface for Grbl
 _**FOR DEVELOPERS ONLY: This section outlines the recommended ways to setup a communications and streaming protocol with Grbl for a GUI.**_
 The general interface for Grbl has been described above, but what's missing is how to run an entire G-code program on Grbl, when it doesn't seem to have an upload feature. Or, how to build a decent GUI with real-time feedback. This is where this section fits in. Early on, users fiercely requested for flash drive, external RAM, LCD support, joysticks, or network support so they can upload a g-code program and run it directly on Grbl. The general answer to that is, good ideas, but Grbl doesn't need them. Grbl already has nearly all of the tools and features to reliably communicate with a simple graphical user interface (GUI). Plus, we want to minimize as much as we can on what Grbl should be doing, because, in the end, Grbl needs to be concentrating on producing clean, reliable motion. That's it.
 ## Streaming a G-Code Program to Grbl
 Here we will describe three different streaming methods for Grbl GUIs, but really there's only two that we recommend using. One of the main problems with streaming to Grbl is the USB port itself. Arduinos and most all micro controllers use a USB-to-serial converter chip that, at times, behaves strangely and not typically how you'd expect, like USB packet buffering and delays that can wreak havoc to a streaming protocol. Another problem is how to deal with some of the latency and oddities of the PCs themselves, because none of them are truly real-time and always create micro-delays when executing other tasks. Regardless, we've come up with ways to ensure the G-code stream is reliable and simple.
 #### Streaming Protocol: Simple Send-Response _[Recommended for Grbl v0.9+]_
 The send-response streaming protocol is the most fool-proof and simplest method to stream a G-code program to Grbl. The host PC interface simply sends a line of G-code to Grbl and waits for an `ok` or `error:` response before sending the next line of G-code. So, no matter if Grbl needs to wait for room in the look-ahead planner buffer to finish parsing and executing the last line of G-code or if the the host computer is busy doing something, this guarantees both to the host PC and Grbl, the programmed G-code has been sent and received properly. An example of this protocol is published in our `simple_stream.py` script in our repository.
 However, it's also the slowest of three outlined streaming protocols. Grbl essentially has two buffers between the execution of steps and the host PC interface. One of them is the serial receive buffer. This briefly stores up to 127 characters of data received from the host PC until Grbl has time to fetch and parse the line of G-code. The other buffer is the look-ahead planner buffer. This buffer stores up to 17 line motions that are acceleration-planned and optimized for step execution. Since the send-response protocol receives a line of G-code while the host PC waits for a response, Grbl's serial receive buffer is usually empty and under-utilized. If Grbl is actively running and executing steps, Grbl will immediately begin to execute and empty the look-ahead planner buffer, while it sends the response to the host PC, waits for the next line from the host PC, upon receiving it, parse and plan it, and add it to the end of the look-ahead buffer.
 Although this communication lag may take only a fraction of a second, there is a cumulative effect, because there is a lag with every G-code block sent to Grbl. In certain scenarios, like a G-code program containing lots of sequential, very short, line segments with high feed rates, the cumulative lag can be large enough to empty and starve the look-ahead planner buffer within this time. This could lead to start-stop motion when the streaming can't keep up with G-code program execution. Also, since Grbl can only plan and optimize what's in the look-ahead planner buffer, the performance through these types of motions will never be full-speed, because look-ahead buffer will always be partially full when using this streaming method. If your expected application doesn't contain a lot of these short line segments with high feed rates, this streaming protocol should be more than adequate for a vast majority of applications, is very robust, and is a quick way to get started. However, we do not recommend using this method for Grbl versions v0.8 or prior due to some performance issues with these versions.
 #### Streaming Protocol: Via Flow Control (XON/XOFF)
 To avoid the risk of starving the look-ahead planner buffer, a flow control streaming protocol can be used to try to keep Grbl's serial receive buffer full, so that Grbl has immediate access to the next g-code line to parse and plan without having to wait for the host PC to send it. Flow control, also known as XON/XOFF software flow control, uses two special characters to tell the host PC when it has or doesn't have room in the serial receive buffer to receive more data. When there is room, usually at 20% full, the special character is sent to the host PC indicating ready-to-receive. The host PC will begin to send data until it receives the other stop-receive special character, usually at 80% full. Grbl's XON/XOFF software flow control feature may be enabled through the config.h, but is not officially supported for the following reasons.
 While sound in logic, software flow control has a number of problems. The timing between Grbl and the host PC is almost never perfectly in sync, in large part due to the USB protocol and the USB-serial converter chips on every Arduino. This poses a big problem when sending and receiving these special flow-control characters. When Grbl's serial receive buffer is low, the time between when it sends the ready-to-receive character and when the host PC sends more data all depends everything in between. If the host PC is busy or the Arduino USB-serial converter is not sending the character on time, this lag can cause Grbl to wait for more serial data to come in before parsing and executing the next line of G-code. Even worse though, if the serial receive buffer is nearing full and the stop-receive character is sent, the host PC may not receive the signal in time to stop the data transfer and over-flow Grbl's serial buffer. This is bad and will corrupt the data stream.
 Because the software flow-control method is dependent on the performance of the USB-serial converter on the Arduino and the host PC, the low and high watermarks for the ready-to-receive and stop-receive characters must be tuned for each case. Thus, it's not really a robust solution. In our experience with XON/XOFF software flow control, it absolutely **DOES NOT** work with Arduinos with the Atmega8U/16U USB-serial converter chips (on all current Arduinos from the Uno to Mega2560). For some reason, there are USB packet delays that are out of Grbl's control and almost always led to data corruption. However, XON/XOFF worked, but only on older Arduinos or micro controllers that featured an FTDI RS232 USB-serial converter chip, such as the Duemilanove or controllers with an FTDI break-out board. The FTDI's firmware reliably sent the XON/XOFF special characters in time and on time. We're not sure why there is such a difference between them.
 If you decide to use XON/XOFF software flow control for your GUI, keep in mind that, at the moment, it'll only really works with FTDI USB-serial converters. But, the great thing about this method is that you can connect with Grbl over a serial emulator program like Coolterm, enable XON/XOFF flow control, cut-and-paste an entire g-code program into it, and Grbl will execute it completely. (Nice but not really necessary.)
 #### Streaming Protocol: Character-Counting _[**Recommended with Reservations**]_
 To get the best of both worlds, the simplicity and reliability of the send-response method and assurance of maximum performance with software flow control, we came up with a simple character-counting protocol for streaming a G-code program to Grbl. It works like the send-response method, where the host PC sends a line of G-code for Grbl to execute and waits for a response, but, rather than needing special XON/XOFF characters for flow control, this protocol simply uses Grbl's responses as a way to reliably track how much room there is in Grbl's serial receive buffer. An example of this protocol is outlined in the `stream.py` streaming script in our repo.
 The main difference between this protocol and the others is the host PC needs to maintain a standing count of how many characters it has sent to Grbl and then subtract the number of characters corresponding to the line executed with each Grbl response. Suppose there is a short G-code program that has 5 lines with 25, 40, 31, 58, and 20 characters (counting the line feed and carriage return characters too). We know Grbl has a 127 character serial receive buffer, and the host PC can send up to 127 characters without overflowing the buffer. If we let the host PC send as many complete lines as we can without over flowing Grbl's serial receive buffer, the first three lines of 25, 40, and 31 characters can be sent for a total of 96 characters. When Grbl responds, we know the first line has been processed and is no longer in the serial read buffer. As it stands, the serial read buffer now has the 40 and 31 character lines in it for a total of 71 characters. The host PC needs to then determine if it's safe to send the next line without overflowing the buffer. With the next line at 58 characters and the serial buffer at 71 for a total of 129 characters, the host PC will need to wait until more room has cleared from the serial buffer. When the next Grbl response comes in, the second line has been processed and only the third 31 character line remains in the serial buffer. At this point, it's safe to send the remaining last two 58 and 20 character lines of the g-code program for a total of 109.
 While seemingly complicated, this character-counting streaming protocol is extremely effective in practice. It always ensures Grbl's serial read buffer is filled, while never overflowing it. It maximizes Grbl's performance by keeping the look-ahead planner buffer full by better utilizing the bi-directional data flow of the serial port, and it's fairly simple to implement as our `stream.py` script illustrates. We have stress-tested this character-counting protocol to extremes and it has not yet failed. Seemingly, only the speed of the serial connection is the limit.
 _UPDATE: Up until recently, we've recommended that Grbl GUIs use this streaming protocol. It is indeed very efficient and effective, but there are a couple of additional things interface writers should aware of. These are issues being worked on for the v1.0 release._
 - _Since the GUI is preloading Grbl's serial RX buffer with commands, Grbl will continually execute all of the queued g-code in the RX serial buffer. The first problem is if there is an error at the beginning of the RX buffer, Grbl will continue to execute the remaining buffered g-code and the GUI won't be able to control what happens. The interim solution is to check all of the g-code via the $C check mode, so all errors are vetted prior to streaming._
 - _When Grbl stores data to EEPROM, the AVR requires all interrupts to be disabled during this write process, including the serial RX ISR. This means that if a g-code or Grbl `$` command writes to EEPROM, the data sent during the write may be lost. This is usually rare and typically occurs when streaming a G10 command inappropriately inside a program. For robustness, GUIs should track and detect these EEPROM write commands and handle them appropriately by waiting for the queue to finish executing before sending more data. Note that the simple send-response protocol doesn't not suffer from this issue._
 ## Interacting with Grbl's Systems
 Along with streaming a G-code program, there a few more things to consider when writing a GUI for Grbl, such as how to use status reporting, real-time control commands, dealing with EEPROM, and general message handling.
 #### Status Reporting
 When a `?` character is sent to Grbl (no additional line feed or carriage return character required), it will immediately respond with something like `<Idle,MPos:0.000,0.000,0.000,WPos:0.000,0.000,0.000>` to report its state and current position. The `?` is always picked-off and removed from the serial receive buffer whenever Grbl detects one. So, these can be sent at any time. Also, to make it a little easier for GUIs to pick up on status reports, they are always encased by `<>` chevrons.
 Developers can use this data to provide an on-screen position digital-read-out (DRO) for the user and/or to show the user a 3D position in a virtual workspace. We recommend querying Grbl for a `?` real-time status report at no more than 5Hz. 10Hz may be possible, but at some point, there are diminishing returns and you are taxing Grbl's CPU more by asking it to generate and send a lot of position data.
 Grbl's status report is fairly simply in organization. It always starts with a word describing the machine state like `IDLE` (descriptions of these are available elsewhere in the Wiki). The following data values are usually in the order listed below and separated by commas, but may not be in the exact order or printed at all. Report output depends on the user's `$10` status report mask setting.
 * `MPos:0.000,0.000,0.000` : Machine position listed as `X,Y,Z` coordinates. Units (mm or inch) depends on `$13` Grbl unit reporting setting.
 * `WPos:0.000,0.000,0.000` : Work position listed as `X,Y,Z` coordinates. Units (mm or inch) depends on `$13` Grbl unit reporting setting.
 * `Buf:0` : Number of motions queued in Grbl's planner buffer.
 * `RX:0` : Number of characters queued in Grbl's serial RX receive buffer.
 #### Real-Time Control Commands
 The real-time control commands, `~` cycle start/resume, `!` feed hold, and `^X` soft-reset, all immediately signal Grbl to change its running state. Just like `?` status reports, these control characters are picked-off and removed from the serial buffer when they are detected and do not require an additional line-feed or carriage-return character to operate.
 #### EEPROM Issues
 EEPROM access on the Arduino AVR CPUs turns off all of the interrupts while the CPU reads and writes to EEPROM. This poses a problem for certain features in Grbl, particularly if a user is streaming and running a g-code program, since it can pause the main step generator interrupt from executing on time. Most of the EEPROM access is restricted by Grbl when it's in certain states, but there are some things that developers need to know.
 * Settings can't be streamed to Grbl with either the XON/XOFF software flow control or the character-counting streaming protocols. Only the simple send-response protocol works. This is because during the EEPROM write, the AVR CPU also shuts-down the serial RX interrupt, which means data can get corrupted or lost. Note that the send-response protocol doesn't send any data until a response comes back.
 * When changing work coordinates, printing `$#` parameters, or accessing the `G28`/`G30` predefined positions, Grbl has to fetch them from EEPROM. There is a small chance this access can pause the stepper or serial receive interrupt long enough to cause motion issues, but since it only fetches 12 bytes at a time at 2 cycles per fetch, the chances are very small that this will do anything to how Grbl runs. We just suggest keeping an eye on this and report to us any issues you might think are related to this.
 For reference:
 * Grbl's EEPROM write commands: `G10 L2`, `G10 L20`, `G28.1`, `G30.1`, `$x=`, `$I=`, `$Nx=`, `$RST=`
 * Grbl's EEPROM read commands: `G54-G59`, `G28`, `G30`, `$$`, `$I`, `$N`, `$#`
 #### Message Handling
 Most of the feedback from Grbl fits into nice categories so GUIs can easily tell what is what. Here's how they are organized:
 * `ok`: Standard all-is-good response to a single line sent to Grbl.
 * `error:`: Standard error response to a single line sent to Grbl.
 * `ALARM:`: A critical error message that occurred. All processes stopped until user acknowledgment.
 * `[]`: All feedback messages are sent in brackets. These include parameter and g-code parser state print-outs.
 * `<>`: Status reports are sent in chevrons.
 There are few things that don't fit neatly into this setup at the moment. In the next version, we'll try to make this more universal, but for now, your GUIs will need to manually account for these:
 * The startup message.
 * `$` Help print-out.
 * `$N` Start-up blocks execution after the startup message.
 * The `$$` view Grbl settings print-out.
 #### G-code Error Handling
 As of Grbl v0.9, the g-code parser is fully standards-compilant with complete error-checking. When a G-code parser detects an error in a G-code block/line, the parser will dump everything in the block from memory and report an `error:` back to the user or GUI. This dump can pose problematic, because the bad G-code block may have contained some valuable positioning commands or feed rate settings.
 It's highly recommended to do what all professional CNC controllers do when they detect an error in the G-code program, _**halt**_. Don't do anything further until the user has modified the G-code and fixed the error in their program. Otherwise, bad things could happen.
 As a service to GUIs, Grbl has a "check G-code" mode, enabled by the `$C` system command. GUIs can stream a G-code program to Grbl, where it will parse it, error-check it, and report `ok`'s and `errors:`'s without powering on anything or moving. So GUIs can pre-check the programs before streaming them for real. To disable the "check G-code" mode, send another `$C` system command and Grbl will automatically soft-reset to flush and re-initialize the G-code parser and the rest of the system. This perhaps should be run in the background when a user first loads a program, before a user sets up his machine. This flushing and re-initialization clears `G92`'s by G-code standard, which some users still incorrectly use to set their part zero.
 #### Jogging
 Unfortunately, Grbl doesn't have a proper jogging interface, at least for now. This was to conserve precious flash space for the development of Grbl v0.9, but may be installed in the next release of Grbl. However, authors of Grbl GUIs have come up with ways to simulate jogging with Grbl by sending incremental motions, such as `G91 X0.1`, with each jogging click or key press. This works pretty well, but, if uncontrolled, a user can easily queue up more motions than they want without realizing it and move well-past their desired location.
 The general methodology that has been shown to work is to simply restrict the number of jogging commands sent to Grbl. This can be done by disabling key repeating when held down. The planner buffer queue size can be tracked such that only a handful of motions can be queued and executed.
 #### Synchronization
 For situations when a GUI needs to run a special set of commands for tool changes, auto-leveling, etc, there often needs to be a way to know when Grbl has completed a task and the planner buffer is empty. The absolute simplest way to do this is to insert a `G4 P0.01` dwell command, where P is in seconds and must be greater than 0.0. This acts as a quick force-synchronization and ensures the planner buffer is completely empty before the GUI sends the next task to execute.
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 ## Grbl v1.1 Realtime commands
 Realtime commands are single control characters that may be sent to Grbl to command and perform an action in real-time. This means that they can be sent at anytime, anywhere, and Grbl will immediately respond, regardless of what it is doing at the time. These commands include a reset, feed hold, resume, status report query, and overrides (in v1.1).
 A realtime command:
 - Will execute within tens of milliseconds.
 - Is a single character that may be sent to Grbl at any time.
 - Does not require a line feed or carriage return after them.
 - Is not considered a part of the streaming protocol. 
 - Are intercepted when they are received and never placed in a buffer to be parsed by Grbl.
 - Will ignore multiple commands until it has executed the first received command.
 - May be tied to an input pin and may be operated with a button or switch.
 - Actions depends on state or what Grbl is doing. It may not do anything.
 - Descriptions explain how they work and what to expect.
 #### ASCII Realtime Command Descriptions
 Four realtime commands are type-able by users on a keyboard and shown in the `$` Grbl help message. These realtime command characters control some of Grbl's basic functions.
 - `0x18` (ctrl-x) : Soft-Reset
  - Immediately halts and safely resets Grbl without a power-cycle.
  - Accepts and executes this command at any time.
  - If reset while in motion, Grbl will throw an alarm to indicate position may be lost from the motion halt.
  - If reset while in not motion, position is retained and re-homing is not required.
  - An input pin is available to connect a button or switch.
 - `?` : Status Report Query
  - Immediately generates and sends back runtime data with a status report.
  - Accepts and executes this command at any time, except during a homing cycle and when critical alarm (hard/soft limit error) is thrown.
 - `~` : Cycle Start / Resume
  - Resumes a feed hold, a safety door/parking state when the door is closed, and the M0 program pause states.
  - Command is otherwise ignored.
  - If the parking compile-time option is enabled and the safety door state is ready to resume, Grbl will re-enable the spindle and coolant, move back into position, and then resume.
  - An input pin is available to connect a button or switch.
 - `!` : Feed Hold
  - Places Grbl into a suspend or HOLD state. If in motion, the machine will decelerate to a stop and then be suspended.
  - Command executes when Grbl is in an IDLE, RUN, or JOG state. It is otherwise ignored.
  - If jogging, a feed hold will cancel the jog motion and flush all remaining jog motions in the planner buffer. The state will return from JOG to IDLE or DOOR, if was detected as ajar during the active hold.
  - By machine control definition, a feed hold does not disable the spindle or coolant. Only motion.
  - An input pin is available to connect a button or switch.
 #### Extended-ASCII Realtime Command Descriptions
 Grbl v1.1 installed more than a dozen new realtime commands to control feed, rapid, and spindle overrides. To help prevent users from inadvertently altering overrides with a keystroke and allow for more commands later on, all of the new control characters have been moved to the extended ASCII character set. These are not easily type-able on a keyboard, but, depending on the OS, they may be entered using specific keystroke and code. GUI developers will need to be able to send extended ASCII characters, values `128 (0x80)` to `255 (0xFF)`, to Grbl to take advantage of these new features.
 - `0x84` : Safety Door
  - Although typically connected to an input pin to detect the opening of a safety door, this command allows a GUI to enact the safety door behavior with this command.
  - Immediately suspends into a DOOR state and disables the spindle and coolant. If in motion, the machine will decelerate to a stop and then be suspended.
  - If executed during homing, Grbl will instead halt motion and throw a homing alarm.
  - If already in a suspend state or HOLD, the DOOR state supersedes it.
  - If the parking compile-time option is enabled, Grbl will park the spindle to a specified location.
  - Command executes when Grbl is in an IDLE, HOLD, RUN, HOMING, or JOG state. It is otherwise ignored.
  - If jogging, a safety door will cancel the jog and all queued motions in the planner buffer. When the safety door is closed and resumed, Grbl will return to an IDLE state.
  - An input pin is available to connect a button or switch, if enabled with a compile-time option.
  - Some builds of Grbl v0.9 used the `@` character for this command, but it was undocumented. Moved to extended-ASCII to prevent accidental commanding.
 - `0x85` : Jog Cancel
  - Immediately cancels the current jog state by a feed hold and automatically flushing any remaining jog commands in the buffer.
  - Command is ignored, if not in a JOG state or if jog cancel is already invoked and in-process.
  - Grbl will return to the IDLE state or the DOOR state, if the safety door was detected as ajar during the cancel.
 - Feed Overrides
  - Immediately alters the feed override value. An active feed motion is altered within tens of milliseconds.
  - Does not alter rapid rates, which include G0, G28, and G30, or jog motions.
  - Feed override value can not be 1% or greater than 200%
  - If feed override value does not change, the command is ignored.
  - Feed override range and increments may be changed in config.h.
  - The commands are:
    - `0x90` : Set 100% of programmed rate.
    - `0x91` : Increase 10%
    - `0x92` : Decrease 10%
    - `0x93` : Increase 1%
    - `0x94` : Decrease 1%
 - Rapid Overrides
  - Immediately alters the rapid override value. An active rapid motion is altered within tens of milliseconds.
  - Only effects rapid motions, which include G0, G28, and G30.
  - If rapid override value does not change, the command is ignored.
  - Rapid override set values may be changed in config.h.
  - The commands are:
    - `0x95` : Set to 100% full rapid rate.
    - `0x96` : Set to 50% of rapid rate.
    - `0x97` : Set to 25% of rapid rate.
 - Spindle Speed Overrides
  - Immediately alters the spindle speed override value. An active spindle speed is altered within tens of milliseconds.
  - Override values may be changed at any time, regardless of if the spindle is enabled or disabled.
  - Spindle override value can not be 50% or greater than 200%
  - If spindle override value does not change, the command is ignored.
  - Spindle override range and increments may be altered in config.h.
  - The commands are:
    - `0x99` : Set 100% of programmed spindle speed
    - `0x9A` : Increase 10%
    - `0x9B` : Decrease 10%
    - `0x9C` : Increase 1%
    - `0x9D` : Decrease 1%
 - `0x9E` : Toggle Spindle Stop
  - Toggles spindle enable or disable state immediately, but only while in the HOLD state.
  - The command is otherwise ignored, especially while in motion. This prevents accidental disabling during a job that can either destroy the part/machine or cause personal injury. Industrial machines handle the spindle stop override similarly.
  - When motion restarts via cycle start, the last spindle state will be restored and wait 4.0 seconds (configurable) before resuming the tool path. This ensures the user doesn't forget to turn it back on.
  - While disabled, spindle speed override values may still be altered and will be in effect once the spindle is re-enabled.
  - If a safety door is opened, the DOOR state will supersede the spindle stop override, where it will manage the spindle re-energizing itself upon closing the door and resuming. The prior spindle stop override state is cleared and reset.
 - `0xA0` : Toggle Flood Coolant
  - Toggles flood coolant state and output pin until the next toggle or g-code command alters it.
  - May be commanded at any time while in IDLE, RUN, or HOLD states. It is otherwise ignored.
  - This override directly changes the coolant modal state in the g-code parser. Grbl will continue to operate normally like it received and executed an `M8` or `M9` g-code command.
  - When `$G` g-code parser state is queried, the toggle override change will be reflected by an `M8` enabled or disabled with an `M9` or not appearing when `M7` is present.
 - `0xA1` : Toggle Mist Coolant
  - Enabled by `ENABLE_M7` compile-time option. Default is disabled.
  - Toggles mist coolant state and output pin until the next toggle or g-code command alters it.
  - May be commanded at any time while in IDLE, RUN, or HOLD states. It is otherwise ignored.
  - This override directly changes the coolant modal state in the g-code parser. Grbl will continue to operate normally like it received and executed an `M7` or `M9` g-code command.
  - When `$G` g-code parser state is queried, the toggle override change will be reflected by an `M7` enabled or disabled with an `M9` or not appearing when `M8` is present.
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 #### _Quick-Links:_
 * [Getting Started](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9#getting-started)
 * [Grbl Settings](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9#grbl-settings)
 * [Grbl's Settings and What They Mean](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9#grbls-xval-settings-and-what-they-mean)
 * [Grbl's Other `$` Commands](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9#grbls-other--commands)
 * [Real-Time Commands](https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9#real-time-commands----and-ctrl-x)
 ***
 ## Getting Started
 First, connect to Grbl using the serial terminal of your choice.
 Set the baud rate  to **115200** as 8-N-1 (8-bits, no parity, and 1-stop bit.)
 Once connected
 you should get the Grbl-prompt, which looks like this:
 ```
 Grbl 1.1c ['$' for help]
 ```
 Type $ and press enter to have Grbl print a help message. You should not see any local echo of the $ and enter. Grbl should respond with:
 ```
 [HLP:$$ $# $G $I $N $x=val $Nx=line $J=line $SLP $C $X $H ~ ! ? ctrl-x]
 ```
 The ‘$’-commands are Grbl system commands used to tweak the settings, view or change Grbl's states and running modes, and start a homing cycle. The last four **non**-'$' commands are realtime control commands that can be sent at anytime, no matter what Grbl is doing. These either immediately change Grbl's running behavior or immediately print a report of the important realtime data like current position (aka DRO).
 ***
 ##Grbl Settings
 #### $$ - View Grbl settings
 To view the settings, type `$$` and press enter after connecting to Grbl. Grbl should respond with a list of the current system settings, as shown in the example below. All of these settings are persistent and kept in EEPROM, so if you power down, these will be loaded back up the next time you power up your Arduino.
 The `x` of `$x=val` indicates a particular setting, while `val` is the setting value. In prior versions of Grbl, each setting had a description next to it in `()` parentheses, but Grbl v1.1+ no longer includes them unfortunately. This was done to free up precious flash memory to add the new features available in v1.1. However, most good GUIs will help out by attaching descriptions for you, so you know what you are looking at.
 ```
 $0=10
 $1=25
 $2=0
 $3=0
 $4=0
 $5=0
 $6=0
 $10=1
 $11=0.010
 $12=0.002
 $13=0
 $20=0
 $21=0
 $22=1
 $23=0
 $24=25.000
 $25=500.000
 $26=250
 $27=1.000
 $30=1000.
 $31=0.
 $32=0
 $100=250.000
 $101=250.000
 $102=250.000
 $110=500.000
 $111=500.000
 $112=500.000
 $120=10.000
 $121=10.000
 $122=10.000
 $130=200.000
 $131=200.000
 $132=200.000
 ```
 #### $x=val - Save Grbl setting
 The `$x=val` command saves or alters a Grbl setting, which can be done manually by sending this command when connected to Grbl through a serial terminal program, but most Grbl GUIs will do this for you as a user-friendly feature.
 To manually change e.g. the microseconds step pulse option to 10us you would type this, followed by an enter:
 ```
 $0=10
 ```
 If everything went well, Grbl will respond with an 'ok' and this setting is stored in EEPROM and will be retained forever or until you change them. You can check if Grbl has received and stored your setting correctly by typing `$$` to view the system settings again.
 ***
 ## Grbl's `$x=val` settings and what they mean
 **NOTE: From Grbl v0.9 to Grbl v1.1, only `$10` status reports changed and new `$30`/ `$31` spindle rpm max/min and `$32` laser mode settings were added. Everything else is the same.**
 #### $0 – Step pulse, microseconds
 Stepper drivers are rated for a certain minimum step pulse length. Check the data sheet or just try some numbers. You want the shortest pulses the stepper drivers can reliably recognize. If the pulses are too long, you might run into trouble when running the system at very high feed and pulse rates, because the step pulses can begin to overlap each other. We recommend something around 10 microseconds, which is the default value.
 #### $1 - Step idle delay, milliseconds
 Every time your steppers complete a motion and come to a stop, Grbl will delay disabling the steppers by this value. **OR**, you can always keep your axes enabled (powered so as to hold position) by setting this value to the maximum 255 milliseconds. Again, just to repeat, you can keep all axes always enabled by setting `$1=255`.
 The stepper idle lock time is the time length Grbl will keep the steppers locked before disabling. Depending on the system, you can set this to zero and disable it. On others, you may need 25-50 milliseconds to make sure your axes come to a complete stop before disabling. This is to help account for machine motors that do not like to be left on for long periods of time without doing something. Also, keep in mind that some stepper drivers don't remember which micro step they stopped on, so when you re-enable, you may witness some 'lost' steps due to this. In this case, just keep your steppers enabled via `$1=255`.
 #### $2 – Step port invert, mask
 This setting inverts the step pulse signal. By default, a step signal starts at normal-low and goes high upon a step pulse event. After a step pulse time set by `$0`, the pin resets to low, until the next step pulse event. When inverted, the step pulse behavior switches from normal-high, to low during the pulse, and back to high. Most users will not need to use this setting, but this can be useful for certain CNC-stepper drivers that have peculiar requirements. For example, an artificial delay between the direction pin and step pulse can be created by inverting the step pin.
 This invert mask setting is a value which stores the axes to invert as bit flags. You really don't need to completely understand how it works. You simply need to enter the settings value for the axes you want to invert. For example, if you want to invert the X and Z axes, you'd send `$2=5` to Grbl and the setting should now read `$2=5 (step port invert mask:00000101)`.
 | Setting Value | Mask |Invert X | Invert Y | Invert Z |
 |:-------------:|:----:|:-------:|:--------:|:--------:|
 | 0 | 00000000 |N | N | N |
 | 1 | 00000001 |Y | N | N |
 | 2 | 00000010 |N | Y | N |
 | 3 | 00000011 |Y | Y | N |
 | 4 | 00000100 |N | N | Y |
 | 5 | 00000101 |Y | N | Y |
 | 6 | 00000110 |N | Y | Y |
 | 7 | 00000111 |Y | Y | Y |
 #### $3 – Direction port invert, mask
 This setting inverts the direction signal for each axis. By default, Grbl assumes that the axes move in a positive direction when the direction pin signal is low, and a negative direction when the pin is high. Often, axes don't move this way with some machines. This setting will invert the direction pin signal for those axes that move the opposite way.
 This invert mask setting works exactly like the step port invert mask and stores which axes to invert as bit flags. To configure this setting, you simply need to send the value for the axes you want to invert. Use the table above. For example, if want to invert the Y axis direction only, you'd send `$3=2` to Grbl and the setting should now read `$3=2 (dir port invert mask:00000010)`
 #### $4 - Step enable invert, boolean
 By default, the stepper enable pin is high to disable and low to enable. If your setup needs the opposite, just invert the stepper enable pin by typing `$4=1`. Disable with `$4=0`. (May need a power cycle to load the change.)
 #### $5 -  Limit pins invert, boolean
 By default, the limit pins are held normally-high with the Arduino's internal pull-up resistor. When a limit pin is low, Grbl interprets this as triggered. For the opposite behavior, just invert the limit pins by typing `$5=1`. Disable with `$5=0`. You may need a power cycle to load the change.
 NOTE: If you invert your limit pins, you will need an external pull-down resistor wired in to all of the limit pins to prevent overloading the pins with current and frying them.
 #### $6 -  Probe pin invert, boolean
 By default, the probe pin is held normally-high with the Arduino's internal pull-up resistor. When the probe pin is low, Grbl interprets this as triggered. For the opposite behavior, just invert the probe pin by typing `$6=1`. Disable with `$6=0`. You may need a power cycle to load the change.
 NOTE: If you invert your probe pin, you will need an external pull-down resistor wired in to the probe pin to prevent overloading it with current and frying it.
 #### $10 - Status report, mask
 This setting determines what Grbl real-time data it reports back to the user when a '?' status report is sent. This data includes current run state, real-time position, real-time feed rate, pin states, current override values, buffer states, and the g-code line number currently executing (if enabled through compile-time options).
 By default, the new report implementation in Grbl v1.1+ will include just about everything in the standard status report. A lot of the data is hidden and will appear only if it changes. This increases efficiency dramatically over of the old report style and allows you to get faster updates and still get more data about your machine. The interface documentation outlines how it works and most of it applies only to GUI developers or the curious.
 To keep things simple and consistent, Grbl v1.1 has only two reporting options. These are primarily here just for users and developers to help set things up. 
 - Position type may be specified to show either machine position (`MPos:`)  or work position (`WPos:`), but no longer both at the same time. Enabling work position is useful in certain scenarios when Grbl is being directly interacted with through a serial terminal, but _machine position reporting should be used by default._ 
 - Usage data of Grbl's planner and serial RX buffers may be enabled. This shows the number of blocks or bytes available in the respective buffers. This is generally used to helps determine how Grbl is performing when testing out a streaming interface. _This should be disabled by default._
 Use the table below enables and disable reporting options. Simply add the values listed of what you'd like to enable, then save it by sending Grbl your setting value. For example, the default report with machine position and no buffer data reports setting is `$10=1`. If work position and buffer data are desired, the setting will be `$10=2`.
 | Report Type | Value | Description |
 |:-------------:|:----:|:----:|
 | Position Type | 1 | Enabled `MPos:`. Disabled `WPos:`. |
 | Buffer Data | 2 | Enabled `Buf:` field appears with planner and serial RX available buffer.
 #### $11 - Junction deviation, mm
 Junction deviation is used by the acceleration manager to determine how fast it can move through line segment junctions of a G-code program path. For example, if the G-code path has a sharp 10 degree turn coming up and the machine is moving at full speed, this setting helps determine how much the machine needs to slow down to safely go through the corner without losing steps.
 How we calculate it is a bit complicated, but, in general, higher values gives faster motion through corners, while increasing the risk of losing steps and positioning. Lower values makes the acceleration manager more careful and will lead to careful and slower cornering. So if you run into problems where your machine tries to take a corner too fast, *decrease* this value to make it slow down when entering corners. If you want your machine to move faster through junctions, *increase* this value to speed it up. For curious people, hit this [link](http://t.co/KQ5BvueY) to read about Grbl's cornering algorithm, which accounts for both velocity and junction angle with a very simple, efficient, and robust method.
 #### $12 – Arc tolerance, mm
 Grbl renders G2/G3 circles, arcs, and helices by subdividing them into teeny tiny lines, such that the arc tracing accuracy is never below this value. You will probably never need to adjust this setting, since `0.002mm` is well below the accuracy of most all CNC machines. But if you find that your circles are too crude or arc tracing is performing slowly, adjust this setting. Lower values give higher precision but may lead to performance issues by overloading Grbl with too many tiny lines. Alternately, higher values traces to a lower precision, but can speed up arc performance since Grbl has fewer lines to deal with.
 For the curious, arc tolerance is defined as the maximum perpendicular distance from a line segment with its end points lying on the arc, aka a chord. With some basic geometry, we solve for the length of the line segments to trace the arc that satisfies this setting. Modeling arcs in this way is great, because the arc line segments automatically adjust and scale with length to ensure optimum arc tracing performance, while never losing accuracy.
 #### $13 - Report inches, boolean
 Grbl has a real-time positioning reporting feature to provide a user feedback on where the machine is exactly at that time, as well as, parameters for coordinate offsets and probing. By default, it is set to report in mm, but by sending a `$13=1` command, you send this boolean flag to true and these reporting features will now report in inches. `$13=0` to set back to mm.
 #### $20 - Soft limits, boolean
 Soft limits is a safety feature to help prevent your machine from traveling too far and beyond the limits of travel, crashing or breaking something expensive. It works by knowing the maximum travel limits for each axis and where Grbl is in machine coordinates. Whenever a new G-code motion is sent to Grbl, it checks whether or not you accidentally have exceeded your machine space. If you do, Grbl will issue an immediate feed hold wherever it is, shutdown the spindle and coolant, and then set the system alarm indicating the problem. Machine position will be retained afterwards, since it's not due to an immediate forced stop like hard limits.
 NOTE: Soft limits requires homing to be enabled and accurate axis maximum travel settings, because Grbl needs to know where it is. `$20=1` to enable, and `$20=0` to disable.
 #### $21 - Hard limits, boolean
 Hard limit work basically the same as soft limits, but use physical switches instead. Basically you wire up some switches (mechanical, magnetic, or optical) near the end of travel of each axes, or where ever you feel that there might be trouble if your program moves too far to where it shouldn't. When the switch triggers, it will immediately halt all motion, shutdown the coolant and spindle (if connected), and go into alarm mode, which forces you to check your machine and reset everything.
 To use hard limits with Grbl, the limit pins are held high with an internal pull-up resistor, so all you have to do is wire in a normally-open switch with the pin and ground and enable hard limits with `$21=1`. (Disable with `$21=0`.) We strongly advise taking electric interference prevention measures. If you want a limit for both ends of travel of one axes, just wire in two switches in parallel with the pin and ground, so if either one of them trips, it triggers the hard limit.
 Keep in mind, that a hard limit event is considered to be critical event, where steppers immediately stop and will have likely have lost steps. Grbl doesn't have any feedback on position, so it can't guarantee it has any idea where it is. So, if a hard limit is triggered, Grbl will go into an infinite loop ALARM mode, giving you a chance to check your machine and forcing you to reset Grbl. Remember it's a purely a safety feature.
 #### $22 - Homing cycle, boolean
 Ahh, homing. For those just initiated into CNC, the homing cycle is used to accurately and precisely locate a known and consistent position on a machine every time you start up your Grbl between sessions. In other words, you know exactly where you are at any given time, every time. Say you start machining something or are about to start the next step in a job and the power goes out, you re-start Grbl and Grbl has no idea where it is. You're left with the task of figuring out where you are. If you have homing, you always have the machine zero reference point to locate from, so all you have to do is run the homing cycle and resume where you left off.
 To set up the homing cycle for Grbl, you need to have limit switches in a fixed position that won't get bumped or moved, or else your reference point gets messed up. Usually they are setup in the farthest point in +x, +y, +z of each axes. Wire your limit switches in with the limit pins and ground, just like with the hard limits, and enable homing. If you're curious, you can use your limit switches for both hard limits AND homing. They play nice with each other.
 By default, Grbl's homing cycle moves the Z-axis positive first to clear the workspace and then moves both the X and Y-axes at the same time in the positive direction. To set up how your homing cycle behaves, there are more Grbl settings down the page describing what they do (and compile-time options as well.)
 Also, one more thing to note, when homing is enabled. Grbl will lock out all G-code commands until you perform a homing cycle. Meaning no axes motions, unless the lock is disabled ($X) but more on that later. Most, if not all CNC controllers, do something similar, as it is mostly a safety feature to prevent users from making a positioning mistake, which is very easy to do and be saddened when a mistake ruins a part. If you find this annoying or find any weird bugs, please let us know and we'll try to work on it so everyone is happy. :)
 NOTE: Check out config.h for more homing options for advanced users. You can disable the homing lockout at startup, configure which axes move first during a homing cycle and in what order, and more.
 #### $23 - Homing dir invert, mask
 By default, Grbl assumes your homing limit switches are in the positive direction, first moving the z-axis positive, then the x-y axes positive before trying to precisely locate machine zero by going back and forth slowly around the switch. If your machine has a limit switch in the negative direction, the homing direction mask can invert the axes' direction. It works just like the step port invert and direction port invert masks, where all you have to do is send the value in the table to indicate what axes you want to invert and search for in the opposite direction.
 #### $24 - Homing feed, mm/min
 The homing cycle first searches for the limit switches at a higher seek rate, and after it finds them, it moves at a slower feed rate to home into the precise location of machine zero. Homing feed rate is that slower feed rate. Set this to whatever rate value that provides repeatable and precise machine zero locating.
 #### $25 - Homing seek, mm/min
 Homing seek rate is the homing cycle search rate, or the rate at which it first tries to find the limit switches. Adjust to whatever rate gets to the limit switches in a short enough time without crashing into your limit switches if they come in too fast.
 #### $26 - Homing debounce, milliseconds
 Whenever a switch triggers, some of them can have electrical/mechanical noise that actually 'bounce' the signal high and low for a few milliseconds before settling in. To solve this, you need to debounce the signal, either by hardware with some kind of signal conditioner or by software with a short delay to let the signal finish bouncing. Grbl performs a short delay, only homing when locating machine zero. Set this delay value to whatever your switch needs to get repeatable homing. In most cases, 5-25 milliseconds is fine.
 #### $27 - Homing pull-off, mm
 To play nice with the hard limits feature, where homing can share the same limit switches, the homing cycle will move off all of the limit switches by this pull-off travel after it completes. In other words, it helps to prevent accidental triggering of the hard limit after a homing cycle.
 #### $30 - Max spindle speed, RPM
 This sets the spindle speed for the maximum 5V PWM pin output. Higher programmed spindle RPMs are accepted by Grbl but the PWM output will not exceed the max 5V. By default, Grbl linearly relates the max-min RPMs to 5V-0.02V PWM pin output in 255 increments. When the PWM pin reads 0V, this indicates spindle disabled. Note that there are additional configuration options are available in config.h to tweak how this operates.
 #### $31 - Min spindle speed, RPM
 This sets the spindle speed for the minimum 0.02V PWM pin output (0V is disabled).  Lower RPM values are accepted by Grbl but the PWM output will not go below 0.02V, except when RPM is zero. If zero, the spindle is disabled and PWM output is 0V. 
 #### $32 - Laser mode, boolean
 When enabled, Grbl will move continuously through consecutive `G1`, `G2`, or `G3` motion commands when programmed with a `S` spindle speed (laser power). The spindle PWM pin will be updated instantaneously through each motion without stopping. However, Grbl will still stop motion if a spindle state is commanded and altered, like `M3`, `M4`, or `M5`. If the spindle needs to be disabled while under continuous motion, program a `S0`, zero spindle speed, to disable the spindle with a supported motion command.
 When disabled, Grbl will operate as it always has, stopping motion with every `S` spindle speed command. This is the normal operating
 #### $100, $101 and $102 – [X,Y,Z] steps/mm
 Grbl needs to know how far each step will take the tool in reality. To calculate steps/mm for an axis of your machine you need to know:
 * The mm traveled per revolution of your stepper motor. This is dependent on your belt drive gears or lead screw pitch.
 * The full steps per revolution of your steppers (typically 200)
 * The microsteps per step of your controller (typically 1, 2, 4, 8, or 16). _Tip: Using high microstep values (e.g., 16) can reduce your stepper motor torque, so use the lowest that gives you the desired axis resolution and comfortable running properties._
 The steps/mm can then be calculated like this: ```steps_per_mm = (steps_per_revolution*microsteps)/mm_per_rev```
 Compute this value for every axis and write these settings to Grbl.
 #### $110, $111 and $112 – [X,Y,Z] Max rate, mm/min
 This sets the maximum rate each axis can move. Whenever Grbl plans a move, it checks whether or not the move causes any one of these individual axes to exceed their max rate. If so, it'll slow down the motion to ensure none of the axes exceed their max rate limits. This means that each axis has its own independent speed, which is extremely useful for limiting the typically slower Z-axis.
 The simplest way to determine these values is to test each axis one at a time by slowly increasing max rate settings and moving it. For example, to test the X-axis, send Grbl something like `G0 X50` with enough travel distance so that the axis accelerates to its max speed. You'll know you've hit the max rate threshold when your steppers stall. It'll make a bit of noise, but shouldn't hurt your motors. Enter a setting a 10-20% below this value, so you can account for wear, friction, and the mass of your workpiece/tool. Then, repeat for your other axes.
 NOTE: This max rate setting also sets the G0 seek rates.
 #### $120, $121, $122 – [X,Y,Z] Acceleration, mm/sec^2
 This sets the axes acceleration parameters in mm/second/second. Simplistically, a lower value makes Grbl ease slower into motion, while a higher value yields tighter moves and reaches the desired feed rates much quicker. Much like the max rate setting, each axis has its own acceleration value and are independent of each other. This means that a multi-axis motion will only accelerate as quickly as the lowest contributing axis can.
 Again, like the max rate setting, the simplest way to determine the values for this setting is to individually test each axis with slowly increasing values until the motor stalls. Then finalize your acceleration setting with a value 10-20% below this absolute max value. This should account for wear, friction, and mass inertia. We highly recommend that you dry test some G-code programs with your new settings before committing to them. Sometimes the loading on your machine is different when moving in all axes together.
 #### $130, $131, $132 – [X,Y,Z] Max travel, mm
 This sets the maximum travel from end to end for each axis in mm. This is only useful if you have soft limits (and homing) enabled, as this is only used by Grbl's soft limit feature to check if you have exceeded your machine limits with a motion command.
 ***
 ## Grbl's Other '$' Commands
 The other `$` commands provide additional controls for the user, such as printing feedback on the current G-code parser modal state or running the homing cycle. This section explains what these commands are and how to use them.
 #### `$#` - View gcode parameters
 G-code parameters store the coordinate offset values for G54-G59 work coordinates, G28/G30 pre-defined positions, G92 coordinate offset, tool length offsets, and probing (not officially, but we added here anyway). Most of these parameters are directly written to EEPROM anytime they are changed and are persistent. Meaning that they will remain the same, regardless of power-down, until they are explicitly changed. The non-persistent parameters, which will are not retained when reset or power-cycled, are G92, G43.1 tool length offsets, and the G38.2 probing data.
 G54-G59 work coordinates can be changed via the `G10 L2 Px` or `G10 L20 Px` command defined by the NIST gcode standard and the EMC2 (linuxcnc.org) standard. G28/G30 pre-defined positions can be changed via the `G28.1` and the `G30.1` commands, respectively.
 When `$#` is called, Grbl will respond with the stored offsets from machine coordinates for each system as follows. `TLO` denotes tool length offset (for the default z-axis), and `PRB` denotes the coordinates of the last probing cycle, where the suffix `:1` denotes if the last probe was successful and `:0` as not successful.
 ```
 [G54:4.000,0.000,0.000]
 [G55:4.000,6.000,7.000]
 [G56:0.000,0.000,0.000]
 [G57:0.000,0.000,0.000]
 [G58:0.000,0.000,0.000]
 [G59:0.000,0.000,0.000]
 [G28:1.000,2.000,0.000]
 [G30:4.000,6.000,0.000]
 [G92:0.000,0.000,0.000]
 [TLO:0.000]
 [PRB:0.000,0.000,0.000:0]
 ```
 #### `$G` - View gcode parser state
 This command prints all of the active gcode modes in Grbl's G-code parser. When sending this command to Grbl, it will reply with a message starting with an `[GC:` indicator like: 
 ```
 [GC:G0 G54 G17 G21 G90 G94 M0 M5 M9 T0 S0.0 F500.0]
 ```
 These active modes determine how the next G-code block or command will be interpreted by Grbl's G-code parser. For those new to G-code and CNC machining, modes sets the parser into a particular state so you don't have to constantly tell the parser how to parse it. These modes are organized into sets called "modal groups" that cannot be logically active at the same time. For example, the units modal group sets whether your G-code program is interpreted in inches or in millimeters.
 A short list of the modal groups, supported by Grbl, is shown below, but more complete and detailed descriptions can be found at LinuxCNC's [website](http://www.linuxcnc.org/docs/2.4/html/gcode_overview.html#sec:Modal-Groups). The G-code commands in **bold** indicate the default modes upon powering-up Grbl or resetting it.
 | Modal Group Meaning	|  Member Words |
 |:----:|:----:|
 | Motion Mode | **G0**, G1, G2, G3, G38.2, G38.3, G38.4, G38.5, G80 |
 |Coordinate System Select	| **G54**, G55, G56, G57, G58, G59|
 |Plane Select	| **G17**, G18, G19|
 |Distance Mode	| **G90**, G91|
 |Arc IJK Distance Mode | **G91.1** |
 |Feed Rate Mode	| G93, **G94**|
 |Units Mode	| G20, **G21**|
 |Cutter Radius Compensation | **G40** |
 |Tool Length Offset |G43.1, **G49**|
 |Program Mode | **M0**, M1, M2, M30|
 |Spindle State |M3, M4, **M5**|
 |Coolant State	| M7, M8, **M9** |
 In addition to the G-code parser modes, Grbl will report the active `T` tool number, `S` spindle speed, and `F` feed rate, which all default to 0 upon a reset. For those that are curious, these don't quite fit into nice modal groups, but are just as important for determining the parser state.
 #### `$I` - View build info
 This prints feedback to the user the Grbl version and source code build date. Optionally, `$I` can also store a short string to help identify which CNC machine you are communicating with, if you have more than machine using Grbl. To set this string, send Grbl `$I=xxx`, where `xxx` is your customization string that is less than 80 characters. The next time you query Grbl with a `$I` view build info, Grbl will print this string after the version and build date.
 NOTE: Some OEMs may block access to over-writing the build info string so they can store product information and codes there.
 #### $N - View startup blocks
 `$Nx` are the startup blocks that Grbl runs every time you power on Grbl or reset Grbl. In other words, a startup block is a line of G-code that you can have Grbl auto-magically run to set your G-code modal defaults, or anything else you need Grbl to do everytime you start up your machine. Grbl can store two blocks of G-code as a system default.
 So, when connected to Grbl, type `$N` and then enter. Grbl should respond with something short like:
 ```
 $N0=
 $N1=
 ok
 ```
 Not much to go on, but this just means that there is no G-code block stored in line `$N0` for Grbl to run upon startup. `$N1` is the next line to be run.
 #### $Nx=line - Save startup block
 **IMPORTANT: Be very careful when storing any motion (G0/1,G2/3,G28/30) commands in the startup blocks. These motion commands will run everytime you reset or power up Grbl, so if you have an emergency situation and have to e-stop and reset, a startup block move can and will likely make things worse quickly. Also, do not place any commands that save data to EEPROM, such as G10/G28.1/G30.1. This will cause Grbl to constantly re-write this data upon every startup and reset, which will eventually wear out your Arduino's EEPROM.**
 **Typical usage for a startup block is simply to set your preferred modal states, such as G20 inches mode, always default to a different work coordinate system, or, to provide a way for a user to run some user-written unique feature that they need for their crazy project.**
 To set a startup block, type `$N0=` followed by a valid G-code block and an enter. Grbl will run the block to check if it's valid and then reply with an `ok` or an `error:` to tell you if it's successful or something went wrong. If there is an error, Grbl will not save it.
 For example, say that you want to use your first startup block `$N0` to set your G-code parser modes like G54 work coordinate, G20 inches mode, G17 XY-plane. You would type `$N0=G20 G54 G17` with an enter and you should see an `ok` response. You can then check if it got stored by typing `$N` and you should now see a response like `$N0=G20G54G17`.
 Once you have a startup block stored in Grbl's EEPROM, everytime you startup or reset you will see your startup block printed back to you, starting with an open-chevron `>`, and a `:ok` response from Grbl to indicate if it ran okay. So for the previous example, you'll see:
 ```
 Grbl 1.1c ['$' for help]
 >G20G54G17:ok
 ```
 If you have multiple G-code startup blocks, they will print back to you in order upon every startup. And if you'd like to clear one of the startup blocks, (e.g., block 0) type `$N0=` without anything following the equal sign.
 NOTE: There are two variations on when startup blocks with run. First, it will not run if Grbl initializes up in an ALARM state or exits an ALARM state via an `$X` unlock for safety reasons. Always address and cancel the ALARM and then finish by a reset, where the startup blocks will run at initialization. Second, if you have homing enabled, the startup blocks will execute immediately after a successful homing cycle, not at startup.
 #### `$C` - Check gcode mode
 This toggles the Grbl's gcode parser to take all incoming blocks and process them completely, as it would in normal operation, but it does not move any of the axes, ignores dwells, and powers off the spindle and coolant. This is intended as a way to provide the user a way to check how their new G-code program fares with Grbl's parser and monitor for any errors (and checks for soft limit violations, if enabled).
 When toggled off, Grbl will perform an automatic soft-reset (^X). This is for two purposes. It simplifies the code management a bit. But, it also prevents users from starting a job when their G-code modes are not what they think they are. A system reset always gives the user a fresh, consistent start.
 #### `$X` - Kill alarm lock
 Grbl's alarm mode is a state when something has gone critically wrong, such as a hard limit or an abort during a cycle, or if Grbl doesn't know its position. By default, if you have homing enabled and power-up the Arduino, Grbl enters the alarm state, because it does not know its position. The alarm mode will lock all G-code commands until the '$H' homing cycle has been performed. Or if a user needs to override the alarm lock to move their axes off their limit switches, for example, '$X' kill alarm lock will override the locks and allow G-code functions to work again.
 But, tread carefully!! This should only be used in emergency situations. The position has likely been lost, and Grbl may not be where you think it is. So, it's advised to use G91 incremental mode to make short moves. Then, perform a homing cycle or reset immediately afterwards.
 As noted earlier, startup lines do not execute after a `$X` command. Always reset when you have cleared the alarm and fixed the scenario that caused it. When Grbl resets to idle, the startup lines will then run as normal.
 #### `$H` - Run homing cycle
 This command is the only way to perform the homing cycle in Grbl. Some other motion controllers designate a special G-code command to run a homing cycle, but this is incorrect according to the G-code standards. Homing is a completely separate command handled by the controller.
 TIP: After running a homing cycle, rather jogging manually all the time to a position in the middle of your workspace volume. You can set a G28 or G30 pre-defined position to be your post-homing position, closer to where you'll be machining. To set these, you'll first need to jog your machine to where you would want it to move to after homing. Type G28.1 (or G30.1) to have Grbl store that position. So then after '$H' homing, you could just enter 'G28' (or 'G30') and it'll move there auto-magically. In general, I would just move the XY axis to the center and leave the Z-axis up. This ensures that there isn't a chance the tool in the spindle will interfere and that it doesn't catch on anything.
 #### `$Jx=line` - Run jogging motion
 New to Grbl v1.1, this command will execute a special jogging motion. There are three main differences between a jogging motion and a motion commanded by a g-code line. 
 - Like normal g-code commands, several jog motions may be queued into the planner buffer, but the jogging can be easily canceled by a jog-cancel or feed-hold real-time command. Grbl will immediately hold the current jog and then automatically purge the buffers of any remaining commands. 
 - Jog commands are completely independent of the g-code parser state. It will not change any modes like `G91` incremental distance mode. So, you no longer have to make sure that you change it back to `G90` absolute distance mode afterwards. This helps reduce the chance of starting with the wrong g-code modes enabled.
 - If soft-limits are enabled, any jog command that exceeds a soft-limit will simply return an error. It will not throw an alarm as it would with a normal g-code command. This allows for a much more enjoyable and fluid GUI or joystick interaction.
 Executing a jog requires a specific command structure, as described below:
 - The first three characters must be '$J=' to indicate the jog.
 - The jog command follows immediate after the '=' and works like a normal G1 command.
 - Feed rate is only interpreted in G94 units per minute. A prior G93 state is ignored during jog.
 - Required words:
   - XYZ: One or more axis words with target value.
   - F - Feed rate value. NOTE: Each jog requires this value and is not treated as modal.
 - Optional words: Jog executes based on current G20/G21 and G90/G91 g-code parser state. If one of the following optional words is passed, that state is overridden for one command only.
   - G20 or G21 - Inch and millimeter mode
   - G90 or G91 - Absolute and incremental distances
   - G53 - Move in machine coordinates
 - All other g-codes, m-codes, and value words are not accepted in the jog command.
 - Spaces and comments are allowed in the command. These are removed by the pre-parser.
 - Example: G21 and G90 are active modal states prior to jogging. These are sequential commands.
    - `$J=X10.0 Y-1.5` will move to X=10.0mm and Y=-1.5mm in work coordinate frame (WPos).
    - `$J=G91 G20 X0.5` will move +0.5 inches (12.7mm) to X=22.7mm (WPos). Note that G91 and G20 are only applied to this jog command.
    - `$J=G53 Y5.0` will move the machine to Y=5.0mm in the machine coordinate frame (MPos). If the work coordinate offset for the y-axis is 2.0mm, then Y is 3.0mm in (WPos).
 Jog commands behave almost identically to normal g-code streaming. Every jog command will
 return an 'ok' when the jogging motion has been parsed and is setup for execution. If a
 command is not valid or exceeds a soft-limit, Grbl will return an 'error:'. Multiple jogging commands may be queued in sequence.
 NOTE: See additional jogging documentation for details on using this command to create a low-latency joystick or rotary dial interface.
 #### `$RST=$`, `$RST=#`, and `$RST=*`- Restore Grbl settings and data to defaults
 These commands are not listed in the main Grbl `$` help message, but are available to allow users to restore parts of or all of Grbl's EEPROM data. Note: Grbl will automatically reset after executing one of these commands to ensure the system is initialized correctly.
 - `$RST=$` : Erases and restores the `$$` Grbl settings back to defaults, which is defined by the default settings file used when compiling Grbl. Often OEMs will build their Grbl firmwares with their machine-specific recommended settings. This provides users and OEMs a quick way to get back to square-one, if something went awry or if a user wants to start over.
 - `$RST=#` : Erases and zeros all G54-G59 work coordinate offsets and G28/30 positions stored in EEPROM. These are generally the values seen in the `$#` parameters printout. This provides an easy way to clear these without having to do it manually for each set with a `G20 L2/20` or `G28.1/30.1` command.
 - `$RST=*` : This clears and restores all of the EEPROM data used by Grbl. This includes `$$` settings, `$#` parameters, `$N` startup lines, and `$I` build info string. Note that this doesn't wipe the entire EEPROM, only the data areas Grbl uses. To do a complete wipe, please use the Arduino IDE's EEPROM clear example project.
 NOTE: Some OEMs may restrict some or all of these commands to prevent certain data they use from being wiped. 
 #### `$SLP` - Enable Sleep Mode
 This command will place Grbl into a de-powered sleep state, shutting down the spindle, coolant, and stepper enable pins and block any commands. It may only be exited by a soft-reset or power-cycle. Once re-initialized, Grbl will automatically enter an ALARM state, because it's not sure where it is due to the steppers being disabled.
 This feature is useful if you need to automatically de-power everything at the end of a job by adding this command at the end of your g-code program, BUT, it is highly recommended that you add commands to first move your machine to a safe parking location prior to this sleep command. It also should be emphasized that you should have a reliable CNC machine that will disable everything when its supposed to, like your spindle. Grbl is not responsible for any damage it may cause. It's never a good idea to leave your machine unattended. So, use this command with the utmost caution!
 ***
 ## Other Resources:
--- a/grbl/config.h
+++ b/grbl/config.h
@ -2,7 +2,7 @@
  config.h - compile time configuration
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -38,6 +38,7 @@
 #define CPU_MAP_ATMEGA328P // Arduino Uno CPU
 // Serial baud rate
 // #define BAUD_RATE 230400
 #define BAUD_RATE 115200
 // Define realtime command special characters. These characters are 'picked-off' directly from the
@ -46,11 +47,40 @@
 // used, if they are available per user setup. Also, extended ASCII codes (>127), which are never in
 // g-code programs, maybe selected for interface programs.
 // NOTE: If changed, manually update help message in report.c.
-#define CMD_STATUS_REPORT '?'
+
 #define CMD_FEED_HOLD '!'
 #define CMD_CYCLE_START '~'
 #define CMD_RESET 0x18 // ctrl-x.
-#define CMD_SAFETY_DOOR '@'
+#define CMD_STATUS_REPORT '?'
 #define CMD_CYCLE_START '~'
 #define CMD_FEED_HOLD '!'
 // NOTE: All override realtime commands must be in the extended ASCII character set, starting
 // at character value 128 (0x80) and up to 255 (0xFF). If the normal set of realtime commands,
 // such as status reports, feed hold, reset, and cycle start, are moved to the extended set
 // space, serial.c's RX ISR will need to be modified to accomodate the change.
 // #define CMD_RESET 0x80
 // #define CMD_STATUS_REPORT 0x81
 // #define CMD_CYCLE_START 0x82
 // #define CMD_FEED_HOLD 0x83
 #define CMD_SAFETY_DOOR 0x84
 #define CMD_JOG_CANCEL  0x85
 #define CMD_DEBUG_REPORT 0x86 // Only when DEBUG enabled, sends debug report in '{}' braces.
 #define CMD_FEED_OVR_RESET 0x90         // Restores feed override value to 100%.
 #define CMD_FEED_OVR_COARSE_PLUS 0x91
 #define CMD_FEED_OVR_COARSE_MINUS 0x92
 #define CMD_FEED_OVR_FINE_PLUS  0x93
 #define CMD_FEED_OVR_FINE_MINUS  0x94
 #define CMD_RAPID_OVR_RESET 0x95        // Restores rapid override value to 100%.
 #define CMD_RAPID_OVR_MEDIUM 0x96
 #define CMD_RAPID_OVR_LOW 0x97
 // #define CMD_RAPID_OVR_EXTRA_LOW 0x98 // *NOT SUPPORTED*
 #define CMD_SPINDLE_OVR_RESET 0x99      // Restores spindle override value to 100%.
 #define CMD_SPINDLE_OVR_COARSE_PLUS 0x9A
 #define CMD_SPINDLE_OVR_COARSE_MINUS 0x9B
 #define CMD_SPINDLE_OVR_FINE_PLUS 0x9C
 #define CMD_SPINDLE_OVR_FINE_MINUS 0x9D
 #define CMD_SPINDLE_OVR_STOP 0x9E
 #define CMD_COOLANT_FLOOD_OVR_TOGGLE 0xA0
 #define CMD_COOLANT_MIST_OVR_TOGGLE 0xA1
 // If homing is enabled, homing init lock sets Grbl into an alarm state upon power up. This forces
 // the user to perform the homing cycle (or override the locks) before doing anything else. This is
@ -113,14 +143,9 @@
 // #define LIMITS_TWO_SWITCHES_ON_AXES
 // Allows GRBL to track and report gcode line numbers.  Enabling this means that the planning buffer
-// goes from 18 or 16 to make room for the additional line number data in the plan_block_t struct
+// goes from 16 to 15 to make room for the additional line number data in the plan_block_t struct
 // #define USE_LINE_NUMBERS // Disabled by default. Uncomment to enable.
 // Allows GRBL to report the real-time feed rate.  Enabling this means that GRBL will be reporting more 
 // data with each status update.
 // NOTE: This is experimental and doesn't quite work 100%. Maybe fixed or refactored later.
 // #define REPORT_REALTIME_RATE // Disabled by default. Uncomment to enable.
 // Upon a successful probe cycle, this option provides immediately feedback of the probe coordinates
 // through an automatically generated message. If disabled, users can still access the last probe
 // coordinates through Grbl '$#' print parameters.
@ -128,7 +153,7 @@
 // Enables a second coolant control pin via the mist coolant g-code command M7 on the Arduino Uno
 // analog pin 4. Only use this option if you require a second coolant control pin.
-// NOTE: The M8 flood coolant control pin on analog pin 4 will still be functional regardless.
+// NOTE: The M8 flood coolant control pin on analog pin 3 will still be functional regardless.
 // #define ENABLE_M7 // Disabled by default. Uncomment to enable.
 // This option causes the feed hold input to act as a safety door switch. A safety door, when triggered,
@ -147,7 +172,7 @@
 // #define HOMING_CYCLE_0 (1<<X_AXIS) and #define HOMING_CYCLE_1 (1<<Y_AXIS)
 // NOTE: This configuration option alters the motion of the X and Y axes to principle of operation
 // defined at (http://corexy.com/theory.html). Motors are assumed to positioned and wired exactly as
-// described, if not, motions may move in strange directions. Grbl assumes the CoreXY A and B motors
+// described, if not, motions may move in strange directions. Grbl requires the CoreXY A and B motors
 // have the same steps per mm internally.
 // #define COREXY // Default disabled. Uncomment to enable.
@ -173,12 +198,10 @@
 // uncomment the config option USE_SPINDLE_DIR_AS_ENABLE_PIN below.
 // #define INVERT_SPINDLE_ENABLE_PIN // Default disabled. Uncomment to enable.
-// Enable all pin states feedback in status reports. Configurable with Grbl settings to print only
+// Inverts the selected coolant pin from low-disabled/high-enabled to low-enabled/high-disabled. Useful
-// the desired data, which is presented as simple binary reading of each pin as (0 (low) or 1(high)).
+// for some pre-built electronic boards.
-// The fields are printed in a particular order and settings groups are separated by '|' characters. 
+// #define INVERT_COOLANT_FLOOD_PIN // Default disabled. Uncomment to enable.
-// NOTE: This option is here for backward compatibility of the old style of pin state reports, i.e. 
+// #define INVERT_COOLANT_MIST_PIN // Default disabled. Note: Enable M7 mist coolant in config.h
 // `Lim:000`. This new `Pin:` report will be the standard going forward.
 #define REPORT_ALL_PIN_STATES // Default enabled. Comment to disable.
 // When Grbl powers-cycles or is hard reset with the Arduino reset button, Grbl boots up with no ALARM
 // by default. This is to make it as simple as possible for new users to start using Grbl. When homing
@ -188,14 +211,83 @@
 // OEMs and LinuxCNC users that would like this power-cycle behavior.
 // #define FORCE_INITIALIZATION_ALARM // Default disabled. Uncomment to enable.
 // At power-up or a reset, Grbl will check the limit switch states to ensure they are not active
 // before initialization. If it detects a problem and the hard limits setting is enabled, Grbl will
 // simply message the user to check the limits and enter an alarm state, rather than idle. Grbl will
 // not throw an alarm message.
 #define CHECK_LIMITS_AT_INIT
 // ---------------------------------------------------------------------------------------
 // ADVANCED CONFIGURATION OPTIONS:
 // Enables code for debugging purposes. Not for general use and always in constant flux.
 // #define DEBUG // Uncomment to enable. Default disabled.
 // Configure rapid, feed, and spindle override settings. These values define the max and min
 // allowable override values and the coarse and fine increments per command received. Please
 // note the allowable values in the descriptions following each define.
 #define DEFAULT_FEED_OVERRIDE           100 // 100%. Don't change this value.
 #define MAX_FEED_RATE_OVERRIDE          200 // Percent of programmed feed rate (100-255). Usually 120% or 200%
 #define MIN_FEED_RATE_OVERRIDE           10 // Percent of programmed feed rate (1-100). Usually 50% or 1%
 #define FEED_OVERRIDE_COARSE_INCREMENT   10 // (1-99). Usually 10%.
 #define FEED_OVERRIDE_FINE_INCREMENT      1 // (1-99). Usually 1%.
 #define DEFAULT_RAPID_OVERRIDE  100 // 100%. Don't change this value.
 #define RAPID_OVERRIDE_MEDIUM    50 // Percent of rapid (1-99). Usually 50%.
 #define RAPID_OVERRIDE_LOW       25 // Percent of rapid (1-99). Usually 25%.
 // #define RAPID_OVERRIDE_EXTRA_LOW 5 // *NOT SUPPORTED* Percent of rapid (1-99). Usually 5%.
 #define DEFAULT_SPINDLE_SPEED_OVERRIDE    100 // 100%. Don't change this value.
 #define MAX_SPINDLE_SPEED_OVERRIDE        200 // Percent of programmed spindle speed (100-255). Usually 200%.
 #define MIN_SPINDLE_SPEED_OVERRIDE         50 // Percent of programmed spindle speed (1-100). Usually 50%.
 #define SPINDLE_OVERRIDE_COARSE_INCREMENT  10 // (1-99). Usually 10%.
 #define SPINDLE_OVERRIDE_FINE_INCREMENT     1 // (1-99). Usually 1%.
 // When a M2 or M30 program end command is executed, most g-code states are restored to their defaults.
 // This compile-time option includes the restoring of the feed, rapid, and spindle speed override values
 // to their default values at program end.
 #define RESTORE_OVERRIDES_AFTER_PROGRAM_END // Default enabled. Comment to disable.
 // Enables minimal reporting feedback mode for GUIs, where human-readable strings are not as important.
 // This saves nearly 2KB of flash space and may allow enough space to install other/future features.
 // GUIs will need to install a look-up table for the error-codes that Grbl sends back in their place.
 // NOTE: This feature is new and experimental. Make sure the GUI you are using supports this mode.
-// #define REPORT_GUI_MODE // Default disabled. Uncomment to enable.
+#define REPORT_GUI_MODE // Default enabled. Comment to disable.
 // The status report change for Grbl v1.0 and after also removed the ability to disable/enable most data
 // fields from the report. This caused issues for GUI developers, who've had to manage several scenarios
 // and configurations. The increased efficiency of the new reporting style allows for all data fields to 
 // be sent without potential performance issues.
 // NOTE: The options below are here only provide a way to disable certain data fields if a unique
 // situation demands it, but be aware GUIs may depend on this data. If disabled, it may not be compatible.
 #define REPORT_FIELD_BUFFER_STATE // Default enabled. Comment to disable.
 #define REPORT_FIELD_PIN_STATE // Default enabled. Comment to disable.
 #define REPORT_FIELD_CURRENT_RATE // Default enabled. Comment to disable.
 #define REPORT_FIELD_WORK_COORD_OFFSET // Default enabled. Comment to disable.
 #define REPORT_FIELD_OVERRIDES // Default enabled. Comment to disable.
 #define REPORT_FIELD_LINE_NUMBERS // Default enabled. Comment to disable.
 // Some status report data isn't necessary for realtime, only intermittently, because the values don't
 // change often. The following macros configures how many times a status report needs to be called before
 // the associated data is refreshed and included in the status report. However, if one of these value
 // changes, Grbl will automatically include this data in the next status report, regardless of what the
 // count is at the time. This helps reduce the communication overhead involved with high frequency reporting
 // and agressive streaming. There is also a busy and an idle refresh count, which sets up Grbl to send
 // refreshes more often when its not doing anything important. With a good GUI, this data doesn't need
 // to be refreshed very often, on the order of a several seconds.
 // NOTE: The refresh count cannot be set to zero and must be one or greater.
 #define REPORT_OVR_REFRESH_BUSY_COUNT 20  // (1-255)
 #define REPORT_OVR_REFRESH_IDLE_COUNT 10  // (1-255) Must be less than or equal to the busy count
 #define REPORT_WCO_REFRESH_BUSY_COUNT 30  // (1-255)
 #define REPORT_WCO_REFRESH_IDLE_COUNT 10  // (1-255) Must be less than or equal to the busy count
 // COMPATIBILITY OPTIONS:
 // Grbl v1.0 and later altered the formatting of the realtime status reports to make it more consistent
 // for parsing with cleaner delimiters and optimized messages. To use Grbl v0.9-style status reporting,
 // enable this compile option. This is generally useful if older GUIs require this formatting.
 // #define USE_CLASSIC_REALTIME_REPORT
 // #define REPORT_ALL_PIN_STATES // Default disabled. Comment to enable. NOTE: Compatible with old-style reports only.
 // #define REPORT_REALTIME_RATE // Disabled by default. Uncomment to enable.
 // The temporal resolution of the acceleration management subsystem. A higher number gives smoother
 // acceleration, particularly noticeable on machines that run at very high feedrates, but may negatively
@ -325,10 +417,10 @@
 // The number of linear motions in the planner buffer to be planned at any give time. The vast
 // majority of RAM that Grbl uses is based on this buffer size. Only increase if there is extra
-// available RAM, like when re-compiling for a Mega or Sanguino. Or decrease if the Arduino
+// available RAM, like when re-compiling for a Mega2560. Or decrease if the Arduino begins to
-// begins to crash due to the lack of available RAM or if the CPU is having trouble keeping
+// crash due to the lack of available RAM or if the CPU is having trouble keeping up with planning
-// up with planning new incoming motions as they are executed. 
+// new incoming motions as they are executed.
-// #define BLOCK_BUFFER_SIZE 18  // Uncomment to override default in planner.h.
+// #define BLOCK_BUFFER_SIZE 17 // Uncomment to override default in planner.h.
 // Governs the size of the intermediary step segment buffer between the step execution algorithm
 // and the planner blocks. Each segment is set of steps executed at a constant velocity over a
@ -354,28 +446,16 @@
 // increase the receive buffer if a deeper receive buffer is needed for streaming and avaiable
 // memory allows. The send buffer primarily handles messages in Grbl. Only increase if large
 // messages are sent and Grbl begins to stall, waiting to send the rest of the message.
-// NOTE: Buffer size values must be greater than zero and less than 256.
+// NOTE: Grbl generates an average status report in about 0.5msec, but the serial TX stream at
-// #define RX_BUFFER_SIZE 128 // Uncomment to override defaults in serial.h
+// 115200 baud will take 5 msec to transmit a typical 55 character report. Worst case reports are
-// #define TX_BUFFER_SIZE 64
+// around 90-100 characters. As long as the serial TX buffer doesn't get continually maxed, Grbl
 // will continue operating efficiently. Size the TX buffer around the size of a worst-case report.
 // #define RX_BUFFER_SIZE 128 // (1-254) Uncomment to override defaults in serial.h
 // #define TX_BUFFER_SIZE 90  // (1-254)
-// Toggles XON/XOFF software flow control for serial communications. Not officially supported
+// Configures the position after a probing cycle during Grbl's check mode. Disabled sets
-// due to problems involving the Atmega8U2 USB-to-serial chips on current Arduinos. The firmware
+// the position to the probe target, when enabled sets the position to the start position.
-// on these chips do not support XON/XOFF flow control characters and the intermediate buffer 
+// #define SET_CHECK_MODE_PROBE_TO_START // Default disabled. Uncomment to enable.
 // in the chips cause latency and overflow problems with standard terminal programs. However, 
 // using specifically-programmed UI's to manage this latency problem has been confirmed to work.
 // As well as, older FTDI FT232RL-based Arduinos(Duemilanove) are known to work with standard
 // terminal programs since their firmware correctly manage these XON/XOFF characters. In any
 // case, please report any successes to grbl administrators!
 // #define ENABLE_XONXOFF // Default disabled. Uncomment to enable.
 // A simple software debouncing feature for hard limit switches. When enabled, the interrupt 
 // monitoring the hard limit switch pins will enable the Arduino's watchdog timer to re-check 
 // the limit pin state after a delay of about 32msec. This can help with CNC machines with 
 // problematic false triggering of their hard limit switches, but it WILL NOT fix issues with 
 // electrical interference on the signal cables from external sources. It's recommended to first
 // use shielded signal cables with their shielding connected to ground (old USB/computer cables 
 // work well and are cheap to find) and wire in a low-pass circuit into each limit pin.
 // #define ENABLE_SOFTWARE_DEBOUNCE // Default disabled. Uncomment to enable.
 // Force Grbl to check the state of the hard limit switches when the processor detects a pin
 // change inside the hard limit ISR routine. By default, Grbl will trigger the hard limits
@ -397,6 +477,49 @@
 // #define HOMING_AXIS_SEARCH_SCALAR  1.5 // Uncomment to override defaults in limits.c.
 // #define HOMING_AXIS_LOCATE_SCALAR  10.0 // Uncomment to override defaults in limits.c.
 // Enable the '$RST=*', '$RST=$', and '$RST=#' eeprom restore commands. There are cases where
 // these commands may be undesirable. Simply comment the desired macro to disable it.
 // NOTE: See SETTINGS_RESTORE_ALL macro for customizing the `$RST=*` command.
 #define ENABLE_RESTORE_EEPROM_WIPE_ALL         // '$RST=*' Default enabled. Comment to disable.
 #define ENABLE_RESTORE_EEPROM_DEFAULT_SETTINGS // '$RST=$' Default enabled. Comment to disable.
 #define ENABLE_RESTORE_EEPROM_CLEAR_PARAMETERS // '$RST=#' Default enabled. Comment to disable.
 // Defines the EEPROM data restored upon a settings version change and `$RST=*` command. Whenever the
 // the settings or other EEPROM data structure changes between Grbl versions, Grbl will automatically
 // wipe and restore the EEPROM. This macro controls what data is wiped and restored. This is useful
 // particularily for OEMs that need to retain certain data. For example, the BUILD_INFO string can be
 // written into the Arduino EEPROM via a seperate .INO sketch to contain product data. Altering this
 // macro to not restore the build info EEPROM will ensure this data is retained after firmware upgrades.
 // NOTE: Uncomment to override defaults in settings.h
 // #define SETTINGS_RESTORE_ALL (SETTINGS_RESTORE_DEFAULTS | SETTINGS_RESTORE_PARAMETERS | SETTINGS_RESTORE_STARTUP_LINES | SETTINGS_RESTORE_BUILD_INFO)
 // Enable the '$I=(string)' build info write command. If disabled, any existing build info data must
 // be placed into EEPROM via external means with a valid checksum value. This macro option is useful
 // to prevent this data from being over-written by a user, when used to store OEM product data.
 // NOTE: See the included grblWrite_BuildInfo.ino example file to write this string seperately.
 #define ENABLE_BUILD_INFO_WRITE_COMMAND // '$I=' Default enabled. Comment to disable.
 // AVR processors require all interrupts to be disabled during an EEPROM write. This includes both
 // the stepper ISRs and serial comm ISRs. In the event of a long EEPROM write, this ISR pause can
 // cause active stepping to lose position and serial receive data to be lost. This configuration
 // option forces the planner buffer to completely empty whenever the EEPROM is written to prevent
 // any chance of lost steps.
 // However, this doesn't prevent issues with lost serial RX data during an EEPROM write, especially
 // if a GUI is premptively filling up the serial RX buffer simultaneously. It's highly advised for
 // GUIs to flag these gcodes (G10,G28.1,G30.1) to always wait for an 'ok' after a block containing
 // one of these commands before sending more data to eliminate this issue.
 // NOTE: Most EEPROM write commands are implicitly blocked during a job (all '$' commands). However,
 // coordinate set g-code commands (G10,G28/30.1) are not, since they are part of an active streaming
 // job. At this time, this option only forces a planner buffer sync with these g-code commands.
 #define FORCE_BUFFER_SYNC_DURING_EEPROM_WRITE // Default enabled. Comment to disable.
 // In Grbl v0.9 and prior, there is an old outstanding bug where the `WPos:` work position reported
 // may not correlate to what is executing, because `WPos:` is based on the g-code parser state, which
 // can be several motions behind. This option forces the planner buffer to empty, sync, and stop
 // motion whenever there is a command that alters the work coordinate offsets `G10,G43.1,G92,G54-59`.
 // This is the simplest way to ensure `WPos:` is always correct. Fortunately, it's exceedingly rare
 // that any of these commands are used need continuous motions through them.
 #define FORCE_BUFFER_SYNC_DURING_WCO_CHANGE // Default enabled. Comment to disable.
 // Enables and configures parking motion methods upon a safety door state. Primarily for OEMs
 // that desire this feature for their integrated machines. At the moment, Grbl assumes that
@ -416,8 +539,8 @@
 // Configure options for the parking motion, if enabled.
 #define PARKING_AXIS Z_AXIS // Define which axis that performs the parking motion
 #define PARKING_TARGET -5.0 // Parking axis target. In mm, as machine coordinate [-max_travel,0].
-#define PARKING_RATE -1.0 // Parking fast rate after pull-out. In mm/min or (-1.0) for seek rate.
+#define PARKING_RATE 500.0 // Parking fast rate after pull-out in mm/min.
-#define PARKING_PULLOUT_RATE 250.0 // Pull-out/plunge slow feed rate in mm/min.
+#define PARKING_PULLOUT_RATE 100.0 // Pull-out/plunge slow feed rate in mm/min.
 #define PARKING_PULLOUT_INCREMENT 5.0 // Spindle pull-out and plunge distance in mm. Incremental distance.
                                      // Must be positive value or equal to zero.
--- a/grbl/coolant_control.c
+++ b/grbl/coolant_control.c
@ -2,7 +2,7 @@
  coolant_control.c - coolant control methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -23,38 +23,44 @@
 void coolant_init()
 {
-  COOLANT_FLOOD_DDR |= (1 << COOLANT_FLOOD_BIT);
+  COOLANT_FLOOD_DDR |= (1 << COOLANT_FLOOD_BIT); // Configure as output pin
  #ifdef ENABLE_M7
    COOLANT_MIST_DDR |= (1 << COOLANT_MIST_BIT);
  #endif
-  coolant_stop();
+  coolant_set_state(COOLANT_DISABLE);
 }
 void coolant_stop()
 {
  COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
  #ifdef ENABLE_M7
    COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
  #endif
 }
 void coolant_set_state(uint8_t mode)
 {
-  if (sys.abort) { return; } // Block during abort.
+  if (mode & COOLANT_FLOOD_ENABLE) {
-  
+    #ifdef INVERT_COOLANT_FLOOD_PIN
-  if (mode == COOLANT_FLOOD_ENABLE) {
+      COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
    #else
      COOLANT_FLOOD_PORT |= (1 << COOLANT_FLOOD_BIT);
-
+    #endif
  } else {
    #ifdef INVERT_COOLANT_FLOOD_PIN
      COOLANT_FLOOD_PORT |= (1 << COOLANT_FLOOD_BIT);
    #else
      COOLANT_FLOOD_PORT &= ~(1 << COOLANT_FLOOD_BIT);
    #endif
  }
  #ifdef ENABLE_M7
-    } else if (mode == COOLANT_MIST_ENABLE) {
+    if (mode & COOLANT_MIST_ENABLE) {
      #ifdef INVERT_COOLANT_MIST_PIN
        COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
      #else
        COOLANT_MIST_PORT |= (1 << COOLANT_MIST_BIT);
      #endif
    } else {
-    coolant_stop();
+      #ifdef INVERT_COOLANT_MIST_PIN
        COOLANT_MIST_PORT |= (1 << COOLANT_MIST_BIT);
      #else
        COOLANT_MIST_PORT &= ~(1 << COOLANT_MIST_BIT);
      #endif
    }
  #endif
 }
@ -62,5 +68,6 @@ void coolant_run(uint8_t mode)
 {
  if (sys.state == STATE_CHECK_MODE) { return; }
  protocol_buffer_synchronize(); // Ensure coolant turns on when specified in program.
  if (sys.abort) { return; } // Block during abort.
  coolant_set_state(mode);
 }
--- a/grbl/coolant_control.h
+++ b/grbl/coolant_control.h
@ -2,7 +2,7 @@
  coolant_control.h - spindle control methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -23,7 +23,6 @@
 void coolant_init();
 void coolant_stop();
 void coolant_set_state(uint8_t mode);
 void coolant_run(uint8_t mode);
--- a/grbl/cpu_map.h
+++ b/grbl/cpu_map.h
@ -2,7 +2,7 @@
  cpu_map.h - CPU and pin mapping configuration file
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -93,16 +93,12 @@
  #endif
  // Define flood and mist coolant enable output pins.
  // NOTE: Uno analog pins 4 and 5 are reserved for an i2c interface, and may be installed at
  // a later date if flash and memory space allows.
  #define COOLANT_FLOOD_DDR   DDRC
  #define COOLANT_FLOOD_PORT  PORTC
  #define COOLANT_FLOOD_BIT   3  // Uno Analog Pin 3
  #ifdef ENABLE_M7 // Mist coolant disabled by default. See config.h to enable/disable.
  #define COOLANT_MIST_DDR   DDRC
  #define COOLANT_MIST_PORT  PORTC
-    #define COOLANT_MIST_BIT   4 // Uno Analog Pin 4
+  #define COOLANT_MIST_BIT   4  // Uno Analog Pin 3
  #endif  
  // Define user-control controls (cycle start, reset, feed hold) input pins.
  // NOTE: All CONTROLs pins must be on the same port and not on a port with other input pins (limits).
@ -126,24 +122,26 @@
  #define PROBE_BIT       5  // Uno Analog Pin 5
  #define PROBE_MASK      (1<<PROBE_BIT)
-  // Start of PWM & Stepper Enabled Spindle
+  // Variable spindle configuration below. Do not change unless you know what you are doing.
-  #ifdef VARIABLE_SPINDLE
+  // NOTE: Only used when variable spindle is enabled.
    // Advanced Configuration Below You should not need to touch these variables
  #define SPINDLE_PWM_MAX_VALUE     255.0 // Don't change. 328p fast PWM mode fixes top value as 255.
  #define SPINDLE_PWM_OFF_VALUE     0.0
  #define SPINDLE_TCCRA_REGISTER	  TCCR2A
  #define SPINDLE_TCCRB_REGISTER	  TCCR2B
  #define SPINDLE_OCR_REGISTER      OCR2A
  #define SPINDLE_COMB_BIT	        COM2A1
-    // 1/8 Prescaler, 8-bit Fast PWM mode. Translates to about 7.8kHz PWM frequency.
+  // Prescaled, 8-bit Fast PWM mode.
-    #define SPINDLE_TCCRA_INIT_MASK   ((1<<WGM20) | (1<<WGM21))
+  #define SPINDLE_TCCRA_INIT_MASK   ((1<<WGM20) | (1<<WGM21))  // Configures fast PWM mode.
-    #define SPINDLE_TCCRB_INIT_MASK   (1<<CS21)
+  // #define SPINDLE_TCCRB_INIT_MASK   (1<<CS21)                  // 1/8 prescaler -> 7.8kHz (Used in v0.9)
  // #define SPINDLE_TCCRB_INIT_MASK   ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
  #define SPINDLE_TCCRB_INIT_MASK   (1<<CS22)               // 1/64 prescaler -> 0.98kHz
  // NOTE: On the 328p, these must be the same as the SPINDLE_ENABLE settings.
  #define SPINDLE_PWM_DDR	  DDRB
  #define SPINDLE_PWM_PORT  PORTB
  #define SPINDLE_PWM_BIT	  3    // Uno Digital Pin 11
  #endif // End of VARIABLE_SPINDLE
 #endif
--- a/grbl/defaults.h
+++ b/grbl/defaults.h
@ -2,7 +2,7 @@
  defaults.h - defaults settings configuration file
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -47,7 +47,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK 0
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.01 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -55,6 +55,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -87,7 +89,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<Y_AXIS)|(1<<Z_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.01 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // true
@ -95,6 +97,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 50.0 // mm/min
@ -130,7 +134,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<Y_AXIS)|(1<<Z_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -138,6 +142,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -173,7 +179,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<X_AXIS)|(1<<Z_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -181,6 +187,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -215,7 +223,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<X_AXIS)|(1<<Z_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK 255 // All enabled
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.01 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -223,6 +231,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 100.0 // mm/min
@ -258,7 +268,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<X_AXIS)|(1<<Y_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -266,6 +276,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 3 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -301,7 +313,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<X_AXIS)|(1<<Y_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 255 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -309,6 +321,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 3 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -342,7 +356,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK ((1<<Y_AXIS))
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -350,6 +364,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -379,7 +395,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK 0
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.02 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -387,6 +403,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
@ -416,7 +434,7 @@
  #define DEFAULT_STEPPING_INVERT_MASK 0
  #define DEFAULT_DIRECTION_INVERT_MASK 0
  #define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
-  #define DEFAULT_STATUS_REPORT_MASK ((BITFLAG_RT_STATUS_MACHINE_POSITION)|(BITFLAG_RT_STATUS_WORK_POSITION))
+  #define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
  #define DEFAULT_JUNCTION_DEVIATION 0.01 // mm
  #define DEFAULT_ARC_TOLERANCE 0.002 // mm
  #define DEFAULT_REPORT_INCHES 0 // false
@ -424,6 +442,8 @@
  #define DEFAULT_INVERT_LIMIT_PINS 0 // false
  #define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
  #define DEFAULT_HARD_LIMIT_ENABLE 0  // false
  #define DEFAULT_INVERT_PROBE_PIN 0 // false
  #define DEFAULT_LASER_MODE 0 // false
  #define DEFAULT_HOMING_ENABLE 0  // false
  #define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
  #define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
--- a/grbl/examples/grblWrite_BuildInfo/grblWrite_BuildInfo.ino
+++ b/grbl/examples/grblWrite_BuildInfo/grblWrite_BuildInfo.ino
@ -0,0 +1,109 @@
 /***********************************************************************
 This sketch writes a `$I` build info string directly into Arduino EEPROM
 To use:
 - Just alter the "build_info_line" string to whatever you'd like. Then 
  compile and upload this sketch to your Arduino.
 - If your Arduino is blinking slowly, your string has already been 
  written to your EEPROM and been verified by checksums! That's it!
 - If you Arduino LED is blinking fast, something went wrong and the 
  checksums don't match. You can optionally connect to the Arduino via
  the serial monitor, and the sketch will show what its doing.
 NOTE: This sketch is provided as a tool template for OEMs who may need
 to restrict users from altering their build info, so they can place
 important product information here when enabling the restriction.
 NOTE: When uploading Grbl to the Arduino with this sketch on it, make
 sure you see the slow blink before you start the upload process. This
 ensures you aren't flashing Grbl when it's in mid-write of the EEPROM.
 Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC
 Released under the MIT-license. See license.txt for details.
 ***********************************************************************/
 #include <avr/pgmspace.h>
 #include <EEPROM.h>
 #define SERIAL_BAUD_RATE 115200
 #define LINE_LENGTH 80U    // Grbl line length
 #define BYTE_LOCATION 942U // Grbl build info EEPROM address.
 // ----- CHANGE THIS LINE -----
 char build_info_line[LINE_LENGTH] = "Testing123.";
 // -----------------------------
 uint8_t status = false;
 int ledPin = 13;                 // LED connected to digital pin 13
 void setup() {
  Serial.begin(SERIAL_BAUD_RATE);
  delay(500);
  uint32_t address = BYTE_LOCATION;
  uint32_t size = LINE_LENGTH;
  char *write_pointer = (char*)build_info_line;
  uint8_t write_checksum = 0;
  for (; size>0; size--) { 
    write_checksum = (write_checksum << 1) || (write_checksum >> 7);
    write_checksum += *write_pointer;
    EEPROM.put(address++, *(write_pointer++)); 
  }
  EEPROM.put(address,write_checksum);
  Serial.print(F("-> Writing line to EEPROM: '"));
  Serial.print(build_info_line);
  Serial.print(F("'\n\r-> Write checksum: "));
  Serial.println(write_checksum,DEC);
  size = LINE_LENGTH;
  address = BYTE_LOCATION;
  uint8_t data = 0;
  char read_line[LINE_LENGTH];
  char *read_pointer = (char*)read_line;
  uint8_t read_checksum = 0;
  uint8_t stored_checksum = 0;
  for(; size > 0; size--) { 
    data = EEPROM.read(address++);
    read_checksum = (read_checksum << 1) || (read_checksum >> 7);
    read_checksum += data;    
    *(read_pointer++) = data; 
  }
  stored_checksum = EEPROM.read(address);
  Serial.print(F("<- Reading line from EEPROM: '"));
  Serial.print(read_line);
  Serial.print("'\n\r<- Read checksum: ");
  Serial.println(read_checksum,DEC);
  if ((read_checksum == write_checksum) && (read_checksum == stored_checksum)) {
    status = true;
    Serial.print(F("SUCCESS! All checksums match!\r\n"));
  } else {
    if (write_checksum != stored_checksum) {
      Serial.println(F("ERROR! Write and stored EEPROM checksums don't match!"));
    } else {
      Serial.println(F("ERROR! Read and stored checksums don't match!"));
    }
  }
  pinMode(ledPin, OUTPUT);      // sets the digital pin as output
 }
 void loop() {
  // Blink to let user know EEPROM write status. 
  // Slow blink is 'ok'. Fast blink is an 'error'.
  digitalWrite(ledPin, HIGH);   // sets the LED on
  if (status) { delay(1500); } // Slow blink
  else { delay(100); } // Rapid blink
  digitalWrite(ledPin, LOW);    // sets the LED off
  if (status) { delay(1500); }
  else { delay(100); } 
 }
--- a/grbl/examples/grblWrite_BuildInfo/license.txt
+++ b/grbl/examples/grblWrite_BuildInfo/license.txt
@ -0,0 +1,21 @@
 The MIT License (MIT)
 Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:
 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
--- a/grbl/gcode.c
+++ b/grbl/gcode.c
@ -2,7 +2,7 @@
  gcode.c - rs274/ngc parser.
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -24,7 +24,7 @@
 // NOTE: Max line number is defined by the g-code standard to be 99999. It seems to be an
 // arbitrary value, and some GUIs may require more. So we increased it based on a max safe
 // value when converting a float (7.2 digit precision)s to an integer.
-#define MAX_LINE_NUMBER 9999999 
+#define MAX_LINE_NUMBER 10000000
 #define AXIS_COMMAND_NONE 0
 #define AXIS_COMMAND_NON_MODAL 1
@ -53,19 +53,10 @@ void gc_init()
 // limit pull-off routines.
 void gc_sync_position()
 {
-  system_convert_array_steps_to_mpos(gc_state.position,sys.position);
+  system_convert_array_steps_to_mpos(gc_state.position,sys_position);
 }
 static uint8_t gc_check_same_position(float *pos_a, float *pos_b) 
 {
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    if (pos_a[idx] != pos_b[idx]) { return(false); }
  }
  return(true);
 }
 // Executes one line of 0-terminated G-Code. The line is assumed to contain only uppercase
 // characters and signed floating point values (no whitespace). Comments and block delete
 // characters have been removed. In this function, all units and positions are converted and
@ -82,11 +73,10 @@ uint8_t gc_execute_line(char *line)
  memset(&gc_block, 0, sizeof(parser_block_t)); // Initialize the parser block struct.
  memcpy(&gc_block.modal,&gc_state.modal,sizeof(gc_modal_t)); // Copy current modes
  uint8_t axis_command = AXIS_COMMAND_NONE;
  uint8_t axis_0, axis_1, axis_linear;
  uint8_t coord_select = 0; // Tracks G10 P coordinate selection for execution
  float coordinate_data[N_AXIS]; // Multi-use variable to store coordinate data for execution
  float parameter_data[N_AXIS]; // Multi-use variable to store parameter data for execution
  // Initialize bitflag tracking variables for axis indices compatible operations.
  uint8_t axis_words = 0; // XYZ tracking
@ -96,6 +86,15 @@ uint8_t gc_execute_line(char *line)
  uint16_t command_words = 0; // G and M command words. Also used for modal group violations.
  uint16_t value_words = 0; // Value words.
  // Determine if the line is a jogging motion or a normal g-code block.
  uint8_t is_jog_motion = false;
  if (line[0] == '$') { // NOTE: `$J=` already parsed when passed to this function.
    // Set G1 and G94 enforced modes to ensure accurate error checks.
    is_jog_motion = true;
    gc_block.modal.motion = MOTION_MODE_LINEAR;
    gc_block.modal.feed_rate = FEED_RATE_MODE_UNITS_PER_MIN;
  }
  /* -------------------------------------------------------------------------------------
     STEP 2: Import all g-code words in the block line. A g-code word is a letter followed by
     a number, which can either be a 'G'/'M' command or sets/assigns a command value. Also,
@ -103,11 +102,13 @@ uint8_t gc_execute_line(char *line)
     words, and for negative values set for the value words F, N, P, T, and S. */
  uint8_t word_bit; // Bit-value for assigning tracking variables
-  uint8_t char_counter = 0;  
+  uint8_t char_counter;
  char letter;
  float value;
  uint8_t int_value = 0;
  uint16_t mantissa = 0;
  if (is_jog_motion) { char_counter = 3; } // Start parsing after `$J=`
  else { char_counter = 0; }
  while (line[char_counter] != 0) { // Loop until no more g-code words in line.
@ -300,9 +301,10 @@ uint8_t gc_execute_line(char *line)
            }
            break;
          #ifdef ENABLE_M7
-          case 7:
+            case 7: case 8: case 9:
-         #endif
+          #else
            case 8: case 9:
          #endif
            word_bit = MODAL_GROUP_M8;
            switch(int_value) {
              #ifdef ENABLE_M7
@ -417,6 +419,11 @@ uint8_t gc_execute_line(char *line)
  // [2. Set feed rate mode ]: G93 F word missing with G1,G2/3 active, implicitly or explicitly. Feed rate
  //   is not defined after switching to G94 from G93.
  // NOTE: For jogging, ignore prior feed rate mode. Enforce G94 and check for required F word.
  if (is_jog_motion) {
    if (bit_isfalse(value_words,bit(WORD_F))) { FAIL(STATUS_GCODE_UNDEFINED_FEED_RATE); }
    if (gc_block.modal.units == UNITS_MODE_INCHES) { gc_block.values.f *= MM_PER_INCH; }
  } else {
    if (gc_block.modal.feed_rate == FEED_RATE_MODE_INVERSE_TIME) { // = G93
      // NOTE: G38 can also operate in inverse time, but is undefined as an error. Missing F word check added here.
      if (axis_command == AXIS_COMMAND_MOTION_MODE) {
@ -446,6 +453,7 @@ uint8_t gc_execute_line(char *line)
        }
      } // Else, switching to G94 from G93, so don't push last state feed rate. Its undefined or the passed F word value.
    }
  }
  // bit_false(value_words,bit(WORD_F)); // NOTE: Single-meaning value word. Set at end of error-checking.
  // [4. Set spindle speed ]: S is negative (done.)
@ -516,11 +524,12 @@ uint8_t gc_execute_line(char *line)
  // is active. The read pauses the processor temporarily and may cause a rare crash. For
  // future versions on processors with enough memory, all coordinate data should be stored
  // in memory and written to EEPROM only when there is not a cycle active.
-  memcpy(coordinate_data,gc_state.coord_system,sizeof(gc_state.coord_system));
+  float block_coord_system[N_AXIS];
  memcpy(block_coord_system,gc_state.coord_system,sizeof(gc_state.coord_system));
  if ( bit_istrue(command_words,bit(MODAL_GROUP_G12)) ) { // Check if called in block
    if (gc_block.modal.coord_select > N_COORDINATE_SYSTEM) { FAIL(STATUS_GCODE_UNSUPPORTED_COORD_SYS); } // [Greater than N sys]
    if (gc_state.modal.coord_select != gc_block.modal.coord_select) {
-      if (!(settings_read_coord_data(gc_block.modal.coord_select,coordinate_data))) { FAIL(STATUS_SETTING_READ_FAIL); } 
+      if (!(settings_read_coord_data(gc_block.modal.coord_select,block_coord_system))) { FAIL(STATUS_SETTING_READ_FAIL); }
    }
  }
@ -552,21 +561,24 @@ uint8_t gc_execute_line(char *line)
      // Determine coordinate system to change and try to load from EEPROM.
      if (coord_select > 0) { coord_select--; } // Adjust P1-P6 index to EEPROM coordinate data indexing.
      else { coord_select = gc_block.modal.coord_select; } // Index P0 as the active coordinate system
      if (!settings_read_coord_data(coord_select,parameter_data)) { FAIL(STATUS_SETTING_READ_FAIL); } // [EEPROM read fail]
-      // Pre-calculate the coordinate data changes. NOTE: Uses parameter_data since coordinate_data may be in use by G54-59.
+      // NOTE: Store parameter data in IJK values. By rule, they are not in use with this command.
      if (!settings_read_coord_data(coord_select,gc_block.values.ijk)) { FAIL(STATUS_SETTING_READ_FAIL); } // [EEPROM read fail]
      // Pre-calculate the coordinate data changes.
      for (idx=0; idx<N_AXIS; idx++) { // Axes indices are consistent, so loop may be used.
        // Update axes defined only in block. Always in machine coordinates. Can change non-active system.
        if (bit_istrue(axis_words,bit(idx)) ) {
          if (gc_block.values.l == 20) {
            // L20: Update coordinate system axis at current position (with modifiers) with programmed value
-            parameter_data[idx] = gc_state.position[idx]-gc_state.coord_offset[idx]-gc_block.values.xyz[idx];
+            // WPos = MPos - WCS - G92 - TLO  ->  WCS = MPos - G92 - TLO - WPos
-            if (idx == TOOL_LENGTH_OFFSET_AXIS) { parameter_data[idx] -= gc_state.tool_length_offset; }
+            gc_block.values.ijk[idx] = gc_state.position[idx]-gc_state.coord_offset[idx]-gc_block.values.xyz[idx];
            if (idx == TOOL_LENGTH_OFFSET_AXIS) { gc_block.values.ijk[idx] -= gc_state.tool_length_offset; }
          } else {
            // L2: Update coordinate system axis to programmed value.
-            parameter_data[idx] = gc_block.values.xyz[idx]; 
+            gc_block.values.ijk[idx] = gc_block.values.xyz[idx];
          }
          }
        } // Else, keep current stored value.
      }
      break;
    case NON_MODAL_SET_COORDINATE_OFFSET:
@ -577,7 +589,8 @@ uint8_t gc_execute_line(char *line)
      // active coordinate system is selected, but is still active unless G92.1 disables it.
      for (idx=0; idx<N_AXIS; idx++) { // Axes indices are consistent, so loop may be used.
        if (bit_istrue(axis_words,bit(idx)) ) {
-          gc_block.values.xyz[idx] = gc_state.position[idx]-coordinate_data[idx]-gc_block.values.xyz[idx];
+          // WPos = MPos - WCS - G92 - TLO  ->  G92 = MPos - WCS - TLO - WPos
          gc_block.values.xyz[idx] = gc_state.position[idx]-block_coord_system[idx]-gc_block.values.xyz[idx];
          if (idx == TOOL_LENGTH_OFFSET_AXIS) { gc_block.values.xyz[idx] -= gc_state.tool_length_offset; }
        } else {
          gc_block.values.xyz[idx] = gc_state.coord_offset[idx];
@ -602,7 +615,7 @@ uint8_t gc_execute_line(char *line)
              if (gc_block.non_modal_command != NON_MODAL_ABSOLUTE_OVERRIDE) {
                // Apply coordinate offsets based on distance mode.
                if (gc_block.modal.distance == DISTANCE_MODE_ABSOLUTE) {
-                  gc_block.values.xyz[idx] += coordinate_data[idx] + gc_state.coord_offset[idx];
+                  gc_block.values.xyz[idx] += block_coord_system[idx] + gc_state.coord_offset[idx];
                  if (idx == TOOL_LENGTH_OFFSET_AXIS) { gc_block.values.xyz[idx] += gc_state.tool_length_offset; }
                } else {  // Incremental mode
                  gc_block.values.xyz[idx] += gc_state.position[idx];
@ -619,15 +632,16 @@ uint8_t gc_execute_line(char *line)
        case NON_MODAL_GO_HOME_1: // G30
          // [G28/30 Errors]: Cutter compensation is enabled.
          // Retreive G28/30 go-home position data (in machine coordinates) from EEPROM
          // NOTE: Store parameter data in IJK values. By rule, they are not in use with this command.
          if (gc_block.non_modal_command == NON_MODAL_GO_HOME_0) {
-            if (!settings_read_coord_data(SETTING_INDEX_G28,parameter_data)) { FAIL(STATUS_SETTING_READ_FAIL); }
+            if (!settings_read_coord_data(SETTING_INDEX_G28,gc_block.values.ijk)) { FAIL(STATUS_SETTING_READ_FAIL); }
          } else { // == NON_MODAL_GO_HOME_1
-            if (!settings_read_coord_data(SETTING_INDEX_G30,parameter_data)) { FAIL(STATUS_SETTING_READ_FAIL); }
+            if (!settings_read_coord_data(SETTING_INDEX_G30,gc_block.values.ijk)) { FAIL(STATUS_SETTING_READ_FAIL); }
          }
          if (axis_words) {
            // Move only the axes specified in secondary move.
            for (idx=0; idx<N_AXIS; idx++) {
-              if (!(axis_words & (1<<idx))) { parameter_data[idx] = gc_state.position[idx]; }
+              if (!(axis_words & (1<<idx))) { gc_block.values.ijk[idx] = gc_state.position[idx]; }
            }
          } else {
            axis_command = AXIS_COMMAND_NONE; // Set to none if no intermediate motion.
@ -698,7 +712,7 @@ uint8_t gc_execute_line(char *line)
          if (value_words & bit(WORD_R)) { // Arc Radius Mode
            bit_false(value_words,bit(WORD_R));
-            if (gc_check_same_position(gc_state.position, gc_block.values.xyz)) { FAIL(STATUS_GCODE_INVALID_TARGET); } // [Invalid target]
+            if (isequal_position_vector(gc_state.position, gc_block.values.xyz)) { FAIL(STATUS_GCODE_INVALID_TARGET); } // [Invalid target]
            // Convert radius value to proper units.
            if (gc_block.modal.units == UNITS_MODE_INCHES) { gc_block.values.r *= MM_PER_INCH; }
@ -822,7 +836,7 @@ uint8_t gc_execute_line(char *line)
          //   an error, it issues an alarm to prevent further motion to the probe. It's also done there to
          //   allow the planner buffer to empty and move off the probe trigger before another probing cycle.
          if (!axis_words) { FAIL(STATUS_GCODE_NO_AXIS_WORDS); } // [No axis words]
-          if (gc_check_same_position(gc_state.position, gc_block.values.xyz)) { FAIL(STATUS_GCODE_INVALID_TARGET); } // [Invalid target]
+          if (isequal_position_vector(gc_state.position, gc_block.values.xyz)) { FAIL(STATUS_GCODE_INVALID_TARGET); } // [Invalid target]
          break;
      }
    }
@ -837,29 +851,71 @@ uint8_t gc_execute_line(char *line)
  if (value_words) { FAIL(STATUS_GCODE_UNUSED_WORDS); } // [Unused words]
  /* -------------------------------------------------------------------------------------
     STEP 3.5ish : EXECUTE JOG!!
     Intercept jog commands and complete error checking for valid jog commands and execute.
     NOTE: G-code parser state is not updated, except the position to ensure sequential jog
     targets are computed correctly. The final parser position after a jog is updated in
     protocol_execute_realtime() when jogging completes or is canceled.
  */
  if (is_jog_motion) {
    // Only distance and unit modal commands and G53 absolute override command are allowed.
    if (command_words & ~(bit(MODAL_GROUP_G3) | bit(MODAL_GROUP_G6 | bit(MODAL_GROUP_G0))) ) { FAIL(STATUS_INVALID_JOG_COMMAND) };
    if (!(gc_block.non_modal_command == NON_MODAL_ABSOLUTE_OVERRIDE || gc_block.non_modal_command == NON_MODAL_NO_ACTION)) { FAIL(STATUS_INVALID_JOG_COMMAND); }
    // NOTE: Feed rate word and axis word checks have already been performed in STEP 3.
    uint8_t status = jog_execute(&gc_block);
    if (status == STATUS_OK) { memcpy(gc_state.position, gc_block.values.xyz, sizeof(gc_block.values.xyz)); }
    return(status);
  }
  /* -------------------------------------------------------------------------------------
     STEP 4: EXECUTE!!
     Assumes that all error-checking has been completed and no failure modes exist. We just
     need to update the state and execute the block according to the order-of-execution.
  */
  // Initialize planner data struct for motion blocks.
  plan_line_data_t plan_data;
  plan_line_data_t *pl_data = &plan_data;
  memset(pl_data,0,sizeof(plan_line_data_t)); // Zero pl_data struct
  // [0. Non-specific/common error-checks and miscellaneous setup]:
  // NOTE: If no line number is present, the value is zero.
  gc_state.line_number = gc_block.values.n;
  #ifdef USE_LINE_NUMBERS
    pl_data->line_number = gc_state.line_number; // Record data for planner use.
  #endif
  // [1. Comments feedback ]:  NOT SUPPORTED
  // [2. Set feed rate mode ]:
  gc_state.modal.feed_rate = gc_block.modal.feed_rate;
  pl_data->condition |= gc_state.modal.feed_rate; // Set condition flag for planner use.
  // [3. Set feed rate ]:
  gc_state.feed_rate = gc_block.values.f; // Always copy this value. See feed rate error-checking.
  pl_data->feed_rate = gc_state.feed_rate; // Record data for planner use.
  // [4. Set spindle speed ]:
  if (gc_state.spindle_speed != gc_block.values.s) {
-    // Update running spindle only if not in check mode and not already enabled.
+    #ifdef VARIABLE_SPINDLE
      if (gc_state.modal.spindle != SPINDLE_DISABLE) {
        if ( bit_istrue(settings.flags, BITFLAG_LASER_MODE) ) {
          // Do not stop motion if in laser mode and a G1, G2, or G3 motion is being executed.
          if (!( (axis_command == AXIS_COMMAND_MOTION_MODE) && ((gc_block.modal.motion == MOTION_MODE_LINEAR ) || (gc_block.modal.motion == MOTION_MODE_CW_ARC) || (gc_block.modal.motion == MOTION_MODE_CCW_ARC)) ) ) {
            spindle_run(gc_state.modal.spindle, gc_block.values.s);
          }
        } else {
          spindle_run(gc_state.modal.spindle, gc_block.values.s);
        }
      }
    #else
      if (gc_state.modal.spindle != SPINDLE_DISABLE) { spindle_run(gc_state.modal.spindle, gc_block.values.s); }
    #endif
    gc_state.spindle_speed = gc_block.values.s;
  }
  pl_data->spindle_speed = gc_state.spindle_speed; // Record data for planner use.
  // [5. Select tool ]: NOT SUPPORTED. Only tracks tool value.
  gc_state.tool = gc_block.values.t;
@ -872,14 +928,19 @@ uint8_t gc_execute_line(char *line)
    spindle_run(gc_block.modal.spindle, gc_state.spindle_speed);
    gc_state.modal.spindle = gc_block.modal.spindle;
  }
  pl_data->condition |= gc_state.modal.spindle; // Set condition flag for planner use.
  // [8. Coolant control ]:
  if (gc_state.modal.coolant != gc_block.modal.coolant) {
    // NOTE: Coolant M-codes are modal. Only one command per line is allowed. But, multiple states
    // can exist at the same time, while coolant disable clears all states.
    coolant_run(gc_block.modal.coolant);
-    gc_state.modal.coolant = gc_block.modal.coolant;
+    if (gc_block.modal.coolant == COOLANT_DISABLE) { gc_state.modal.coolant = COOLANT_DISABLE; }
    else { gc_state.modal.coolant |= gc_block.modal.coolant; }
  }
  pl_data->condition |= gc_state.modal.coolant; // Set condition flag for planner use.
-  // [9. Enable/disable feed rate or spindle overrides ]: NOT SUPPORTED
+  // [9. Enable/disable feed rate or spindle overrides ]: NOT SUPPORTED. Always enabled.
  // [10. Dwell ]:
  if (gc_block.non_modal_command == NON_MODAL_DWELL) { mc_dwell(gc_block.values.p); }
@ -899,17 +960,20 @@ uint8_t gc_execute_line(char *line)
  // axis of the block XYZ value array.
  if (axis_command == AXIS_COMMAND_TOOL_LENGTH_OFFSET ) { // Indicates a change.
    gc_state.modal.tool_length = gc_block.modal.tool_length;
-    if (gc_state.modal.tool_length == TOOL_LENGTH_OFFSET_ENABLE_DYNAMIC) { // G43.1
+    if (gc_state.modal.tool_length == TOOL_LENGTH_OFFSET_CANCEL) { // G49
      gc_block.values.xyz[TOOL_LENGTH_OFFSET_AXIS] = 0.0;
    } // else G43.1
    if ( gc_state.tool_length_offset != gc_block.values.xyz[TOOL_LENGTH_OFFSET_AXIS] ) {
      gc_state.tool_length_offset = gc_block.values.xyz[TOOL_LENGTH_OFFSET_AXIS];
-    } else { // G49
+      system_flag_wco_change();
      gc_state.tool_length_offset = 0.0;
    }
  }
  // [15. Coordinate system selection ]:
  if (gc_state.modal.coord_select != gc_block.modal.coord_select) {
    gc_state.modal.coord_select = gc_block.modal.coord_select;
-    memcpy(gc_state.coord_system,coordinate_data,sizeof(coordinate_data));
+    memcpy(gc_state.coord_system,block_coord_system,N_AXIS*sizeof(float));
    system_flag_wco_change();
  }
  // [16. Set path control mode ]: G61.1/G64 NOT SUPPORTED
@ -923,26 +987,20 @@ uint8_t gc_execute_line(char *line)
  // [19. Go to predefined position, Set G10, or Set axis offsets ]:
  switch(gc_block.non_modal_command) {
    case NON_MODAL_SET_COORDINATE_DATA:
-      settings_write_coord_data(coord_select,parameter_data);
+      settings_write_coord_data(coord_select,gc_block.values.ijk);
      // Update system coordinate system if currently active.
-      if (gc_state.modal.coord_select == coord_select) { memcpy(gc_state.coord_system,parameter_data,sizeof(parameter_data)); }
+      if (gc_state.modal.coord_select == coord_select) {
        memcpy(gc_state.coord_system,gc_block.values.ijk,N_AXIS*sizeof(float));
        system_flag_wco_change();
      }
      break;
    case NON_MODAL_GO_HOME_0: case NON_MODAL_GO_HOME_1:
      // Move to intermediate position before going home. Obeys current coordinate system and offsets
      // and absolute and incremental modes.
-      if (axis_command) {
+      pl_data->condition |= PL_COND_FLAG_RAPID_MOTION; // Set rapid motion condition flag.
-        #ifdef USE_LINE_NUMBERS
+      if (axis_command) { mc_line(gc_block.values.xyz, pl_data); }
-          mc_line(gc_block.values.xyz, -1.0, false, gc_state.line_number);
+      mc_line(gc_block.values.ijk, pl_data);
-        #else
+      memcpy(gc_state.position, gc_block.values.ijk, N_AXIS*sizeof(float));
          mc_line(gc_block.values.xyz, -1.0, false);
        #endif
      }
      #ifdef USE_LINE_NUMBERS
        mc_line(parameter_data, -1.0, false, gc_state.line_number); 
      #else
        mc_line(parameter_data, -1.0, false); 
      #endif
      memcpy(gc_state.position, parameter_data, sizeof(parameter_data));
      break;
    case NON_MODAL_SET_HOME_0:
      settings_write_coord_data(SETTING_INDEX_G28,gc_state.position);
@ -952,9 +1010,11 @@ uint8_t gc_execute_line(char *line)
      break;
    case NON_MODAL_SET_COORDINATE_OFFSET:
      memcpy(gc_state.coord_offset,gc_block.values.xyz,sizeof(gc_block.values.xyz));
      system_flag_wco_change();
      break;
    case NON_MODAL_RESET_COORDINATE_OFFSET:
      clear_vector(gc_state.coord_offset); // Disable G92 offsets by zeroing offset vector.
      system_flag_wco_change();
      break;
  }
@ -965,75 +1025,38 @@ uint8_t gc_execute_line(char *line)
  gc_state.modal.motion = gc_block.modal.motion;
  if (gc_state.modal.motion != MOTION_MODE_NONE) {
    if (axis_command == AXIS_COMMAND_MOTION_MODE) {
-      switch (gc_state.modal.motion) {
+      uint8_t gc_update_pos = GC_UPDATE_POS_TARGET;
-        case MOTION_MODE_SEEK:
+      if (gc_state.modal.motion == MOTION_MODE_LINEAR) {
-          #ifdef USE_LINE_NUMBERS
+        mc_line(gc_block.values.xyz, pl_data);
-            mc_line(gc_block.values.xyz, -1.0, false, gc_state.line_number);
+      } else if (gc_state.modal.motion == MOTION_MODE_SEEK) {
-          #else
+        pl_data->condition |= PL_COND_FLAG_RAPID_MOTION; // Set rapid motion condition flag.
-            mc_line(gc_block.values.xyz, -1.0, false);
+        mc_line(gc_block.values.xyz, pl_data);
-          #endif
+      } else if ((gc_state.modal.motion == MOTION_MODE_CW_ARC) || (gc_state.modal.motion == MOTION_MODE_CCW_ARC)) {
-          break;
+        uint8_t is_clockwise_arc;
-        case MOTION_MODE_LINEAR:
+        if (gc_state.modal.motion == MOTION_MODE_CW_ARC) { is_clockwise_arc = true; }
-          #ifdef USE_LINE_NUMBERS
+        else { is_clockwise_arc = false; }
-            mc_line(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, gc_state.line_number);
+        mc_arc(gc_block.values.xyz, pl_data, gc_state.position, gc_block.values.ijk, gc_block.values.r,
-          #else
+            axis_0, axis_1, axis_linear, is_clockwise_arc);
-            mc_line(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate);
+      } else {
          #endif
          break;
        case MOTION_MODE_CW_ARC: 
          #ifdef USE_LINE_NUMBERS
            mc_arc(gc_state.position, gc_block.values.xyz, gc_block.values.ijk, gc_block.values.r, 
              gc_state.feed_rate, gc_state.modal.feed_rate, axis_0, axis_1, axis_linear, true, gc_state.line_number);  
          #else
            mc_arc(gc_state.position, gc_block.values.xyz, gc_block.values.ijk, gc_block.values.r, 
              gc_state.feed_rate, gc_state.modal.feed_rate, axis_0, axis_1, axis_linear, true); 
          #endif
          break;        
        case MOTION_MODE_CCW_ARC:
          #ifdef USE_LINE_NUMBERS
            mc_arc(gc_state.position, gc_block.values.xyz, gc_block.values.ijk, gc_block.values.r, 
              gc_state.feed_rate, gc_state.modal.feed_rate, axis_0, axis_1, axis_linear, false, gc_state.line_number);  
          #else
            mc_arc(gc_state.position, gc_block.values.xyz, gc_block.values.ijk, gc_block.values.r, 
              gc_state.feed_rate, gc_state.modal.feed_rate, axis_0, axis_1, axis_linear, false); 
          #endif
          break;
        case MOTION_MODE_PROBE_TOWARD: 
        // NOTE: gc_block.values.xyz is returned from mc_probe_cycle with the updated position value. So
        // upon a successful probing cycle, the machine position and the returned value should be the same.
-          #ifdef USE_LINE_NUMBERS
+        uint8_t is_probe_away = false;
-            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, false, false, gc_state.line_number);
+        uint8_t is_no_error = false;
-          #else
+        if ((gc_state.modal.motion == MOTION_MODE_PROBE_AWAY) || (gc_state.modal.motion == MOTION_MODE_PROBE_AWAY_NO_ERROR)) { is_probe_away = true; }
-            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, false, false);
+        if ((gc_state.modal.motion == MOTION_MODE_PROBE_TOWARD_NO_ERROR) || (gc_state.modal.motion == MOTION_MODE_PROBE_AWAY_NO_ERROR)) { is_no_error = true; }
-          #endif
+        gc_update_pos = mc_probe_cycle(gc_block.values.xyz, pl_data, is_probe_away, is_no_error);
          break;
        case MOTION_MODE_PROBE_TOWARD_NO_ERROR:
          #ifdef USE_LINE_NUMBERS
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, false, true, gc_state.line_number);
          #else
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, false, true);
          #endif
          break;
        case MOTION_MODE_PROBE_AWAY:
          #ifdef USE_LINE_NUMBERS
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, true, false, gc_state.line_number);
          #else
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, true, false);
          #endif
          break;
        case MOTION_MODE_PROBE_AWAY_NO_ERROR:
          #ifdef USE_LINE_NUMBERS
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, true, true, gc_state.line_number);
          #else        
            mc_probe_cycle(gc_block.values.xyz, gc_state.feed_rate, gc_state.modal.feed_rate, true, true);
          #endif
    }  
      // As far as the parser is concerned, the position is now == target. In reality the
      // motion control system might still be processing the action and the real tool position
      // in any intermediate location.
      if (gc_update_pos == GC_UPDATE_POS_TARGET) {
        memcpy(gc_state.position, gc_block.values.xyz, sizeof(gc_block.values.xyz)); // gc_state.position[] = gc_block.values.xyz[]
      } else if (gc_update_pos == GC_UPDATE_POS_SYSTEM) {
        gc_sync_position(); // gc_state.position[] = sys_position
      } // == GC_UPDATE_POS_NONE
    }     
  }
  // [21. Program flow ]:
@ -1062,20 +1085,26 @@ uint8_t gc_execute_line(char *line)
      gc_state.modal.coolant = COOLANT_DISABLE;
      // gc_state.modal.override = OVERRIDE_DISABLE; // Not supported.
      #ifdef RESTORE_OVERRIDES_AFTER_PROGRAM_END
        sys.f_override = DEFAULT_FEED_OVERRIDE;
        sys.r_override = DEFAULT_RAPID_OVERRIDE;
        sys.spindle_speed_ovr = DEFAULT_SPINDLE_SPEED_OVERRIDE;
      #endif
      // Execute coordinate change and spindle/coolant stop.
      if (sys.state != STATE_CHECK_MODE) {
-        if (!(settings_read_coord_data(gc_state.modal.coord_select,coordinate_data))) { FAIL(STATUS_SETTING_READ_FAIL); } 
+        if (!(settings_read_coord_data(gc_state.modal.coord_select,gc_state.coord_system))) { FAIL(STATUS_SETTING_READ_FAIL); }
-        memcpy(gc_state.coord_system,coordinate_data,sizeof(coordinate_data));
+        system_flag_wco_change(); // Set to refresh immediately just in case something altered.
        spindle_stop();
-        coolant_stop();		
+        coolant_set_state(COOLANT_DISABLE);
      }
      report_feedback_message(MESSAGE_PROGRAM_END);
    }
    gc_state.modal.program_flow = PROGRAM_FLOW_RUNNING; // Reset program flow.
  }
  // TODO: % to denote start of program.
  return(STATUS_OK);
 }
@ -1099,7 +1128,7 @@ uint8_t gc_execute_line(char *line)
   group 6 = {M6} (Tool change)
   group 7 = {G41, G42} cutter radius compensation (G40 is supported)
   group 8 = {G43} tool length offset (G43.1/G49 are supported)
-   group 8 = {*M7} enable mist coolant (* Compile-option)
+   group 8 = {M7*} enable mist coolant (* Compile-option)
   group 9 = {M48, M49} enable/disable feed and speed override switches
   group 10 = {G98, G99} return mode canned cycles
   group 13 = {G61.1, G64} path control mode (G61 is supported)
--- a/grbl/gcode.h
+++ b/grbl/gcode.h
@ -2,7 +2,7 @@
  gcode.h - rs274/ngc parser.
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -94,7 +94,7 @@
 // Modal Group G5: Feed rate mode
 #define FEED_RATE_MODE_UNITS_PER_MIN  0 // G94 (Default: Must be zero)
-#define FEED_RATE_MODE_INVERSE_TIME 1 // G93
+#define FEED_RATE_MODE_INVERSE_TIME   PL_COND_FLAG_INVERSE_TIME // G93 (NOTE: Uses planner condition bit flag)
 // Modal Group G6: Units mode
 #define UNITS_MODE_MM 0 // G21 (Default: Must be zero)
@ -108,13 +108,13 @@
 // Modal Group M7: Spindle control
 #define SPINDLE_DISABLE 0 // M5 (Default: Must be zero)
-#define SPINDLE_ENABLE_CW 1 // M3
+#define SPINDLE_ENABLE_CW   PL_COND_FLAG_SPINDLE_CW // M3 (NOTE: Uses planner condition bit flag)
-#define SPINDLE_ENABLE_CCW 2 // M4
+#define SPINDLE_ENABLE_CCW  PL_COND_FLAG_SPINDLE_CCW // M4 (NOTE: Uses planner condition bit flag)
 // Modal Group M8: Coolant control
 #define COOLANT_DISABLE 0 // M9 (Default: Must be zero)
-#define COOLANT_MIST_ENABLE 1 // M7
+#define COOLANT_FLOOD_ENABLE  PL_COND_FLAG_COOLANT_FLOOD // M8 (NOTE: Uses planner condition bit flag)
-#define COOLANT_FLOOD_ENABLE 2 // M8
+#define COOLANT_MIST_ENABLE   PL_COND_FLAG_COOLANT_MIST  // M7 (NOTE: Uses planner condition bit flag)
 // Modal Group G8: Tool length offset
 #define TOOL_LENGTH_OFFSET_CANCEL 0 // G49 (Default: Must be zero)
@ -123,7 +123,6 @@
 // Modal Group G12: Active work coordinate system
 // N/A: Stores coordinate system value (54-59) to change to.
 // Define parameter word mapping.
 #define WORD_F  0
 #define WORD_I  1
@ -139,6 +138,23 @@
 #define WORD_Y  11
 #define WORD_Z  12
 // Define g-code parser position updating flags
 #define GC_UPDATE_POS_TARGET   0
 #define GC_UPDATE_POS_SYSTEM   1
 #define GC_UPDATE_POS_NONE     2
 // Define probe cycle exit states and assign proper position updating.
 #define GC_PROBE_FOUND      GC_UPDATE_POS_SYSTEM
 #define GC_PROBE_ABORT      GC_UPDATE_POS_NONE
 #define GC_PROBE_FAIL_INIT  GC_UPDATE_POS_NONE
 #define GC_PROBE_FAIL_END   GC_UPDATE_POS_TARGET
 #ifdef SET_CHECK_MODE_PROBE_TO_START
  #define GC_PROBE_CHECK_MODE   GC_UPDATE_POS_NONE  
 #else
  #define GC_PROBE_CHECK_MODE   GC_UPDATE_POS_TARGET
 #endif
 // NOTE: When this struct is zeroed, the above defines set the defaults for the system.
 typedef struct {
@ -189,16 +205,13 @@ typedef struct {
 } parser_state_t;
 extern parser_state_t gc_state;
 typedef struct {
 //   uint16_t command_words;  // NOTE: If this bitflag variable fills, G and M words can be separated.
 //   uint16_t value_words;
 typedef struct {
  uint8_t non_modal_command;
  gc_modal_t modal;
  gc_values_t values;
 } parser_block_t;
-extern parser_block_t gc_block;
+
 // Initialize the parser
 void gc_init();
--- a/grbl/grbl.h
+++ b/grbl/grbl.h
@ -2,7 +2,7 @@
  grbl.h - main Grbl include file
  Part of Grbl
-  Copyright (c) 2015 Sungeun K. Jeon
+  Copyright (c) 2015-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -22,8 +22,8 @@
 #define grbl_h
 // Grbl versioning system
-#define GRBL_VERSION "1.0c"
+#define GRBL_VERSION "1.1c"
-#define GRBL_VERSION_BUILD "20160330"
+#define GRBL_VERSION_BUILD "20161012"
 // Define standard libraries used by Grbl.
 #include <avr/io.h>
@ -45,6 +45,7 @@
 #include "system.h"
 #include "defaults.h"
 #include "cpu_map.h"
 #include "planner.h"
 #include "coolant_control.h"
 #include "eeprom.h"
 #include "gcode.h"
@ -58,5 +59,6 @@
 #include "serial.h"
 #include "spindle_control.h"
 #include "stepper.h"
 #include "jog.h"
 #endif
--- a/grbl/jog.c
+++ b/grbl/jog.c
@ -0,0 +1,54 @@
 /*
  jog.h - Jogging methods
  Part of Grbl
  Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "grbl.h"
 // Sets up valid jog motion received from g-code parser, checks for soft-limits, and executes the jog.
 uint8_t jog_execute(parser_block_t *gc_block)
 {
  // Initialize planner data struct for motion blocks.
  // NOTE: Spindle and coolant are allowed to fully function with overrides during a jog.
  plan_line_data_t plan_data;
  plan_line_data_t *pl_data = &plan_data;
  memset(pl_data,0,sizeof(plan_line_data_t)); // Zero pl_data struct
  pl_data->feed_rate = gc_block->values.f;
  pl_data->spindle_speed = gc_block->values.s; // Continue current spindle and coolant condition.
  plan_data.condition = (PL_COND_FLAG_NO_FEED_OVERRIDE | gc_block->modal.spindle | gc_block->modal.coolant);
  #ifdef USE_LINE_NUMBERS
    pl_data->line_number = JOG_LINE_NUMBER;
  #endif
  if (bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE)) {
    if (system_check_travel_limits(gc_block->values.xyz)) { return(STATUS_TRAVEL_EXCEEDED); }
  }
  // Valid jog command. Plan, set state, and execute.
  mc_line(gc_block->values.xyz,pl_data);
  if (sys.state == STATE_IDLE) {
    if (plan_get_current_block() != NULL) { // Check if there is a block to execute.
      sys.state = STATE_JOG;
      st_prep_buffer();
      st_wake_up();  // NOTE: Manual start. No state machine required.
    }
  }
  return(STATUS_OK);
 }
--- a/grbl/jog.h
+++ b/grbl/jog.h
@ -0,0 +1,32 @@
 /*
  jog.h - Jogging methods
  Part of Grbl
  Copyright (c) 2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
  Grbl is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  You should have received a copy of the GNU General Public License
  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 */
 #ifndef jog_h
 #define jog_h
 #include "gcode.h"
 // System motion line numbers must be zero.
 #define JOG_LINE_NUMBER 0
 // Sets up valid jog motion received from g-code parser, checks for soft-limits, and executes the jog.
 uint8_t jog_execute(parser_block_t *gc_block);
 #endif
--- a/grbl/limits.c
+++ b/grbl/limits.c
@ -2,7 +2,7 @@
  limits.c - code pertaining to limit-switches and performing the homing cycle
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -88,16 +88,15 @@ uint8_t limits_get_state()
 // limit switch can cause a lot of problems, like false readings and multiple interrupt calls.
 // If a switch is triggered at all, something bad has happened and treat it as such, regardless
 // if a limit switch is being disengaged. It's impossible to reliably tell the state of a
-// bouncing pin without a debouncing method. A simple software debouncing feature may be enabled 
+// bouncing pin because the Arduino microcontroller does not retain any state information when
-// through the config.h file, where an extra timer delays the limit pin read by several milli-
+// detecting a pin change. If we poll the pins in the ISR, you can miss the correct reading if the 
-// seconds to help with, not fix, bouncing switches.
+// switch is bouncing.
 // NOTE: Do not attach an e-stop to the limit pins, because this interrupt is disabled during
 // homing cycles and will not respond correctly. Upon user request or need, there may be a
 // special pinout for an e-stop, but it is generally recommended to just directly connect
 // your e-stop switch to the Arduino reset pin, since it is the most correct way to do this.
-#ifndef ENABLE_SOFTWARE_DEBOUNCE
+ISR(LIMIT_INT_vect) // DEFAULT: Limit pin change interrupt process.
-  ISR(LIMIT_INT_vect) // DEFAULT: Limit pin change interrupt process. 
+{
  {
  // Ignore limit switches if already in an alarm state or in-process of executing an alarm.
  // When in the alarm state, Grbl should have been reset or will force a reset, so any pending
  // moves in the planner and serial buffers are all cleared and newly sent blocks will be
@ -109,32 +108,15 @@ uint8_t limits_get_state()
        // Check limit pin state.
        if (limits_get_state()) {
          mc_reset(); // Initiate system kill.
-            system_set_exec_alarm_flag((EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
+          system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT); // Indicate hard limit critical event
        }
      #else
        mc_reset(); // Initiate system kill.
-          system_set_exec_alarm_flag((EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
+        system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT); // Indicate hard limit critical event
      #endif
    }
  }
-  }  
+}
 #else // OPTIONAL: Software debounce limit pin routine.
  // Upon limit pin change, enable watchdog timer to create a short delay. 
  ISR(LIMIT_INT_vect) { if (!(WDTCSR & (1<<WDIE))) { WDTCSR |= (1<<WDIE); } }
  ISR(WDT_vect) // Watchdog timer ISR
  {
    WDTCSR &= ~(1<<WDIE); // Disable watchdog timer. 
    if (sys.state != STATE_ALARM) {  // Ignore if already in alarm state. 
      if (!(sys_rt_exec_alarm)) {
        // Check limit pin state. 
        if (limits_get_state()) {
          mc_reset(); // Initiate system kill.
          system_set_exec_alarm_flag((EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate hard limit critical event
        }
      }  
    }
  }
 #endif
 // Homes the specified cycle axes, sets the machine position, and performs a pull-off motion after
@ -148,7 +130,16 @@ void limits_go_home(uint8_t cycle_mask)
 {
  if (sys.abort) { return; } // Block if system reset has been issued.
-  // Initialize
+  // Initialize plan data struct for homing motion. Spindle and coolant are disabled.
  plan_line_data_t plan_data;
  plan_line_data_t *pl_data = &plan_data;
  memset(pl_data,0,sizeof(plan_line_data_t));
  pl_data->condition = (PL_COND_FLAG_SYSTEM_MOTION|PL_COND_FLAG_NO_FEED_OVERRIDE);
  #ifdef USE_LINE_NUMBERS
    pl_data->line_number = HOMING_CYCLE_LINE_NUMBER;
  #endif
  // Initialize variables used for homing computations.
  uint8_t n_cycle = (2*N_HOMING_LOCATE_CYCLE+1);
  uint8_t step_pin[N_AXIS];
  float target[N_AXIS];
@ -175,7 +166,7 @@ void limits_go_home(uint8_t cycle_mask)
  uint8_t limit_state, axislock, n_active_axis;
  do {
-    system_convert_array_steps_to_mpos(target,sys.position);
+    system_convert_array_steps_to_mpos(target,sys_position);
    // Initialize and declare variables needed for homing routine.
    axislock = 0;
@ -184,7 +175,20 @@ void limits_go_home(uint8_t cycle_mask)
      // Set target location for active axes and setup computation for homing rate.
      if (bit_istrue(cycle_mask,bit(idx))) {
        n_active_axis++;
-        sys.position[idx] = 0;
+        #ifdef COREXY
          if (idx == X_AXIS) {
            int32_t axis_position = system_convert_corexy_to_y_axis_steps(sys_position);
            sys_position[A_MOTOR] = axis_position;
            sys_position[B_MOTOR] = -axis_position;
          } else if (idx == Y_AXIS) {
            int32_t axis_position = system_convert_corexy_to_x_axis_steps(sys_position);
            sys_position[A_MOTOR] = sys_position[B_MOTOR] = axis_position;
          } else {
            sys_position[Z_AXIS] = 0;
          }
        #else
          sys_position[idx] = 0;
        #endif
        // Set target direction based on cycle mask and homing cycle approach state.
        // NOTE: This happens to compile smaller than any other implementation tried.
        if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
@ -202,15 +206,11 @@ void limits_go_home(uint8_t cycle_mask)
    homing_rate *= sqrt(n_active_axis); // [sqrt(N_AXIS)] Adjust so individual axes all move at homing rate.
    sys.homing_axis_lock = axislock;
    plan_sync_position(); // Sync planner position to current machine position.
    // Perform homing cycle. Planner buffer should be empty, as required to initiate the homing cycle.
-    #ifdef USE_LINE_NUMBERS
+    pl_data->feed_rate = homing_rate; // Set current homing rate.
-      plan_buffer_line(target, homing_rate, false, false, HOMING_CYCLE_LINE_NUMBER); // Bypass mc_line(). Directly plan homing motion.
+    plan_buffer_line(target, pl_data); // Bypass mc_line(). Directly plan homing motion.
    #else
      plan_buffer_line(target, homing_rate, false, false); // Bypass mc_line(). Directly plan homing motion.
    #endif
    sys.step_control = STEP_CONTROL_EXECUTE_SYS_MOTION; // Set to execute homing motion and clear existing flags.
    st_prep_buffer(); // Prep and fill segment buffer from newly planned block.
    st_wake_up(); // Initiate motion
    do {
@ -219,7 +219,14 @@ void limits_go_home(uint8_t cycle_mask)
        limit_state = limits_get_state();
        for (idx=0; idx<N_AXIS; idx++) {
          if (axislock & step_pin[idx]) {
-            if (limit_state & (1 << idx)) { axislock &= ~(step_pin[idx]); }
+            if (limit_state & (1 << idx)) {
              #ifdef COREXY
                if (idx==Z_AXIS) { axislock &= ~(step_pin[Z_AXIS]); }
                else { axislock &= ~(step_pin[A_MOTOR]|step_pin[B_MOTOR]); }
              #else
                axislock &= ~(step_pin[idx]);
              #endif
            }
          }
        }
        sys.homing_axis_lock = axislock;
@ -229,10 +236,16 @@ void limits_go_home(uint8_t cycle_mask)
      // Exit routines: No time to run protocol_execute_realtime() in this loop.
      if (sys_rt_exec_state & (EXEC_SAFETY_DOOR | EXEC_RESET | EXEC_CYCLE_STOP)) {
-        // Homing failure: Limit switches are still engaged after pull-off motion
+        uint8_t rt_exec = sys_rt_exec_state;
-        if ( (sys_rt_exec_state & (EXEC_SAFETY_DOOR | EXEC_RESET)) ||  // Safety door or reset issued
+        // Homing failure condition: Reset issued during cycle.
-           (!approach && (limits_get_state() & cycle_mask)) ||  // Limit switch still engaged after pull-off motion
+        if (rt_exec & EXEC_RESET) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_RESET); }
-           ( approach && (sys_rt_exec_state & EXEC_CYCLE_STOP)) ) { // Limit switch not found during approach.
+        // Homing failure condition: Safety door was opened.
        if (rt_exec & EXEC_SAFETY_DOOR) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_DOOR); }
        // Homing failure condition: Limit switch still engaged after pull-off motion
        if (!approach && (limits_get_state() & cycle_mask)) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_PULLOFF); }
        // Homing failure condition: Limit switch not found during approach.
        if (approach && (rt_exec & EXEC_CYCLE_STOP)) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_APPROACH); }
        if (sys_rt_exec_alarm) {
          mc_reset(); // Stop motors, if they are running.
          protocol_execute_realtime();
          return;
@ -246,8 +259,6 @@ void limits_go_home(uint8_t cycle_mask)
    } while (STEP_MASK & axislock);
    st_reset(); // Immediately force kill steppers and reset step segment buffer.
    plan_reset(); // Reset planner buffer to zero planner current position and to clear previous motions.
    delay_ms(settings.homing_debounce_delay); // Delay to allow transient dynamics to dissipate.
    // Reverse direction and reset homing rate for locate cycle(s).
@ -270,9 +281,6 @@ void limits_go_home(uint8_t cycle_mask)
  // set up pull-off maneuver from axes limit switches that have been homed. This provides
  // some initial clearance off the switches and should also help prevent them from falsely
  // triggering when hard limits are enabled or when more than one axes shares a limit pin.
  #ifdef COREXY
    int32_t off_axis_position = 0;
  #endif
  int32_t set_axis_position;
  // Set machine positions for homed limit switches. Don't update non-homed axes.
  for (idx=0; idx<N_AXIS; idx++) {
@ -290,49 +298,33 @@ void limits_go_home(uint8_t cycle_mask)
      #ifdef COREXY
        if (idx==X_AXIS) {
-          off_axis_position = (sys.position[B_MOTOR] - sys.position[A_MOTOR])/2;
+          int32_t off_axis_position = system_convert_corexy_to_y_axis_steps(sys_position);
-          sys.position[A_MOTOR] = set_axis_position - off_axis_position;
+          sys_position[A_MOTOR] = set_axis_position + off_axis_position;
-          sys.position[B_MOTOR] = set_axis_position + off_axis_position;          
+          sys_position[B_MOTOR] = set_axis_position - off_axis_position;
        } else if (idx==Y_AXIS) {
-          off_axis_position = (sys.position[A_MOTOR] + sys.position[B_MOTOR])/2;
+          int32_t off_axis_position = system_convert_corexy_to_x_axis_steps(sys_position);
-          sys.position[A_MOTOR] = off_axis_position - set_axis_position;
+          sys_position[A_MOTOR] = off_axis_position + set_axis_position;
-          sys.position[B_MOTOR] = off_axis_position + set_axis_position;
+          sys_position[B_MOTOR] = off_axis_position - set_axis_position;
        } else {
-          sys.position[idx] = set_axis_position;
+          sys_position[idx] = set_axis_position;
        }
      #else
-        sys.position[idx] = set_axis_position;
+        sys_position[idx] = set_axis_position;
      #endif
    }
  }
-  plan_sync_position(); // Sync planner position to homed machine position.
+  sys.step_control = STEP_CONTROL_NORMAL_OP; // Return step control to normal operation.
  // sys.state = STATE_HOMING; // Ensure system state set as homing before returning. 
 }
 // Performs a soft limit check. Called from mc_line() only. Assumes the machine has been homed,
 // the workspace volume is in all negative space, and the system is in normal operation.
 // NOTE: Used by jogging to limit travel within soft-limit volume.
 void limits_soft_check(float *target)
 {
-  uint8_t idx;
+  if (system_check_travel_limits(target)) {
-  for (idx=0; idx<N_AXIS; idx++) {
+    sys.soft_limit = true;
    #ifdef HOMING_FORCE_SET_ORIGIN
      // When homing forced set origin is enabled, soft limits checks need to account for directionality.
      // NOTE: max_travel is stored as negative
      if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
        if (target[idx] < 0 || target[idx] > -settings.max_travel[idx]) { sys.soft_limit = true; }
      } else {
        if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { sys.soft_limit = true; }
      }
    #else  
      // NOTE: max_travel is stored as negative
      if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { sys.soft_limit = true; }
    #endif
    if (sys.soft_limit) {
    // Force feed hold if cycle is active. All buffered blocks are guaranteed to be within
    // workspace volume so just come to a controlled stop so position is not lost. When complete
    // enter alarm mode.
@ -343,11 +335,9 @@ void limits_soft_check(float *target)
        if (sys.abort) { return; }
      } while ( sys.state != STATE_IDLE );
    }
    mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
-      system_set_exec_alarm_flag((EXEC_ALARM_SOFT_LIMIT|EXEC_CRITICAL_EVENT)); // Indicate soft limit critical event
+    system_set_exec_alarm(EXEC_ALARM_SOFT_LIMIT); // Indicate soft limit critical event
    protocol_execute_realtime(); // Execute to enter critical event loop and system abort
    return;
  }
  }
 }
--- a/grbl/limits.h
+++ b/grbl/limits.h
@ -2,7 +2,7 @@
  limits.h - code pertaining to limit-switches and performing the homing cycle
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon  
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
--- a/grbl/main.c
+++ b/grbl/main.c
@ -2,7 +2,7 @@
  main.c - An embedded CNC Controller with rs274/ngc (g-code) support
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -76,11 +76,23 @@ int main(void)
    gc_sync_position();
    // Reset system variables.
-    sys.abort = false;
+    sys.abort = sys.suspend = sys.soft_limit = false;
    sys.step_control = STEP_CONTROL_NORMAL_OP;
    sys.f_override = DEFAULT_FEED_OVERRIDE;
    sys.r_override = DEFAULT_RAPID_OVERRIDE;
    sys.spindle_speed_ovr = DEFAULT_SPINDLE_SPEED_OVERRIDE;
    sys.toggle_ovr_mask = 0;
    sys.report_wco_counter = REPORT_WCO_REFRESH_BUSY_COUNT; // Set to include in first report.
    sys.report_ovr_counter = REPORT_OVR_REFRESH_BUSY_COUNT; // Set to include in first report.
    sys_probe_state = 0;
    sys_rt_exec_state = 0;
    sys_rt_exec_alarm = 0;
-    sys.suspend = false;
+    sys_rt_exec_motion_override = 0;
-    sys.soft_limit = false;
+    sys_rt_exec_accessory_override = 0;
    // Print welcome message. Indicates an initialization has occured at power-up or with a reset.
    report_init_message();
    // Start Grbl main loop. Processes program inputs and executes them.
    protocol_main_loop();
--- a/grbl/motion_control.c
+++ b/grbl/motion_control.c
@ -2,9 +2,8 @@
  motion_control.c - high level interface for issuing motion commands
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Copyright (c) 2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -30,15 +29,14 @@
 // segments, must pass through this routine before being passed to the planner. The seperation of
 // mc_line and plan_buffer_line is done primarily to place non-planner-type functions from being
 // in the planner and to let backlash compensation or canned cycle integration simple and direct.
-#ifdef USE_LINE_NUMBERS
+void mc_line(float *target, plan_line_data_t *pl_data)
  void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate, int32_t line_number)
 #else
  void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate)
 #endif
 {
  // If enabled, check for soft limit violations. Placed here all line motions are picked up
  // from everywhere in Grbl.
-  if (bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE)) { limits_soft_check(target); }    
+  if (bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE)) {
    // NOTE: Block jog state. Jogging is a special case and soft limits are handled independently.
    if (sys.state != STATE_JOG) { limits_soft_check(target); }
  }
  // If in check gcode mode, prevent motion by blocking planner. Soft limits still work.
  if (sys.state == STATE_CHECK_MODE) { return; }
@ -68,11 +66,7 @@
  // Plan and queue motion into planner buffer
  // uint8_t plan_status; // Not used in normal operation.
-  #ifdef USE_LINE_NUMBERS
+  plan_buffer_line(target, pl_data);
    plan_buffer_line(target, feed_rate, invert_feed_rate, false, line_number);
  #else
    plan_buffer_line(target, feed_rate, invert_feed_rate, false);
  #endif
 }
@ -83,13 +77,8 @@
 // The arc is approximated by generating a huge number of tiny, linear segments. The chordal tolerance
 // of each segment is configured in settings.arc_tolerance, which is defined to be the maximum normal
 // distance from segment to the circle when the end points both lie on the circle.
-#ifdef USE_LINE_NUMBERS
+void mc_arc(float *target, plan_line_data_t *pl_data, float *position, float *offset, float radius,
-  void mc_arc(float *position, float *target, float *offset, float radius, float feed_rate, 
+  uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc)
    uint8_t invert_feed_rate, uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc, int32_t line_number)
 #else
  void mc_arc(float *position, float *target, float *offset, float radius, float feed_rate,
    uint8_t invert_feed_rate, uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc)
 #endif
 {
  float center_axis0 = position[axis_0] + offset[axis_0];
  float center_axis1 = position[axis_1] + offset[axis_1];
@ -117,7 +106,7 @@
    // Multiply inverse feed_rate to compensate for the fact that this movement is approximated
    // by a number of discrete segments. The inverse feed_rate should be correct for the sum of
    // all segments.
-    if (invert_feed_rate) { feed_rate *= segments; }
+    if (pl_data->condition & PL_COND_FLAG_INVERSE_TIME) { pl_data->feed_rate *= segments; }
    float theta_per_segment = angular_travel/segments;
    float linear_per_segment = (target[axis_linear] - position[axis_linear])/segments;
@ -181,22 +170,14 @@
      position[axis_1] = center_axis1 + r_axis1;
      position[axis_linear] += linear_per_segment;
-      #ifdef USE_LINE_NUMBERS
+      mc_line(position, pl_data);
        mc_line(position, feed_rate, invert_feed_rate, line_number);
      #else
        mc_line(position, feed_rate, invert_feed_rate);
      #endif
      // Bail mid-circle on system abort. Runtime command check already performed by mc_line.
      if (sys.abort) { return; }
    }
  }
  // Ensure last segment arrives at target location.
-  #ifdef USE_LINE_NUMBERS
+  mc_line(target, pl_data);
    mc_line(target, feed_rate, invert_feed_rate, line_number);
  #else
    mc_line(target, feed_rate, invert_feed_rate);
  #endif
 }
@ -220,7 +201,7 @@ void mc_homing_cycle()
  #ifdef LIMITS_TWO_SWITCHES_ON_AXES
    if (limits_get_state()) {
      mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
-      system_set_exec_alarm_flag((EXEC_ALARM_HARD_LIMIT|EXEC_CRITICAL_EVENT));
+      system_set_exec_alarm(EXEC_ALARM_HARD_LIMIT);
      return;
    }
  #endif
@ -245,8 +226,9 @@ void mc_homing_cycle()
  // Homing cycle complete! Setup system for normal operation.
  // -------------------------------------------------------------------------------------
-  // Gcode parser position was circumvented by the limits_go_home() routine, so sync position now.
+  // Sync gcode parser and planner positions to homed position.
  gc_sync_position();
  plan_sync_position();
  // If hard limits feature enabled, re-enable hard limits pin change register after homing cycle.
  limits_init();
@ -255,19 +237,14 @@ void mc_homing_cycle()
 // Perform tool length probe cycle. Requires probe switch.
 // NOTE: Upon probe failure, the program will be stopped and placed into ALARM state.
-#ifdef USE_LINE_NUMBERS
+uint8_t mc_probe_cycle(float *target, plan_line_data_t *pl_data, uint8_t is_probe_away, uint8_t is_no_error)
  void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_probe_away, 
    uint8_t is_no_error, int32_t line_number)
 #else
  void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_probe_away,
    uint8_t is_no_error)
 #endif
 {
  // TODO: Need to update this cycle so it obeys a non-auto cycle start.
-  if (sys.state == STATE_CHECK_MODE) { return; }
+  if (sys.state == STATE_CHECK_MODE) { return(GC_PROBE_CHECK_MODE); }
  // Finish all queued commands and empty planner buffer before starting probe cycle.
  protocol_buffer_synchronize();
  if (sys.abort) { return(GC_PROBE_ABORT); } // Return if system reset has been issued.
  // Initialize probing control variables
  sys.probe_succeeded = false; // Re-initialize probe history before beginning cycle.
@ -276,17 +253,14 @@ void mc_homing_cycle()
  // After syncing, check if probe is already triggered. If so, halt and issue alarm.
  // NOTE: This probe initialization error applies to all probing cycles.
  if ( probe_get_state() ) { // Check probe pin state.
-    system_set_exec_alarm_flag(EXEC_ALARM_PROBE_FAIL);
+    system_set_exec_alarm(EXEC_ALARM_PROBE_FAIL_INITIAL);
    protocol_execute_realtime();
    probe_configure_invert_mask(false); // Re-initialize invert mask before returning.
    return(GC_PROBE_FAIL_INIT); // Nothing else to do but bail.
  }
  if (sys.abort) { return; } // Return if system reset has been issued.
  // Setup and queue probing motion. Auto cycle-start should not start the cycle.
-  #ifdef USE_LINE_NUMBERS
+  mc_line(target, pl_data);
    mc_line(target, feed_rate, invert_feed_rate, line_number);
  #else
    mc_line(target, feed_rate, invert_feed_rate);
  #endif
  // Activate the probing state monitor in the stepper module.
  sys_probe_state = PROBE_ACTIVE;
@ -295,51 +269,47 @@ void mc_homing_cycle()
  system_set_exec_state_flag(EXEC_CYCLE_START);
  do {
    protocol_execute_realtime();
-    if (sys.abort) { return; } // Check for system abort
+    if (sys.abort) { return(GC_PROBE_ABORT); } // Check for system abort
  } while (sys.state != STATE_IDLE);
  // Probing cycle complete!
  // Set state variables and error out, if the probe failed and cycle with error is enabled.
  if (sys_probe_state == PROBE_ACTIVE) {
-    if (is_no_error) { memcpy(sys.probe_position, sys.position, sizeof(sys.position)); }
+    if (is_no_error) { memcpy(sys_probe_position, sys_position, sizeof(sys_position)); }
-    else { system_set_exec_alarm_flag(EXEC_ALARM_PROBE_FAIL); }
+    else { system_set_exec_alarm(EXEC_ALARM_PROBE_FAIL_CONTACT); }
  } else {
    sys.probe_succeeded = true; // Indicate to system the probing cycle completed successfully.
  }
  sys_probe_state = PROBE_OFF; // Ensure probe state monitor is disabled.
  probe_configure_invert_mask(false); // Re-initialize invert mask.
  protocol_execute_realtime();   // Check and execute run-time commands
  if (sys.abort) { return; } // Check for system abort
  // Reset the stepper and planner buffers to remove the remainder of the probe motion.
-  st_reset(); // Reest step segment buffer.
+  st_reset(); // Reset step segment buffer.
  plan_reset(); // Reset planner buffer. Zero planner positions. Ensure probing motion is cleared.
  plan_sync_position(); // Sync planner position to current machine position.
  // TODO: Update the g-code parser code to not require this target calculation but uses a gc_sync_position() call.
  // NOTE: The target[] variable updated here will be sent back and synced with the g-code parser.
  system_convert_array_steps_to_mpos(target, sys.position);
  #ifdef MESSAGE_PROBE_COORDINATES
    // All done! Output the probe position as message.
    report_probe_parameters();
  #endif
  if (sys.probe_succeeded) { return(GC_PROBE_FOUND); } // Successful probe cycle.
  else { return(GC_PROBE_FAIL_END); } // Failed to trigger probe within travel. With or without error.
 }
 // Plans and executes the single special motion case for parking. Independent of main planner buffer.
 // NOTE: Uses the always free planner ring buffer head to store motion parameters for execution.
-void mc_parking_motion(float *parking_target, float feed_rate) 
+void mc_parking_motion(float *parking_target, plan_line_data_t *pl_data)
 {
  if (sys.abort) { return; } // Block during abort.
-  #ifdef USE_LINE_NUMBERS
+  uint8_t plan_status = plan_buffer_line(parking_target, pl_data);
-    uint8_t plan_status = plan_buffer_line(parking_target, feed_rate, false, true, PARKING_MOTION_LINE_NUMBER);
+
  #else
    uint8_t plan_status = plan_buffer_line(parking_target, feed_rate, false, true);
  #endif
  if (plan_status) {
-		bit_true(sys.step_control, STEP_CONTROL_EXECUTE_PARK); 
+		bit_true(sys.step_control, STEP_CONTROL_EXECUTE_SYS_MOTION);
 		bit_false(sys.step_control, STEP_CONTROL_END_MOTION); // Allow parking motion to execute, if feed hold is active.
    st_parking_setup_buffer(); // Setup step segment buffer for special parking motion case
 		st_prep_buffer();
@ -347,10 +317,10 @@ void mc_parking_motion(float *parking_target, float feed_rate)
 		do {
 			protocol_exec_rt_system();
 			if (sys.abort) { return; }
-		} while (sys.step_control & STEP_CONTROL_EXECUTE_PARK);  
+		} while (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION);
 		st_parking_restore_buffer(); // Restore step segment buffer to normal run state.
 	} else {
-    bit_false(sys.step_control, STEP_CONTROL_EXECUTE_PARK);
+    bit_false(sys.step_control, STEP_CONTROL_EXECUTE_SYS_MOTION);
 		protocol_exec_rt_system();
  }
@ -370,16 +340,16 @@ void mc_reset()
    // Kill spindle and coolant.
    spindle_stop();
-    coolant_stop();
+    coolant_set_state(COOLANT_DISABLE);
    // Kill steppers only if in any motion state, i.e. cycle, actively holding, or homing.
    // NOTE: If steppers are kept enabled via the step idle delay setting, this also keeps
    // the steppers enabled by avoiding the go_idle call altogether, unless the motion state is
    // violated, by which, all bets are off.
-    if ((sys.state & (STATE_CYCLE | STATE_HOMING)) || 
+    if ((sys.state & (STATE_CYCLE | STATE_HOMING | STATE_JOG)) ||
-    		(sys.step_control & (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_PARK))) {
+    		(sys.step_control & (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_SYS_MOTION))) {
-      if (sys.state == STATE_HOMING) { system_set_exec_alarm_flag(EXEC_ALARM_HOMING_FAIL); }
+      if (sys.state == STATE_HOMING) { system_set_exec_alarm(EXEC_ALARM_HOMING_FAIL_RESET); }
-      else { system_set_exec_alarm_flag(EXEC_ALARM_ABORT_CYCLE); }
+      else { system_set_exec_alarm(EXEC_ALARM_ABORT_CYCLE); }
      st_go_idle(); // Force kill steppers. Position has likely been lost.
    }
  }
--- a/grbl/motion_control.h
+++ b/grbl/motion_control.h
@ -2,7 +2,7 @@
  motion_control.h - high level interface for issuing motion commands
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -23,29 +23,21 @@
 #define motion_control_h
-#define HOMING_CYCLE_LINE_NUMBER -1
+// System motion commands must have a line number of zero.
-#define PARKING_MOTION_LINE_NUMBER -2
+#define HOMING_CYCLE_LINE_NUMBER 0
 #define PARKING_MOTION_LINE_NUMBER 0
 // Execute linear motion in absolute millimeter coordinates. Feed rate given in millimeters/second
 // unless invert_feed_rate is true. Then the feed_rate means that the motion should be completed in
 // (1 minute)/feed_rate time.
-#ifdef USE_LINE_NUMBERS
+void mc_line(float *target, plan_line_data_t *pl_data);
 void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate, int32_t line_number);
 #else
 void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate);
 #endif
 // Execute an arc in offset mode format. position == current xyz, target == target xyz,
 // offset == offset from current xyz, axis_XXX defines circle plane in tool space, axis_linear is
 // the direction of helical travel, radius == circle radius, is_clockwise_arc boolean. Used
 // for vector transformation direction.
-#ifdef USE_LINE_NUMBERS
+void mc_arc(float *target, plan_line_data_t *pl_data, float *position, float *offset, float radius,
-void mc_arc(float *position, float *target, float *offset, float radius, float feed_rate, 
+  uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc);
  uint8_t invert_feed_rate, uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc, int32_t line_number);
 #else
 void mc_arc(float *position, float *target, float *offset, float radius, float feed_rate,
  uint8_t invert_feed_rate, uint8_t axis_0, uint8_t axis_1, uint8_t axis_linear, uint8_t is_clockwise_arc);
 #endif
 // Dwell for a specific number of seconds
 void mc_dwell(float seconds);
@ -54,16 +46,10 @@ void mc_dwell(float seconds);
 void mc_homing_cycle();
 // Perform tool length probe cycle. Requires probe switch.
-#ifdef USE_LINE_NUMBERS
+uint8_t mc_probe_cycle(float *target, plan_line_data_t *pl_data, uint8_t is_probe_away, uint8_t is_no_error);
 void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_probe_away,
  uint8_t is_no_error, int32_t line_number);
 #else
 void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_probe_away,
  uint8_t is_no_error);
 #endif
 // Plans and executes the single special motion case for parking. Independent of main planner buffer.
-void mc_parking_motion(float *parking_target, float feed_rate);
+void mc_parking_motion(float *parking_target, plan_line_data_t *pl_data);
 // Performs system reset. If in motion state, kills all motion and sets system alarm.
 void mc_reset();
--- a/grbl/nuts_bolts.c
+++ b/grbl/nuts_bolts.c
@ -2,7 +2,7 @@
  nuts_bolts.c - Shared functions
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -116,7 +116,7 @@ void delay_sec(float seconds, uint8_t mode)
 		if (sys.abort) { return; }
 		if (mode == DELAY_MODE_DWELL) {
 			protocol_execute_realtime();
-		} else { // DELAY_MODE_SAFETY_DOOR
+		} else { // DELAY_MODE_SYS_SUSPEND
 		  // Execute rt_system() only to avoid nesting suspend loops.
 		  protocol_exec_rt_system();
 		  if (sys.suspend & SUSPEND_RESTART_RETRACT) { return; } // Bail, if safety door reopens.
@ -159,3 +159,32 @@ void delay_us(uint32_t us)
 // Simple hypotenuse computation function.
 float hypot_f(float x, float y) { return(sqrt(x*x + y*y)); }
 float convert_delta_vector_to_unit_vector(float *vector)
 {
  uint8_t idx;
  float magnitude = 0.0;
  for (idx=0; idx<N_AXIS; idx++) {
    if (vector[idx] != 0.0) {
      magnitude += vector[idx]*vector[idx];
    }
  }
  magnitude = sqrt(magnitude);
  float inv_magnitude = 1.0/magnitude;
  for (idx=0; idx<N_AXIS; idx++) { vector[idx] *= inv_magnitude; }
  return(magnitude);
 }
 float limit_value_by_axis_maximum(float *max_value, float *unit_vec)
 {
  uint8_t idx;
  float limit_value = SOME_LARGE_VALUE;
  for (idx=0; idx<N_AXIS; idx++) {
    if (unit_vec[idx] != 0) {  // Avoid divide by zero.
      limit_value = min(limit_value,fabs(max_value[idx]/unit_vec[idx]));
    }
  }
  return(limit_value);
 }
--- a/grbl/nuts_bolts.h
+++ b/grbl/nuts_bolts.h
@ -2,7 +2,7 @@
  nuts_bolts.h - Header file for shared definitions, variables, and functions
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon 
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -25,6 +25,8 @@
 #define false 0
 #define true 1
 #define SOME_LARGE_VALUE 1.0E+38
 // Axis array index values. Must start with 0 and be continuous.
 #define N_AXIS 3 // Number of axes
 #define X_AXIS 0 // Axis indexing value.
@ -45,7 +47,7 @@
 #define TICKS_PER_MICROSECOND (F_CPU/1000000)
 #define DELAY_MODE_DWELL       0
-#define DELAY_MODE_SAFETY_DOOR 1
+#define DELAY_MODE_SYS_SUSPEND 1
 // Useful macros
 #define clear_vector(a) memset(a, 0, sizeof(a))
@ -53,6 +55,7 @@
 // #define clear_vector_long(a) memset(a, 0.0, sizeof(long)*N_AXIS)
 #define max(a,b) (((a) > (b)) ? (a) : (b))
 #define min(a,b) (((a) < (b)) ? (a) : (b))
 #define isequal_position_vector(a,b) !(memcmp(a, b, sizeof(float)*N_AXIS))
 // Bit field and masking macros
 #define bit(n) (1 << n)
@ -78,4 +81,7 @@ void delay_us(uint32_t us);
 // Computes hypotenuse, avoiding avr-gcc's bloated version and the extra error checking.
 float hypot_f(float x, float y);
 float convert_delta_vector_to_unit_vector(float *vector);
 float limit_value_by_axis_maximum(float *max_value, float *unit_vec);
 #endif
--- a/grbl/planner.c
+++ b/grbl/planner.c
@ -2,7 +2,7 @@
  planner.c - buffers movement commands and manages the acceleration profile plan
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Copyright (c) 2011 Jens Geisler
@ -22,8 +22,6 @@
 #include "grbl.h"
 #define SOME_LARGE_VALUE 1.0E+38 // Used by rapids and acceleration maximization calculations. Just needs
                                 // to be larger than any feasible (mm/min)^2 or mm/sec^2 value.
 static plan_block_t block_buffer[BLOCK_BUFFER_SIZE];  // A ring buffer for motion instructions
 static uint8_t block_buffer_tail;     // Index of the block to process now
@ -37,7 +35,7 @@ typedef struct {
                                     // from g-code position for movements requiring multiple line motions,
                                     // i.e. arcs, canned cycles, and backlash compensation.
  float previous_unit_vec[N_AXIS];   // Unit vector of previous path line segment
-  float previous_nominal_speed_sqr;  // Nominal speed of previous path line segment
+  float previous_nominal_speed;  // Nominal speed of previous path line segment
 } planner_t;
 static planner_t pl;
@ -201,6 +199,12 @@ static void planner_recalculate()
 void plan_reset()
 {
  memset(&pl, 0, sizeof(planner_t)); // Clear planner struct
  plan_reset_buffer();
 }
 void plan_reset_buffer()
 {
  block_buffer_tail = 0;
  block_buffer_head = 0; // Empty = tail
  next_buffer_head = 1; // plan_next_block_index(block_buffer_head)
@ -219,12 +223,14 @@ void plan_discard_current_block()
 }
-plan_block_t *plan_get_parking_block()
+// Returns address of planner buffer block used by system motions. Called by segment generator.
 plan_block_t *plan_get_system_motion_block()
 {
  return(&block_buffer[block_buffer_head]);
 }
 // Returns address of first planner block, if available. Called by various main program functions.
 plan_block_t *plan_get_current_block()
 {
  if (block_buffer_head == block_buffer_tail) { return(NULL); } // Buffer empty
@ -232,11 +238,11 @@ plan_block_t *plan_get_current_block()
 }
-float plan_get_exec_block_exit_speed()
+float plan_get_exec_block_exit_speed_sqr()
 {
  uint8_t block_index = plan_next_block_index(block_buffer_tail);
  if (block_index == block_buffer_head) { return( 0.0 ); }
-  return( sqrt( block_buffer[block_index].entry_speed_sqr ) ); 
+  return( block_buffer[block_index].entry_speed_sqr );
 }
@ -248,6 +254,53 @@ uint8_t plan_check_full_buffer()
 }
 // Computes and returns block nominal speed based on running condition and override values.
 // NOTE: All system motion commands, such as homing/parking, are not subject to overrides.
 float plan_compute_profile_nominal_speed(plan_block_t *block)
 {
  float nominal_speed;
  if (block->condition & PL_COND_FLAG_RAPID_MOTION) {
    nominal_speed = block->rapid_rate;
    nominal_speed *= (0.01*sys.r_override);
  } else {
    nominal_speed = block->programmed_rate;
    if (!(block->condition & PL_COND_FLAG_NO_FEED_OVERRIDE)) { nominal_speed *= (0.01*sys.f_override); }
    if (nominal_speed > block->rapid_rate) { nominal_speed = block->rapid_rate; }
  }
  if (nominal_speed > MINIMUM_FEED_RATE) { return(nominal_speed); }
  return(MINIMUM_FEED_RATE);
 }
 // Computes and updates the max entry speed (sqr) of the block, based on the minimum of the junction's
 // previous and current nominal speeds and max junction speed.
 static void plan_compute_profile_parameters(plan_block_t *block, float nominal_speed, float prev_nominal_speed)
 {
  // Compute the junction maximum entry based on the minimum of the junction speed and neighboring nominal speeds.
  if (nominal_speed > prev_nominal_speed) { block->max_entry_speed_sqr = prev_nominal_speed*prev_nominal_speed; }
  else { block->max_entry_speed_sqr = nominal_speed*nominal_speed; }
  if (block->max_entry_speed_sqr > block->max_junction_speed_sqr) { block->max_entry_speed_sqr = block->max_junction_speed_sqr; }
 }
 // Re-calculates buffered motions profile parameters upon a motion-based override change.
 void plan_update_velocity_profile_parameters()
 {
  uint8_t block_index = block_buffer_tail;
  plan_block_t *block;
  float nominal_speed;
  float prev_nominal_speed = SOME_LARGE_VALUE; // Set high for first block nominal speed calculation.
  while (block_index != block_buffer_head) {
    block = &block_buffer[block_index];
    nominal_speed = plan_compute_profile_nominal_speed(block);
    plan_compute_profile_parameters(block, nominal_speed, prev_nominal_speed);
    prev_nominal_speed = nominal_speed;
    block_index = plan_next_block_index(block_index);
  }
  pl.previous_nominal_speed = prev_nominal_speed; // Update prev nominal speed for next incoming block.
 }
 /* Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position
   in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
   rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
@ -258,35 +311,30 @@ uint8_t plan_check_full_buffer()
   is used in three ways: as a normal feed rate if invert_feed_rate is false, as inverse time if
   invert_feed_rate is true, or as seek/rapids rate if the feed_rate value is negative (and
   invert_feed_rate always false).
-   The is_parking_motion boolean tells the planner to plan a motion in the always unused block buffer
+   The system motion condition tells the planner to plan a motion in the always unused block buffer
   head. It avoids changing the planner state and preserves the buffer to ensure subsequent gcode
   motions are still planned correctly, while the stepper module only points to the block buffer head
-   to execute the parking motion. */
+   to execute the special system motion. */
-#ifdef USE_LINE_NUMBERS   
+uint8_t plan_buffer_line(float *target, plan_line_data_t *pl_data)
  uint8_t plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_parking_motion, int32_t line_number) 
 #else
  uint8_t plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_parking_motion) 
 #endif
 {
-  // Prepare and initialize new block
+  // Prepare and initialize new block. Copy relevant pl_data for block execution.
  plan_block_t *block = &block_buffer[block_buffer_head];
-  block->step_event_count = 0;
+  memset(block,0,sizeof(plan_block_t)); // Zero all block values.
-  block->millimeters = 0;
+  block->condition = pl_data->condition;
-  block->direction_bits = 0;
+  #ifdef VARIABLE_SPINDLE
-  block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
+    block->spindle_speed = pl_data->spindle_speed;
  #endif
  #ifdef USE_LINE_NUMBERS
-    block->line_number = line_number;
+    block->line_number = pl_data->line_number;
  #endif
  // Compute and store initial move distance data.
  // TODO: After this for-loop, we don't touch the stepper algorithm data. Might be a good idea
  // to try to keep these types of things completely separate from the planner for portability.
  int32_t target_steps[N_AXIS], position_steps[N_AXIS];
  float unit_vec[N_AXIS], delta_mm;
  uint8_t idx;
  // Copy position data based on type of motion being planned.
-  if (is_parking_motion) { memcpy(position_steps, sys.position, sizeof(sys.position)); }
+  if (block->condition & PL_COND_FLAG_SYSTEM_MOTION) { memcpy(position_steps, sys_position, sizeof(sys_position)); }
  else { memcpy(position_steps, pl.position, sizeof(pl.position)); }
  #ifdef COREXY
@ -307,9 +355,9 @@ uint8_t plan_check_full_buffer()
      }
      block->step_event_count = max(block->step_event_count, block->steps[idx]);
      if (idx == A_MOTOR) {
-        delta_mm = ((target_steps[X_AXIS]-position_steps[X_AXIS]) + (target_steps[Y_AXIS]-position_steps[Y_AXIS]))/settings.steps_per_mm[idx];
+        delta_mm = (target_steps[X_AXIS]-position_steps[X_AXIS] + target_steps[Y_AXIS]-position_steps[Y_AXIS])/settings.steps_per_mm[idx];
      } else if (idx == B_MOTOR) {
-        delta_mm = ((target_steps[X_AXIS]-position_steps[X_AXIS]) - (target_steps[Y_AXIS]-position_steps[Y_AXIS]))/settings.steps_per_mm[idx];
+        delta_mm = (target_steps[X_AXIS]-position_steps[X_AXIS] - target_steps[Y_AXIS]+position_steps[Y_AXIS])/settings.steps_per_mm[idx];
      } else {
        delta_mm = (target_steps[idx] - position_steps[idx])/settings.steps_per_mm[idx];
      }
@ -319,110 +367,91 @@ uint8_t plan_check_full_buffer()
      block->step_event_count = max(block->step_event_count, block->steps[idx]);
      delta_mm = (target_steps[idx] - position_steps[idx])/settings.steps_per_mm[idx];
 	  #endif
-    unit_vec[idx] = delta_mm; // Store unit vector numerator. Denominator computed later.
+    unit_vec[idx] = delta_mm; // Store unit vector numerator
    // Set direction bits. Bit enabled always means direction is negative.
-    if (delta_mm < 0 ) { block->direction_bits |= get_direction_pin_mask(idx); }
+    if (delta_mm < 0.0 ) { block->direction_bits |= get_direction_pin_mask(idx); }
    // Incrementally compute total move distance by Euclidean norm. First add square of each term.
    block->millimeters += delta_mm*delta_mm;
  }
  block->millimeters = sqrt(block->millimeters); // Complete millimeters calculation with sqrt()
  // Bail if this is a zero-length block. Highly unlikely to occur.
  if (block->step_event_count == 0) { return(PLAN_EMPTY_BLOCK); }
  // Adjust feed_rate value to mm/min depending on type of rate input (normal, inverse time, or rapids)
  // TODO: Need to distinguish a rapids vs feed move for overrides. Some flag of some sort.
  if (feed_rate < 0) { feed_rate = SOME_LARGE_VALUE; } // Scaled down to absolute max/rapids rate later
  else if (invert_feed_rate) { feed_rate *= block->millimeters; }
  if (feed_rate < MINIMUM_FEED_RATE) { feed_rate = MINIMUM_FEED_RATE; } // Prevents step generation round-off condition.
  // Calculate the unit vector of the line move and the block maximum feed rate and acceleration scaled
  // down such that no individual axes maximum values are exceeded with respect to the line direction.
  // NOTE: This calculation assumes all axes are orthogonal (Cartesian) and works with ABC-axes,
  // if they are also orthogonal/independent. Operates on the absolute value of the unit vector.
-  float inverse_unit_vec_value;
+  block->millimeters = convert_delta_vector_to_unit_vector(unit_vec);
-  float inverse_millimeters = 1.0/block->millimeters;  // Inverse millimeters to remove multiple float divides	
+  block->acceleration = limit_value_by_axis_maximum(settings.acceleration, unit_vec);
-  float junction_cos_theta = 0.0;
+  block->rapid_rate = limit_value_by_axis_maximum(settings.max_rate, unit_vec);
  for (idx=0; idx<N_AXIS; idx++) {
    if (unit_vec[idx] != 0) {  // Avoid divide by zero.
      unit_vec[idx] *= inverse_millimeters;  // Complete unit vector calculation
      inverse_unit_vec_value = fabs(1.0/unit_vec[idx]); // Inverse to remove multiple float divides.
-      // Check and limit feed rate against max individual axis velocities and accelerations
+  // Store programmed rate.
-      feed_rate = min(feed_rate,settings.max_rate[idx]*inverse_unit_vec_value);
+  block->programmed_rate = pl_data->feed_rate;
-      block->acceleration = min(block->acceleration,settings.acceleration[idx]*inverse_unit_vec_value);
+  if (block->condition & PL_COND_FLAG_INVERSE_TIME) { block->programmed_rate *= block->millimeters; }
      // Incrementally compute cosine of angle between previous and current path. Cos(theta) of the junction
      // between the current move and the previous move is simply the dot product of the two unit vectors, 
      // where prev_unit_vec is negative. Used later to compute maximum junction speed.
      junction_cos_theta -= pl.previous_unit_vec[idx] * unit_vec[idx];
    }
  }
  // TODO: Need to check this method handling zero junction speeds when starting from rest.
-  if ((block_buffer_head == block_buffer_tail) || is_parking_motion) {
+  if ((block_buffer_head == block_buffer_tail) || (block->condition & PL_COND_FLAG_SYSTEM_MOTION)) {
    // Initialize block entry speed as zero. Assume it will be starting from rest. Planner will correct this later.
-    // If parking motion, the parking block always is assumed to start from rest and end at a complete stop.
+    // If system motion, the system motion block always is assumed to start from rest and end at a complete stop.
    block->entry_speed_sqr = 0.0;
    block->max_junction_speed_sqr = 0.0; // Starting from rest. Enforce start from zero velocity.
  } else {
-    /* 
+    // Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
-       Compute maximum allowable entry speed at junction by centripetal acceleration approximation.
+    // Let a circle be tangent to both previous and current path line segments, where the junction
-       Let a circle be tangent to both previous and current path line segments, where the junction 
+    // deviation is defined as the distance from the junction to the closest edge of the circle,
-       deviation is defined as the distance from the junction to the closest edge of the circle, 
+    // colinear with the circle center. The circular segment joining the two paths represents the
-       colinear with the circle center. The circular segment joining the two paths represents the 
+    // path of centripetal acceleration. Solve for max velocity based on max acceleration about the
-       path of centripetal acceleration. Solve for max velocity based on max acceleration about the
+    // radius of the circle, defined indirectly by junction deviation. This may be also viewed as
-       radius of the circle, defined indirectly by junction deviation. This may be also viewed as 
+    // path width or max_jerk in the previous Grbl version. This approach does not actually deviate
-       path width or max_jerk in the previous Grbl version. This approach does not actually deviate 
+    // from path, but used as a robust way to compute cornering speeds, as it takes into account the
-       from path, but used as a robust way to compute cornering speeds, as it takes into account the
+    // nonlinearities of both the junction angle and junction velocity.
-       nonlinearities of both the junction angle and junction velocity.
+    //
    // NOTE: If the junction deviation value is finite, Grbl executes the motions in an exact path
    // mode (G61). If the junction deviation value is zero, Grbl will execute the motion in an exact
    // stop mode (G61.1) manner. In the future, if continuous mode (G64) is desired, the math here
    // is exactly the same. Instead of motioning all the way to junction point, the machine will
    // just follow the arc circle defined here. The Arduino doesn't have the CPU cycles to perform
    // a continuous mode path, but ARM-based microcontrollers most certainly do.
    //
    // NOTE: The max junction speed is a fixed value, since machine acceleration limits cannot be
    // changed dynamically during operation nor can the line move geometry. This must be kept in
    // memory in the event of a feedrate override changing the nominal speeds of blocks, which can
    // change the overall maximum entry speed conditions of all blocks.
-       NOTE: If the junction deviation value is finite, Grbl executes the motions in an exact path 
+    float junction_unit_vec[N_AXIS];
-       mode (G61). If the junction deviation value is zero, Grbl will execute the motion in an exact
+    float junction_cos_theta = 0.0;
-       stop mode (G61.1) manner. In the future, if continuous mode (G64) is desired, the math here
+    for (idx=0; idx<N_AXIS; idx++) {
-       is exactly the same. Instead of motioning all the way to junction point, the machine will
+      junction_cos_theta -= pl.previous_unit_vec[idx]*unit_vec[idx];
-       just follow the arc circle defined here. The Arduino doesn't have the CPU cycles to perform
+      junction_unit_vec[idx] = unit_vec[idx]-pl.previous_unit_vec[idx];
-       a continuous mode path, but ARM-based microcontrollers most certainly do. 
+    }
       NOTE: The max junction speed is a fixed value, since machine acceleration limits cannot be
       changed dynamically during operation nor can the line move geometry. This must be kept in
       memory in the event of a feedrate override changing the nominal speeds of blocks, which can 
       change the overall maximum entry speed conditions of all blocks.
    */
    // NOTE: Computed without any expensive trig, sin() or acos(), by trig half angle identity of cos(theta).
    if (junction_cos_theta > 0.999999) {
      //  For a 0 degree acute junction, just set minimum junction speed.
      block->max_junction_speed_sqr = MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED;
    } else {
-      junction_cos_theta = max(junction_cos_theta,-0.999999); // Check for numerical round-off to avoid divide by zero.
+      if (junction_cos_theta < -0.999999) {
        // Junction is a straight line or 180 degrees. Junction speed is infinite.
        block->max_junction_speed_sqr = SOME_LARGE_VALUE;
      } else {
        convert_delta_vector_to_unit_vector(junction_unit_vec);
        float junction_acceleration = limit_value_by_axis_maximum(settings.acceleration, junction_unit_vec);
        float sin_theta_d2 = sqrt(0.5*(1.0-junction_cos_theta)); // Trig half angle identity. Always positive.
      // TODO: Technically, the acceleration used in calculation needs to be limited by the minimum of the
      // two junctions. However, this shouldn't be a significant problem except in extreme circumstances.
        block->max_junction_speed_sqr = max( MINIMUM_JUNCTION_SPEED*MINIMUM_JUNCTION_SPEED,
-                     (block->acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2) );
+                       (junction_acceleration * settings.junction_deviation * sin_theta_d2)/(1.0-sin_theta_d2) );
-
+      }
    }
  }
-  // Store block nominal speed
+  // Block system motion from updating this data to ensure next g-code motion is computed correctly.
-  block->nominal_speed_sqr = feed_rate*feed_rate; // (mm/min). Always > 0
+  if (!(block->condition & PL_COND_FLAG_SYSTEM_MOTION)) {
    float nominal_speed = plan_compute_profile_nominal_speed(block);
    plan_compute_profile_parameters(block, nominal_speed, pl.previous_nominal_speed);
    pl.previous_nominal_speed = nominal_speed;
-  // Compute the junction maximum entry based on the minimum of the junction speed and neighboring nominal speeds.
+    // Update previous path unit_vector and planner position.
  block->max_entry_speed_sqr = min(block->max_junction_speed_sqr, 
 								   min(block->nominal_speed_sqr,pl.previous_nominal_speed_sqr));
  // Block parking motion from updating this data to ensure next g-code motion is computed correctly.
  if (!is_parking_motion) {
    // Update previous path unit_vector and nominal speed (squared)
    memcpy(pl.previous_unit_vec, unit_vec, sizeof(unit_vec)); // pl.previous_unit_vec[] = unit_vec[]
    pl.previous_nominal_speed_sqr = block->nominal_speed_sqr;
    // Update planner position
    memcpy(pl.position, target_steps, sizeof(target_steps)); // pl.position[] = target_steps[]
    // New block is all set. Update buffer head and next buffer head indices.
@ -444,21 +473,30 @@ void plan_sync_position()
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    #ifdef COREXY
-      if (idx==A_MOTOR) { 
+      if (idx==X_AXIS) {
-        pl.position[idx] = (sys.position[A_MOTOR] + sys.position[B_MOTOR])/2;
+        pl.position[X_AXIS] = system_convert_corexy_to_x_axis_steps(sys_position);
-      } else if (idx==B_MOTOR) { 
+      } else if (idx==Y_AXIS) {
-        pl.position[idx] = (sys.position[A_MOTOR] - sys.position[B_MOTOR])/2;
+        pl.position[Y_AXIS] = system_convert_corexy_to_y_axis_steps(sys_position);
      } else {
-        pl.position[idx] = sys.position[idx];
+        pl.position[idx] = sys_position[idx];
      }
    #else
-      pl.position[idx] = sys.position[idx];
+      pl.position[idx] = sys_position[idx];
    #endif
  }
 }
 // Returns the number of available blocks are in the planner buffer.
 uint8_t plan_get_block_buffer_available()
 {
  if (block_buffer_head >= block_buffer_tail) { return((BLOCK_BUFFER_SIZE-1)-(block_buffer_head-block_buffer_tail)); }
  return((block_buffer_tail-block_buffer_head-1));
 }
 // Returns the number of active blocks are in the planner buffer.
 // NOTE: Deprecated. Not used unless classic status reports are enabled in config.h
 uint8_t plan_get_block_buffer_count()
 {
  if (block_buffer_head >= block_buffer_tail) { return(block_buffer_head-block_buffer_tail); }
--- a/grbl/planner.h
+++ b/grbl/planner.h
@ -2,7 +2,7 @@
  planner.h - buffers movement commands and manages the acceleration profile plan
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon 
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -26,59 +26,89 @@
 // The number of linear motions that can be in the plan at any give time
 #ifndef BLOCK_BUFFER_SIZE
  #ifdef USE_LINE_NUMBERS
-    #define BLOCK_BUFFER_SIZE 16
+    #define BLOCK_BUFFER_SIZE 15
  #else
-    #define BLOCK_BUFFER_SIZE 18
+    #define BLOCK_BUFFER_SIZE 17
  #endif
 #endif
 // Returned status message from planner.
 #define PLAN_OK true
 #define PLAN_EMPTY_BLOCK false
 // Define planner data condition flags. Used to denote running conditions of a block.
 #define PL_COND_FLAG_RAPID_MOTION      bit(0)
 #define PL_COND_FLAG_SYSTEM_MOTION     bit(1) // Single motion. Circumvents planner state. Used by home/park.
 #define PL_COND_FLAG_NO_FEED_OVERRIDE  bit(2) // Motion does not honor feed override.
 #define PL_COND_FLAG_INVERSE_TIME      bit(3)
 #define PL_COND_FLAG_SPINDLE_CW        bit(4)
 #define PL_COND_FLAG_SPINDLE_CCW       bit(5)
 #define PL_COND_FLAG_COOLANT_FLOOD     bit(6)
 #define PL_COND_FLAG_COOLANT_MIST      bit(7)
 // This struct stores a linear movement of a g-code block motion with its critical "nominal" values
 // are as specified in the source g-code.
 typedef struct {
  // Fields used by the bresenham algorithm for tracing the line
  // NOTE: Used by stepper algorithm to execute the block correctly. Do not alter these values.
  uint8_t direction_bits;    // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
  uint32_t steps[N_AXIS];    // Step count along each axis
  uint32_t step_event_count; // The maximum step axis count and number of steps required to complete this block.
  uint8_t direction_bits;    // The direction bit set for this block (refers to *_DIRECTION_BIT in config.h)
  // Block condition data to ensure correct execution depending on states and overrides.
  uint8_t condition;      // Block bitflag variable defining block run conditions. Copied from pl_line_data.
  #ifdef USE_LINE_NUMBERS
    int32_t line_number;  // Block line number for real-time reporting. Copied from pl_line_data.
  #endif
  // Fields used by the motion planner to manage acceleration. Some of these values may be updated
  // by the stepper module during execution of special motion cases for replanning purposes.
  float entry_speed_sqr;     // The current planned entry speed at block junction in (mm/min)^2
  float max_entry_speed_sqr; // Maximum allowable entry speed based on the minimum of junction limit and
                             //   neighboring nominal speeds with overrides in (mm/min)^2
-  float max_junction_speed_sqr;  // Junction entry speed limit based on direction vectors in (mm/min)^2
+  float acceleration;        // Axis-limit adjusted line acceleration in (mm/min^2). Does not change.
-  float nominal_speed_sqr;       // Axis-limit adjusted nominal speed for this block in (mm/min)^2
+  float millimeters;         // The remaining distance for this block to be executed in (mm).
-  float acceleration;            // Axis-limit adjusted line acceleration in (mm/min^2)
+                             // NOTE: This value may be altered by stepper algorithm during execution.
  float millimeters;             // The remaining distance for this block to be executed in (mm)
  // uint8_t max_override;       // Maximum override value based on axis speed limits
-  #ifdef USE_LINE_NUMBERS
+  // Stored rate limiting data used by planner when changes occur.
-    int32_t line_number;
+  float max_junction_speed_sqr; // Junction entry speed limit based on direction vectors in (mm/min)^2
  float rapid_rate;             // Axis-limit adjusted maximum rate for this block direction in (mm/min)
  float programmed_rate;        // Programmed rate of this block (mm/min).
  #ifdef VARIABLE_SPINDLE
    // Stored spindle speed data used by spindle overrides and resuming methods.
    float spindle_speed;    // Block spindle speed. Copied from pl_line_data.
  #endif
 } plan_block_t;
 // Planner data prototype. Must be used when passing new motions to the planner.
 typedef struct {
  float feed_rate;          // Desired feed rate for line motion. Value is ignored, if rapid motion.
  float spindle_speed;      // Desired spindle speed through line motion.
  uint8_t condition;        // Bitflag variable to indicate planner conditions. See defines above.
  #ifdef USE_LINE_NUMBERS
    int32_t line_number;    // Desired line number to report when executing.
  #endif
 } plan_line_data_t;
 // Initialize and reset the motion plan subsystem
-void plan_reset();
+void plan_reset(); // Reset all
 void plan_reset_buffer(); // Reset buffer only.
 // Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position
 // in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
 // rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
-#ifdef USE_LINE_NUMBERS
+uint8_t plan_buffer_line(float *target, plan_line_data_t *pl_data);
  uint8_t plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_parking_motion, int32_t line_number);
 #else
  uint8_t plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint8_t is_parking_motion);
 #endif
 // Called when the current block is no longer needed. Discards the block and makes the memory
 // availible for new blocks.
 void plan_discard_current_block();
-// Gets the planner block for the parking special motion case. Parking uses the always available buffer head.
+// Gets the planner block for the special system motion cases. (Parking/Homing)
-plan_block_t *plan_get_parking_block();
+plan_block_t *plan_get_system_motion_block();
 // Gets the current block. Returns NULL if buffer empty
 plan_block_t *plan_get_current_block();
@ -87,7 +117,13 @@ plan_block_t *plan_get_current_block();
 uint8_t plan_next_block_index(uint8_t block_index);
 // Called by step segment buffer when computing executing block velocity profile.
-float plan_get_exec_block_exit_speed();
+float plan_get_exec_block_exit_speed_sqr();
 // Called by main program during planner calculations and step segment buffer during initialization.
 float plan_compute_profile_nominal_speed(plan_block_t *block);
 // Re-calculates buffered motions profile parameters upon a motion-based override change.
 void plan_update_velocity_profile_parameters();
 // Reset the planner position vector (in steps)
 void plan_sync_position();
@ -95,10 +131,17 @@ void plan_sync_position();
 // Reinitialize plan with a partially completed block
 void plan_cycle_reinitialize();
 // Returns the number of available blocks are in the planner buffer.
 uint8_t plan_get_block_buffer_available();
 // Returns the number of active blocks are in the planner buffer.
 // NOTE: Deprecated. Not used unless classic status reports are enabled in config.h
 uint8_t plan_get_block_buffer_count();
 // Returns the status of the block ring buffer. True, if buffer is full.
 uint8_t plan_check_full_buffer();
 void plan_get_planner_mpos(float *target);
 #endif
--- a/grbl/print.c
+++ b/grbl/print.c
@ -2,7 +2,7 @@
  print.c - Functions for formatting output strings
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -60,15 +60,33 @@ void printPgmString(const char *s)
 // }
-// Prints an uint8 variable with base and number of desired digits.
+// Prints an uint8 variable in base 10.
-void print_unsigned_int8(uint8_t n, uint8_t base, uint8_t digits)
+void print_uint8_base10(uint8_t n)
 {
  uint8_t digit_a = 0;
  uint8_t digit_b = 0;
  if (n >= 100) { // 100-255
    digit_a = '0' + n % 10;
    n /= 10;
  }
  if (n >= 10) { // 10-99
    digit_b = '0' + n % 10;
    n /= 10;
  }
  serial_write('0' + n);
  if (digit_b) { serial_write(digit_b); }
  if (digit_a) { serial_write(digit_a); }
 }
 // Prints an uint8 variable in base 2 with desired number of desired digits.
 void print_uint8_base2_ndigit(uint8_t n, uint8_t digits) {
  unsigned char buf[digits];
  uint8_t i = 0;
  for (; i < digits; i++) {
-      buf[i] = n % base ;
+      buf[i] = n % 2 ;
-      n /= base;
+      n /= 2;
  }
  for (; i > 0; i--)
@ -76,23 +94,6 @@ void print_unsigned_int8(uint8_t n, uint8_t base, uint8_t digits)
 }
 // Prints an uint8 variable in base 2.
 void print_uint8_base2(uint8_t n) {
  print_unsigned_int8(n,2,8);
 }
 // Prints an uint8 variable in base 10.
 void print_uint8_base10(uint8_t n)
 {   
  uint8_t digits;
  if (n < 10) { digits = 1; } 
  else if (n < 100) { digits = 2; }
  else { digits = 3; }
  print_unsigned_int8(n,10,digits);
 }
 void print_uint32_base10(uint32_t n)
 {
  if (n == 0) {
@ -145,7 +146,7 @@ void printFloat(float n, uint8_t decimal_places)
  n += 0.5; // Add rounding factor. Ensures carryover through entire value.
  // Generate digits backwards and store in string.
-  unsigned char buf[10]; 
+  unsigned char buf[13];
  uint8_t i = 0;
  uint32_t a = (long)n;
  buf[decimal_places] = '.'; // Place decimal point, even if decimal places are zero.
@ -172,7 +173,6 @@ void printFloat(float n, uint8_t decimal_places)
 // in the config.h.
 //  - CoordValue: Handles all position or coordinate values in inches or mm reporting.
 //  - RateValue: Handles feed rate and current velocity in inches or mm reporting.
 //  - SettingValue: Handles all floating point settings values (always in mm.)
 void printFloat_CoordValue(float n) {
  if (bit_istrue(settings.flags,BITFLAG_REPORT_INCHES)) {
    printFloat(n*INCH_PER_MM,N_DECIMAL_COORDVALUE_INCH);
@ -189,10 +189,6 @@ void printFloat_RateValue(float n) {
  }
 }
 void printFloat_SettingValue(float n) { printFloat(n,N_DECIMAL_SETTINGVALUE); }
 void printFloat_RPMValue(float n) { printFloat(n,N_DECIMAL_RPMVALUE); }
 // Debug tool to print free memory in bytes at the called point.
 // NOTE: Keep commented unless using. Part of this function always gets compiled in.
 // void printFreeMemory()
--- a/grbl/print.h
+++ b/grbl/print.h
@ -2,7 +2,7 @@
  print.h - Functions for formatting output strings
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -31,26 +31,19 @@ void printInteger(long n);
 void print_uint32_base10(uint32_t n);
 // Prints uint8 variable with base and number of desired digits.
 void print_unsigned_int8(uint8_t n, uint8_t base, uint8_t digits); 
 // Prints an uint8 variable in base 2.
 void print_uint8_base2(uint8_t n);
 // Prints an uint8 variable in base 10.
 void print_uint8_base10(uint8_t n);
 // Prints an uint8 variable in base 2 with desired number of desired digits.
 void print_uint8_base2_ndigit(uint8_t n, uint8_t digits);
 void printFloat(float n, uint8_t decimal_places);
 // Floating value printing handlers for special variables types used in Grbl.
 //  - CoordValue: Handles all position or coordinate values in inches or mm reporting.
 //  - RateValue: Handles feed rate and current velocity in inches or mm reporting.
 //  - SettingValue: Handles all floating point settings values (always in mm.)
 //  - RPMValue: Handles spindle RPM values in settings and reports.
 void printFloat_CoordValue(float n);
 void printFloat_RateValue(float n);
 void printFloat_SettingValue(float n);
 void printFloat_RPMValue(float n);
 // Debug tool to print free memory in bytes at the called point. Not used otherwise.
 void printFreeMemory();
--- a/grbl/probe.c
+++ b/grbl/probe.c
@ -2,7 +2,7 @@
  probe.c - code pertaining to probing methods
  Part of Grbl
-  Copyright (c) 2014-2015 Sungeun K. Jeon
+  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -34,7 +34,7 @@ void probe_init()
  #else
    PROBE_PORT |= PROBE_MASK;    // Enable internal pull-up resistors. Normal high operation.
  #endif
-  probe_configure_invert_mask(false); // Initialize invert mask. Re-updated during use.
+  probe_configure_invert_mask(false); // Initialize invert mask.
 }
@ -58,11 +58,9 @@ uint8_t probe_get_state() { return((PROBE_PIN & PROBE_MASK) ^ probe_invert_mask)
 // NOTE: This function must be extremely efficient as to not bog down the stepper ISR.
 void probe_state_monitor()
 {
  if (sys_probe_state == PROBE_ACTIVE) {
  if (probe_get_state()) {
    sys_probe_state = PROBE_OFF;
-      memcpy(sys.probe_position, sys.position, sizeof(sys.position));
+    memcpy(sys_probe_position, sys_position, sizeof(sys_position));
    bit_true(sys_rt_exec_state, EXEC_MOTION_CANCEL);
  }
  }
 }
--- a/grbl/probe.h
+++ b/grbl/probe.h
@ -2,7 +2,7 @@
  probe.h - code pertaining to probing methods
  Part of Grbl
-  Copyright (c) 2014-2015 Sungeun K. Jeon
+  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
--- a/grbl/protocol.c
+++ b/grbl/protocol.c
@ -2,7 +2,7 @@
  protocol.c - controls Grbl execution protocol and procedures
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon  
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -37,28 +37,35 @@ static void protocol_exec_rt_suspend();
 */
 void protocol_main_loop()
 {
-  // ------------------------------------------------------------
+  // Perform some machine checks to make sure everything is good to go.
-  // Complete initialization procedures upon a power-up or reset.
+  #ifdef CHECK_LIMITS_AT_INIT
-  // ------------------------------------------------------------
+    if (bit_istrue(settings.flags, BITFLAG_HARD_LIMIT_ENABLE)) {
-  
+      if (limits_get_state()) {
-  // Print welcome message   
+        sys.state = STATE_ALARM; // Ensure alarm state is active.
-  report_init_message();
+        report_feedback_message(MESSAGE_CHECK_LIMITS);
-
+      }
    }
  #endif
  // Check for and report alarm state after a reset, error, or an initial power up.
-  if (sys.state == STATE_ALARM) {
+  // NOTE: Sleep mode disables the stepper drivers and position can't be guaranteed.
  // Re-initialize the sleep state as an ALARM mode to ensure user homes or acknowledges.
  if (sys.state & (STATE_ALARM | STATE_SLEEP)) {
    report_feedback_message(MESSAGE_ALARM_LOCK);
    sys.state = STATE_ALARM; // Ensure alarm state is set.
  } else {
-    // All systems go! But first check for safety door.
+    // Check if the safety door is open.
    sys.state = STATE_IDLE;
    if (system_check_safety_door_ajar()) {
      bit_true(sys_rt_exec_state, EXEC_SAFETY_DOOR);
      protocol_execute_realtime(); // Enter safety door mode. Should return as IDLE state.
    }
    // All systems go!
    system_execute_startup(line); // Execute startup script.
  }
  // ---------------------------------------------------------------------------------
  // Primary loop! Upon a system abort, this exits back to main() to reset the system.
  // This is also where Grbl idles while waiting for something to do.
  // ---------------------------------------------------------------------------------
  uint8_t line_flags = 0;
@ -68,14 +75,6 @@ void protocol_main_loop()
    // Process one line of incoming serial data, as the data becomes available. Performs an
    // initial filtering by removing spaces and comments and capitalizing all letters.
    // NOTE: While comment, spaces, and block delete(if supported) handling should technically 
    // be done in the g-code parser, doing it here helps compress the incoming data into Grbl's
    // line buffer, which is limited in size. The g-code standard actually states a line can't
    // exceed 256 characters, but the Arduino Uno does not have the memory space for this.
    // With a better processor, it would be very easy to pull this initial parsing out as a 
    // seperate task to be shared by the g-code parser and Grbl's system commands.
    while((c = serial_read()) != SERIAL_NO_DATA) {
      if ((c == '\n') || (c == '\r')) { // End of line reached
@ -97,9 +96,9 @@ void protocol_main_loop()
        } else if (line[0] == '$') {
          // Grbl '$' system command
          report_status_message(system_execute_line(line));
-        } else if (sys.state == STATE_ALARM) {
+        } else if (sys.state & (STATE_ALARM | STATE_JOG)) {
-          // Everything else is gcode. Block if in alarm mode.
+          // Everything else is gcode. Block if in alarm or jog mode.
-          report_status_message(STATUS_ALARM_LOCK); 
+          report_status_message(STATUS_SYSTEM_GC_LOCK);
        } else {
          // Parse and execute g-code block.
          report_status_message(gc_execute_line(line));
@ -159,7 +158,6 @@ void protocol_main_loop()
    protocol_execute_realtime();  // Runtime command check point.
    if (sys.abort) { return; } // Bail to main() program loop to reset system.
  }
  return; /* Never reached */
@ -179,18 +177,18 @@ void protocol_buffer_synchronize()
 }
-// Auto-cycle start has two purposes: 1. Resumes a plan_synchronize() call from a function that
+// Auto-cycle start triggers when there is a motion ready to execute and if the main program is not
-// requires the planner buffer to empty (spindle enable, dwell, etc.) 2. As a user setting that 
+// actively parsing commands.
 // automatically begins the cycle when a user enters a valid motion command manually. This is 
 // intended as a beginners feature to help new users to understand g-code. It can be disabled
 // as a beginner tool, but (1.) still operates. If disabled, the operation of cycle start is
 // manually issuing a cycle start command whenever the user is ready and there is a valid motion 
 // command in the planner queue.
 // NOTE: This function is called from the main loop, buffer sync, and mc_line() only and executes
 // when one of these conditions exist respectively: There are no more blocks sent (i.e. streaming
 // is finished, single commands), a command that needs to wait for the motions in the buffer to
 // execute calls a buffer sync, or the planner buffer is full and ready to go.
-void protocol_auto_cycle_start() { system_set_exec_state_flag(EXEC_CYCLE_START); } 
+void protocol_auto_cycle_start()
 {
  if (plan_get_current_block() != NULL) { // Check if there are any blocks in the buffer.
    system_set_exec_state_flag(EXEC_CYCLE_START); // If so, execute them!
  }
 }
 // This function is the general interface to Grbl's real-time command execution system. It is called
@ -223,19 +221,9 @@ void protocol_exec_rt_system()
    // the source of the error to the user. If critical, Grbl disables by entering an infinite
    // loop until system reset/abort.
    sys.state = STATE_ALARM; // Set system alarm state
-    if (rt_exec & EXEC_ALARM_HARD_LIMIT) {
+    report_alarm_message(rt_exec);
      report_alarm_message(ALARM_HARD_LIMIT_ERROR); 
    } else if (rt_exec & EXEC_ALARM_SOFT_LIMIT) {
      report_alarm_message(ALARM_SOFT_LIMIT_ERROR);
    } else if (rt_exec & EXEC_ALARM_ABORT_CYCLE) {      
      report_alarm_message(ALARM_ABORT_CYCLE);
    } else if (rt_exec & EXEC_ALARM_PROBE_FAIL) {
      report_alarm_message(ALARM_PROBE_FAIL);
    } else if (rt_exec & EXEC_ALARM_HOMING_FAIL) {
      report_alarm_message(ALARM_HOMING_FAIL);
    }
    // Halt everything upon a critical event flag. Currently hard and soft limits flag this.
-    if (rt_exec & EXEC_CRITICAL_EVENT) {
+    if ((rt_exec == EXEC_ALARM_HARD_LIMIT) || (rt_exec == EXEC_ALARM_SOFT_LIMIT)) {
      report_feedback_message(MESSAGE_CRITICAL_EVENT);
      system_clear_exec_state_flag(EXEC_RESET); // Disable any existing reset
      do {
@ -243,14 +231,7 @@ void protocol_exec_rt_system()
        // cycles. Hard limits typically occur while unattended or not paying attention. Gives
        // the user and a GUI time to do what is needed before resetting, like killing the
        // incoming stream. The same could be said about soft limits. While the position is not
-        // lost, streaming could cause a serious crash if it continues afterwards.
+        // lost, continued streaming could cause a serious crash if by chance it gets executed.
 // TODO: Allow status reports during a critical alarm. Still need to think about implications of this.
        // if (sys_rt_exec_state & EXEC_STATUS_REPORT) { 
        //   report_realtime_status();
        //   system_clear_exec_state_flag(EXEC_STATUS_REPORT); 
        // }
      } while (bit_isfalse(sys_rt_exec_state,EXEC_RESET));
    }
    system_clear_exec_alarm_flag(0xFF); // Clear all alarm flags
@ -271,42 +252,39 @@ void protocol_exec_rt_system()
      system_clear_exec_state_flag(EXEC_STATUS_REPORT);
    }
-    // NOTE: The math involved to calculate the hold should be low enough for most, if not all, 
+    // NOTE: Once hold is initiated, the system immediately enters a suspend state to block all
-    // operational scenarios. Once hold is initiated, the system enters a suspend state to block
+    // main program processes until either reset or resumed. This ensures a hold completes safely.
-    // all main program processes until either reset or resumed.
+    if (rt_exec & (EXEC_MOTION_CANCEL | EXEC_FEED_HOLD | EXEC_SAFETY_DOOR | EXEC_SLEEP)) {
    if (rt_exec & (EXEC_MOTION_CANCEL | EXEC_FEED_HOLD | EXEC_SAFETY_DOOR)) {
      // TODO: CHECK MODE? How to handle this? Likely nothing, since it only works when IDLE and then resets Grbl.
      // State check for allowable states for hold methods.
-      if ((sys.state == STATE_IDLE) || (sys.state & (STATE_CYCLE | STATE_HOMING | STATE_MOTION_CANCEL | STATE_HOLD | STATE_SAFETY_DOOR))) {
+      if (!(sys.state & (STATE_ALARM | STATE_CHECK_MODE))) {
-        // If in CYCLE state, all hold states immediately initiate a motion HOLD.
+        // If in CYCLE or JOG states, immediately initiate a motion HOLD.
-        if (sys.state == STATE_CYCLE) {
+        if (sys.state & (STATE_CYCLE | STATE_JOG)) {
          if (!(sys.suspend & (SUSPEND_MOTION_CANCEL | SUSPEND_JOG_CANCEL))) { // Block, if already holding.
            st_update_plan_block_parameters(); // Notify stepper module to recompute for hold deceleration.
            sys.step_control = STEP_CONTROL_EXECUTE_HOLD; // Initiate suspend state with active flag.
            if (sys.state == STATE_JOG) { // Jog cancelled upon any hold event, except for sleeping.
              if (!(rt_exec & EXEC_SLEEP)) { sys.suspend |= SUSPEND_JOG_CANCEL; } 
            }
          }
        }
        // If IDLE, Grbl is not in motion. Simply indicate suspend state and hold is complete.
-        if (sys.state == STATE_IDLE) { 
+        if (sys.state == STATE_IDLE) { sys.suspend = SUSPEND_HOLD_COMPLETE; }
          sys.suspend = SUSPEND_HOLD_COMPLETE;
          sys.step_control = STEP_CONTROL_END_MOTION; 
        }
        // Execute and flag a motion cancel with deceleration and return to idle. Used primarily by probing cycle
        // to halt and cancel the remainder of the motion.
        if (rt_exec & EXEC_MOTION_CANCEL) {
          // MOTION_CANCEL only occurs during a CYCLE, but a HOLD and SAFETY_DOOR may been initiated beforehand
-          // to hold the CYCLE. If so, only flag that motion cancel is complete.
+          // to hold the CYCLE. Motion cancel is valid for a single planner block motion only, while jog cancel
-          if (sys.state == STATE_CYCLE) { sys.state = STATE_MOTION_CANCEL; }
+          // will handle and clear multiple planner block motions.
-          // NOTE: Ensures the motion cancel is handled correctly if it is active during a HOLD or DOOR state.
+          if (!(sys.state & STATE_JOG)) { sys.suspend |= SUSPEND_MOTION_CANCEL; } // NOTE: State is STATE_CYCLE.
          sys.suspend |= SUSPEND_MOTION_CANCEL;  // Indicate motion cancel when resuming.
        }
        // Execute a feed hold with deceleration, if required. Then, suspend system.
        if (rt_exec & EXEC_FEED_HOLD) {
-          // Block SAFETY_DOOR state from prematurely changing back to HOLD, which should only
+          // Block SAFETY_DOOR, JOG, and SLEEP states from changing to HOLD state.
-          // occur if the safety door switch closes.
+          if (!(sys.state & (STATE_SAFETY_DOOR | STATE_JOG | STATE_SLEEP))) { sys.state = STATE_HOLD; }
          if (sys.state != STATE_SAFETY_DOOR) { sys.state = STATE_HOLD; }
        }
        // Execute a safety door stop with a feed hold and disable spindle/coolant.
@ -314,16 +292,17 @@ void protocol_exec_rt_system()
        // devices (spindle/coolant), and blocks resuming until switch is re-engaged.
        if (rt_exec & EXEC_SAFETY_DOOR) {
          report_feedback_message(MESSAGE_SAFETY_DOOR_AJAR);
-        
+          // If jogging, block safety door methods until jog cancel is complete. Just flag that it happened.
          if (!(sys.suspend & SUSPEND_JOG_CANCEL)) {
            // Check if the safety re-opened during a restore parking motion only. Ignore if
-          // already retracting or parked.
+            // already retracting, parked or in sleep state.
-          if (sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) {
+            if (sys.state == STATE_SAFETY_DOOR) {
              if (sys.suspend & SUSPEND_INITIATE_RESTORE) { // Actively restoring
                #ifdef PARKING_ENABLE
                  // Set hold and reset appropriate control flags to restart parking sequence.
-                if (sys.step_control & STEP_CONTROL_EXECUTE_PARK) {
+                  if (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION) {
                    st_update_plan_block_parameters(); // Notify stepper module to recompute for hold deceleration.
-                  sys.step_control = (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_PARK);
+                    sys.step_control = (STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_SYS_MOTION);
                    sys.suspend &= ~(SUSPEND_HOLD_COMPLETE);
                  } // else NO_MOTION is active.
                #endif
@ -331,16 +310,21 @@ void protocol_exec_rt_system()
                sys.suspend |= SUSPEND_RESTART_RETRACT;
              }
            }
-        
+            if (sys.state != STATE_SLEEP) { sys.state = STATE_SAFETY_DOOR; }
          }
          // NOTE: This flag doesn't change when the door closes, unlike sys.state. Ensures any parking motions
          // are executed if the door switch closes and the state returns to HOLD.
          sys.suspend |= SUSPEND_SAFETY_DOOR_AJAR;
          sys.state = STATE_SAFETY_DOOR;
        }
      }
-      system_clear_exec_state_flag((EXEC_MOTION_CANCEL | EXEC_FEED_HOLD | EXEC_SAFETY_DOOR));      
+      if (rt_exec & EXEC_SLEEP) {
        if (sys.state == STATE_ALARM) { sys.suspend |= (SUSPEND_RETRACT_COMPLETE|SUSPEND_HOLD_COMPLETE); }
        sys.state = STATE_SLEEP; 
      }
      system_clear_exec_state_flag((EXEC_MOTION_CANCEL | EXEC_FEED_HOLD | EXEC_SAFETY_DOOR | EXEC_SLEEP));
    }
    // Execute a cycle start by starting the stepper interrupt to begin executing the blocks in queue.
@ -348,24 +332,24 @@ void protocol_exec_rt_system()
      // Block if called at same time as the hold commands: feed hold, motion cancel, and safety door.
      // Ensures auto-cycle-start doesn't resume a hold without an explicit user-input.
      if (!(rt_exec & (EXEC_FEED_HOLD | EXEC_MOTION_CANCEL | EXEC_SAFETY_DOOR))) {
-        // Cycle start only when IDLE or when a hold is complete and ready to resume.
+        // Resume door state when parking motion has retracted and door has been closed.
-        // NOTE: SAFETY_DOOR is implicitly blocked. It reverts to HOLD when the door is closed.
+        if ((sys.state == STATE_SAFETY_DOOR) && !(sys.suspend & SUSPEND_SAFETY_DOOR_AJAR)) {
-        if ((sys.state == STATE_IDLE) || ((sys.state & (STATE_HOLD | STATE_MOTION_CANCEL)) && (sys.suspend & SUSPEND_HOLD_COMPLETE))) { 
+          if (sys.suspend & SUSPEND_RESTORE_COMPLETE) {
-          if (sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) {
+            sys.state = STATE_IDLE; // Set to IDLE to immediately resume the cycle.
-            if (sys.suspend & SUSPEND_RETRACT_COMPLETE) {
+          } else if (sys.suspend & SUSPEND_RETRACT_COMPLETE) {
              if bit_isfalse(sys.suspend,SUSPEND_RESTORE_COMPLETE) {
            // Flag to re-energize powered components and restore original position, if disabled by SAFETY_DOOR.
            // NOTE: For a safety door to resume, the switch must be closed, as indicated by HOLD state, and
            // the retraction execution is complete, which implies the initial feed hold is not active. To
            // restore normal operation, the restore procedures must be initiated by the following flag. Once,
            // they are complete, it will call CYCLE_START automatically to resume and exit the suspend.
            sys.suspend |= SUSPEND_INITIATE_RESTORE;
          }
        }
        // Cycle start only when IDLE or when a hold is complete and ready to resume.
        if ((sys.state == STATE_IDLE) || ((sys.state & STATE_HOLD) && (sys.suspend & SUSPEND_HOLD_COMPLETE))) {
          if (sys.state == STATE_HOLD && (sys.toggle_ovr_mask & TOGGLE_OVR_STOP_ACTIVE_MASK)) {
            sys.toggle_ovr_mask |= TOGGLE_OVR_STOP_RESTORE_CYCLE; // Set to restore in suspend routine and cycle start after.
          } else {
                bit_false(sys.suspend,SUSPEND_SAFETY_DOOR_AJAR);
              }
            }
          } 
          if (!(sys.suspend & SUSPEND_SAFETY_DOOR_AJAR)) {          
            // Start cycle only if queued motions exist in planner buffer and the motion is not canceled.
            sys.step_control = STEP_CONTROL_NORMAL_OP; // Restore step control to normal operation
            if (plan_get_current_block() && bit_isfalse(sys.suspend,SUSPEND_MOTION_CANCEL)) {
@ -389,25 +373,134 @@ void protocol_exec_rt_system()
      // NOTE: Bresenham algorithm variables are still maintained through both the planner and stepper
      // cycle reinitializations. The stepper path should continue exactly as if nothing has happened.
      // NOTE: EXEC_CYCLE_STOP is set by the stepper subsystem when a cycle or feed hold completes.
-      if ((sys.state & (STATE_HOLD | STATE_SAFETY_DOOR)) && !(sys.soft_limit)) {
+      if ((sys.state & (STATE_HOLD|STATE_SAFETY_DOOR|STATE_SLEEP)) && !(sys.soft_limit) && !(sys.suspend & SUSPEND_JOG_CANCEL)) {
        // Hold complete. Set to indicate ready to resume.  Remain in HOLD or DOOR states until user
        // has issued a resume command or reset.
        plan_cycle_reinitialize();
        if (sys.step_control & STEP_CONTROL_EXECUTE_HOLD) { sys.suspend |= SUSPEND_HOLD_COMPLETE; }
-        bit_false(sys.step_control,(STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_PARK));
+        bit_false(sys.step_control,(STEP_CONTROL_EXECUTE_HOLD | STEP_CONTROL_EXECUTE_SYS_MOTION));
-      } else { // Motion is complete. Includes CYCLE, HOMING, and MOTION_CANCEL states.
+      } else {
        // Motion complete. Includes CYCLE/JOG/HOMING states and jog cancel/motion cancel/soft limit events.
        // NOTE: Motion and jog cancel both immediately return to idle after the hold completes.
        if (sys.suspend & SUSPEND_JOG_CANCEL) {   // For jog cancel, flush buffers and sync positions.
          sys.step_control = STEP_CONTROL_NORMAL_OP;
          plan_reset();
          st_reset();
          gc_sync_position();
          plan_sync_position();
        }
        if (sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) { // Only occurs when safety door opens during jog.
          sys.suspend &= ~(SUSPEND_JOG_CANCEL);
          sys.suspend |= SUSPEND_HOLD_COMPLETE;
          sys.state = STATE_SAFETY_DOOR;
        } else {
          sys.suspend = SUSPEND_DISABLE;
          sys.state = STATE_IDLE;
        }
      }
      system_clear_exec_state_flag(EXEC_CYCLE_STOP);
    }
  }
-  // Overrides flag byte (sys.override) and execution should be installed here, since they 
+  // Execute overrides.
-  // are realtime and require a direct and controlled interface to the main stepper program.
+  rt_exec = sys_rt_exec_motion_override; // Copy volatile sys_rt_exec_motion_override
  if (rt_exec) {
    system_clear_exec_motion_overrides(); // Clear all motion override flags.
    uint8_t new_f_override =  sys.f_override;
    if (rt_exec & EXEC_FEED_OVR_RESET) { new_f_override = DEFAULT_FEED_OVERRIDE; }
    if (rt_exec & EXEC_FEED_OVR_COARSE_PLUS) { new_f_override += FEED_OVERRIDE_COARSE_INCREMENT; }
    if (rt_exec & EXEC_FEED_OVR_COARSE_MINUS) { new_f_override -= FEED_OVERRIDE_COARSE_INCREMENT; }
    if (rt_exec & EXEC_FEED_OVR_FINE_PLUS) { new_f_override += FEED_OVERRIDE_FINE_INCREMENT; }
    if (rt_exec & EXEC_FEED_OVR_FINE_MINUS) { new_f_override -= FEED_OVERRIDE_FINE_INCREMENT; }
    new_f_override = min(new_f_override,MAX_FEED_RATE_OVERRIDE);
    new_f_override = max(new_f_override,MIN_FEED_RATE_OVERRIDE);
    uint8_t new_r_override = sys.r_override;
    if (rt_exec & EXEC_RAPID_OVR_RESET) { new_r_override = DEFAULT_RAPID_OVERRIDE; }
    if (rt_exec & EXEC_RAPID_OVR_MEDIUM) { new_r_override = RAPID_OVERRIDE_MEDIUM; }
    if (rt_exec & EXEC_RAPID_OVR_LOW) { new_r_override = RAPID_OVERRIDE_LOW; }
    if ((new_f_override != sys.f_override) || (new_r_override != sys.r_override)) {
      sys.f_override = new_f_override;
      sys.r_override = new_r_override;
      sys.report_ovr_counter = REPORT_OVR_REFRESH_BUSY_COUNT; // Set to report change immediately
      plan_update_velocity_profile_parameters();
      plan_cycle_reinitialize();
    }
  }
  rt_exec = sys_rt_exec_accessory_override;
  if (rt_exec) {
    system_clear_exec_accessory_overrides(); // Clear all accessory override flags.
    // NOTE: Unlike motion overrides, spindle overrides do not require a planner reinitialization.
    uint8_t last_s_override =  sys.spindle_speed_ovr;
    if (rt_exec & EXEC_SPINDLE_OVR_RESET) { last_s_override = DEFAULT_SPINDLE_SPEED_OVERRIDE; }
    if (rt_exec & EXEC_SPINDLE_OVR_COARSE_PLUS) { last_s_override += SPINDLE_OVERRIDE_COARSE_INCREMENT; }
    if (rt_exec & EXEC_SPINDLE_OVR_COARSE_MINUS) { last_s_override -= SPINDLE_OVERRIDE_COARSE_INCREMENT; }
    if (rt_exec & EXEC_SPINDLE_OVR_FINE_PLUS) { last_s_override += SPINDLE_OVERRIDE_FINE_INCREMENT; }
    if (rt_exec & EXEC_SPINDLE_OVR_FINE_MINUS) { last_s_override -= SPINDLE_OVERRIDE_FINE_INCREMENT; }
    last_s_override = min(last_s_override,MAX_SPINDLE_SPEED_OVERRIDE);
    last_s_override = max(last_s_override,MIN_SPINDLE_SPEED_OVERRIDE);
    if (last_s_override != sys.spindle_speed_ovr) {
      bit_true(sys.step_control, STEP_CONTROL_UPDATE_SPINDLE_PWM);
      sys.spindle_speed_ovr = last_s_override;
      sys.report_ovr_counter = REPORT_OVR_REFRESH_BUSY_COUNT; // Set to report change immediately
    }
    uint8_t last_toggle_ovr_mask = sys.toggle_ovr_mask;
    if (rt_exec & EXEC_SPINDLE_OVR_STOP) {
      // Toggle allowed only while in HOLD state.
      if (sys.state == STATE_HOLD) {
        if (!(last_toggle_ovr_mask & TOGGLE_OVR_STOP_ACTIVE_MASK)) { last_toggle_ovr_mask |= TOGGLE_OVR_STOP_INITIATE; }
        else if (last_toggle_ovr_mask & TOGGLE_OVR_STOP_ENABLED) { last_toggle_ovr_mask |= TOGGLE_OVR_STOP_RESTORE; }
      }
    }
    // NOTE: Since coolant state always performs a planner sync whenever it changes, g-code parser
    // state can be implicitly determine current run state at the beginning of the planner.
    if (rt_exec & (EXEC_COOLANT_FLOOD_OVR_TOGGLE | EXEC_COOLANT_MIST_OVR_TOGGLE)) {
      if ((sys.state == STATE_IDLE) || (sys.state & (STATE_CYCLE | STATE_HOLD))) {
        uint8_t coolant_state = gc_state.modal.coolant;
        #ifdef ENABLE_M7
          if (rt_exec & EXEC_COOLANT_MIST_OVR_TOGGLE) {
            if (coolant_state & COOLANT_MIST_ENABLE) { bit_false(coolant_state,COOLANT_MIST_ENABLE); }
            else { coolant_state |= COOLANT_MIST_ENABLE; }
            last_toggle_ovr_mask |= TOGGLE_OVR_MIST_COOLANT;
          }
          if (rt_exec & EXEC_COOLANT_FLOOD_OVR_TOGGLE) {
            if (coolant_state & COOLANT_FLOOD_ENABLE) { bit_false(coolant_state,COOLANT_FLOOD_ENABLE); }
            else { coolant_state |= COOLANT_FLOOD_ENABLE; }
            last_toggle_ovr_mask |= TOGGLE_OVR_FLOOD_COOLANT;
          }
        #else
          if (coolant_state & COOLANT_FLOOD_ENABLE) { bit_false(coolant_state,COOLANT_FLOOD_ENABLE); }
          else { coolant_state |= COOLANT_FLOOD_ENABLE; }
          last_toggle_ovr_mask |= TOGGLE_OVR_FLOOD_COOLANT;
        #endif
        coolant_set_state(coolant_state);
        gc_state.modal.coolant = coolant_state;
      }
    }
    if (last_toggle_ovr_mask != sys.toggle_ovr_mask) {
      sys.toggle_ovr_mask = last_toggle_ovr_mask;
      sys.report_ovr_counter = REPORT_OVR_REFRESH_BUSY_COUNT; // Set to report change immediately
    }
  }
  #ifdef DEBUG
    if (sys_rt_exec_debug) {
      report_realtime_debug();
      sys_rt_exec_debug = 0;
    }
  #endif
  // Reload step segment buffer
-  if (sys.state & (STATE_CYCLE | STATE_HOLD | STATE_MOTION_CANCEL | STATE_SAFETY_DOOR | STATE_HOMING)) { 
+  if (sys.state & (STATE_CYCLE | STATE_HOLD | STATE_SAFETY_DOOR | STATE_HOMING | STATE_SLEEP| STATE_JOG)) {
    st_prep_buffer();
  }
@ -426,60 +519,95 @@ static void protocol_exec_rt_suspend()
    float restore_target[N_AXIS];
    float parking_target[N_AXIS];
    float retract_waypoint = PARKING_PULLOUT_INCREMENT;
    plan_line_data_t plan_data;
    plan_line_data_t *pl_data = &plan_data;
    memset(pl_data,0,sizeof(plan_line_data_t));
    pl_data->condition = (PL_COND_FLAG_SYSTEM_MOTION|PL_COND_FLAG_NO_FEED_OVERRIDE);
    #ifdef USE_LINE_NUMBERS
      pl_data->line_number = PARKING_MOTION_LINE_NUMBER;
    #endif
  #endif
  plan_block_t *block = plan_get_current_block();
  uint8_t restore_condition;
  #ifdef VARIABLE_SPINDLE
    float restore_spindle_speed;
    if (block == NULL) {
      restore_condition = (gc_state.modal.spindle | gc_state.modal.coolant);
      restore_spindle_speed = gc_state.spindle_speed;
    } else {
      restore_condition = block->condition;
      restore_spindle_speed = block->spindle_speed;
    }
  #else
    float restore_spindle_speed = 0.0; // Without variable spindle, this value is unused.
    if (block == NULL) { restore_condition = (gc_state.modal.spindle | gc_state.modal.coolant); }
    else { restore_condition = block->condition; }
  #endif
  while (sys.suspend) {
    if (sys.abort) { return; }
-    // Safety door manager. Handles de/re-energizing, switch state checks, and parking motions.
+    // Block until initial hold is complete and the machine has stopped motion.
-    if ((sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) && (sys.suspend & SUSPEND_HOLD_COMPLETE)) { 
+    if (sys.suspend & SUSPEND_HOLD_COMPLETE) {
      // Parking manager. Handles de/re-energizing, switch state checks, and parking motions for 
      // the safety door and sleep states.
      if (sys.state & (STATE_SAFETY_DOOR | STATE_SLEEP)) {
        // Handles retraction motions and de-energizing.
        if (bit_isfalse(sys.suspend,SUSPEND_RETRACT_COMPLETE)) {
          // Ensure any prior spindle stop override is disabled at start of safety door routine.
          bit_false(sys.toggle_ovr_mask,TOGGLE_OVR_STOP_ACTIVE_MASK);
          #ifndef PARKING_ENABLE
            spindle_stop(); // De-energize
-          coolant_stop(); // De-energize
+            coolant_set_state(COOLANT_DISABLE); // De-energize
          #else
            // Get current position and store restore location and spindle retract waypoint.
-          system_convert_array_steps_to_mpos(parking_target,sys.position);
+            system_convert_array_steps_to_mpos(parking_target,sys_position);
            if (bit_isfalse(sys.suspend,SUSPEND_RESTART_RETRACT)) {
              memcpy(restore_target,parking_target,sizeof(parking_target));
              retract_waypoint += restore_target[PARKING_AXIS];
              retract_waypoint = min(retract_waypoint,PARKING_TARGET);
            }
-          // Execute slow pull-out parking retract motion. Parking requires homing enabled and
+            // Execute slow pull-out parking retract motion. Parking requires homing enabled, the
-          // the current location not exceeding the parking target location.
+            // current location not exceeding the parking target location, and laser mode disabled.
            // NOTE: State is will remain DOOR, until the de-energizing and retract is complete.
            if ((bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE)) &&
-                          (parking_target[PARKING_AXIS] < PARKING_TARGET)) {
+                            (parking_target[PARKING_AXIS] < PARKING_TARGET) &&
                            bit_isfalse(settings.flags,BITFLAG_LASER_MODE)) {
              // Retract spindle by pullout distance. Ensure retraction motion moves away from
              // the workpiece and waypoint motion doesn't exceed the parking target location.
              if (parking_target[PARKING_AXIS] < retract_waypoint) {
                parking_target[PARKING_AXIS] = retract_waypoint;
-              mc_parking_motion(parking_target, PARKING_PULLOUT_RATE);
+                pl_data->feed_rate = PARKING_PULLOUT_RATE;
                mc_parking_motion(parking_target, pl_data);
              }
              spindle_stop(); // De-energize
-            coolant_stop(); // De-energize
+              coolant_set_state(COOLANT_DISABLE); // De-energize
              // Execute fast parking retract motion to parking target location.
              if (parking_target[PARKING_AXIS] < PARKING_TARGET) {
                parking_target[PARKING_AXIS] = PARKING_TARGET;
-              mc_parking_motion(parking_target, PARKING_RATE);
+                pl_data->feed_rate = PARKING_RATE;
                mc_parking_motion(parking_target, pl_data);
              }
            } else {
              // Parking motion not possible. Just disable the spindle and coolant.
              // NOTE: Laser mode does not start a parking motion to ensure the laser stops immediately.
              spindle_stop(); // De-energize
-            coolant_stop(); // De-energize
+              coolant_set_state(COOLANT_DISABLE); // De-energize
            }
@ -490,11 +618,21 @@ static void protocol_exec_rt_suspend()
        } else {
          if (sys.state == STATE_SLEEP) {
            report_feedback_message(MESSAGE_SLEEP_MODE);
            // Spindle and coolant should already be stopped, but do it again just to be sure.
            spindle_stop(); // De-energize
            coolant_set_state(COOLANT_DISABLE); // De-energize
            st_go_idle(); // Disable steppers
            while (!(sys.abort)) { protocol_exec_rt_system(); } // Do nothing until reset.
            return; // Abort received. Return to re-initialize.
          }    
          // Allows resuming from parking/safety door. Actively checks if safety door is closed and ready to resume.
        // NOTE: This unlocks the SAFETY_DOOR state to a HOLD state, such that CYCLE_START can activate a resume.
          if (sys.state == STATE_SAFETY_DOOR) {
            if (!(system_check_safety_door_ajar())) {
-            sys.state = STATE_HOLD; // Update to HOLD state to indicate door is closed and ready to resume.
+              sys.suspend &= ~(SUSPEND_SAFETY_DOOR_AJAR); // Reset door ajar flag to denote ready to resume.
            }
          }
@ -504,11 +642,12 @@ static void protocol_exec_rt_suspend()
            #ifdef PARKING_ENABLE
              // Execute fast restore motion to the pull-out position. Parking requires homing enabled.
              // NOTE: State is will remain DOOR, until the de-energizing and retract is complete.
-            if (bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE)) {
+              if ((settings.flags & (BITFLAG_HOMING_ENABLE|BITFLAG_LASER_MODE)) == BITFLAG_HOMING_ENABLE) {
                // Check to ensure the motion doesn't move below pull-out position.
                if (parking_target[PARKING_AXIS] <= PARKING_TARGET) {
                  parking_target[PARKING_AXIS] = retract_waypoint;
-                mc_parking_motion(parking_target, PARKING_RATE);
+                  pl_data->feed_rate = PARKING_RATE;
                  mc_parking_motion(parking_target, pl_data);
                }
              }
            #endif
@ -517,27 +656,34 @@ static void protocol_exec_rt_suspend()
            if (gc_state.modal.spindle != SPINDLE_DISABLE) {
              // Block if safety door re-opened during prior restore actions.
              if (bit_isfalse(sys.suspend,SUSPEND_RESTART_RETRACT)) {
-              spindle_set_state(gc_state.modal.spindle, gc_state.spindle_speed); 
+                if (bit_istrue(settings.flags,BITFLAG_LASER_MODE)) {
-              delay_sec(SAFETY_DOOR_SPINDLE_DELAY, DELAY_MODE_SAFETY_DOOR);
+                  // When in laser mode, ignore spindle spin-up delay. Set to turn on laser when cycle starts.
                  bit_true(sys.step_control, STEP_CONTROL_UPDATE_SPINDLE_PWM);
                } else {
                  spindle_set_state((restore_condition & (PL_COND_FLAG_SPINDLE_CW | PL_COND_FLAG_SPINDLE_CCW)), restore_spindle_speed);
                  delay_sec(SAFETY_DOOR_SPINDLE_DELAY, DELAY_MODE_SYS_SUSPEND);
                }
              }
            }
            if (gc_state.modal.coolant != COOLANT_DISABLE) {
              // Block if safety door re-opened during prior restore actions.
              if (bit_isfalse(sys.suspend,SUSPEND_RESTART_RETRACT)) {
-              coolant_set_state(gc_state.modal.coolant); 
+                // NOTE: Laser mode will honor this delay. An exhaust system is often controlled by this pin.
-              delay_sec(SAFETY_DOOR_COOLANT_DELAY, DELAY_MODE_SAFETY_DOOR);
+                coolant_set_state((restore_condition & (PL_COND_FLAG_COOLANT_FLOOD | PL_COND_FLAG_COOLANT_FLOOD)));
                delay_sec(SAFETY_DOOR_COOLANT_DELAY, DELAY_MODE_SYS_SUSPEND);
              }
            }
            #ifdef PARKING_ENABLE
              // Execute slow plunge motion from pull-out position to resume position.
-            if (bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE)) {
+              if ((settings.flags & (BITFLAG_HOMING_ENABLE|BITFLAG_LASER_MODE)) == BITFLAG_HOMING_ENABLE) {
                // Block if safety door re-opened during prior restore actions.
                if (bit_isfalse(sys.suspend,SUSPEND_RESTART_RETRACT)) {
                  // Regardless if the retract parking motion was a valid/safe motion or not, the
                  // restore parking motion should logically be valid, either by returning to the
                  // original position through valid machine space or by not moving at all.
-                mc_parking_motion(restore_target, PARKING_PULLOUT_RATE);
+                  pl_data->feed_rate = PARKING_PULLOUT_RATE;
                  mc_parking_motion(restore_target, pl_data);
                }
              }
            #endif
@ -549,8 +695,43 @@ static void protocol_exec_rt_suspend()
          }
        }
      } else {
        // Feed hold manager. Controls spindle stop override states.
        // NOTE: Hold ensured as completed by condition check at the beginning of suspend routine.
        if (sys.toggle_ovr_mask & TOGGLE_OVR_STOP_INITIATE) { // Handles beginning of spindle stop
          bit_false(sys.toggle_ovr_mask,TOGGLE_OVR_STOP_ACTIVE_MASK); // Clear stop override state
          if (gc_state.modal.spindle != SPINDLE_DISABLE) {
            spindle_stop(); // De-energize
            sys.toggle_ovr_mask |= TOGGLE_OVR_STOP_ENABLED; // Set stop override state to enabled, if de-energized.
          }
        } else if (sys.toggle_ovr_mask & (TOGGLE_OVR_STOP_RESTORE | TOGGLE_OVR_STOP_RESTORE_CYCLE)) { // Handles restoring of spindle state
          if (gc_state.modal.spindle != SPINDLE_DISABLE) {
            report_feedback_message(MESSAGE_SPINDLE_RESTORE);
            if (bit_istrue(settings.flags,BITFLAG_LASER_MODE)) {
              // When in laser mode, ignore spindle spin-up delay. Set to turn on laser when cycle starts.
              bit_true(sys.step_control, STEP_CONTROL_UPDATE_SPINDLE_PWM);
            } else {
              spindle_set_state((restore_condition & (PL_COND_FLAG_SPINDLE_CW | PL_COND_FLAG_SPINDLE_CCW)), restore_spindle_speed);
              delay_sec(SAFETY_DOOR_SPINDLE_DELAY, DELAY_MODE_SYS_SUSPEND);
            }
          }
          if (sys.toggle_ovr_mask & TOGGLE_OVR_STOP_RESTORE_CYCLE) {
            system_set_exec_state_flag(EXEC_CYCLE_START);  // Set to resume program.
          }
          bit_false(sys.toggle_ovr_mask,TOGGLE_OVR_STOP_ACTIVE_MASK); // Clear stop override state
        }
      }
    }
    protocol_exec_rt_system();
  }
 }
--- a/grbl/protocol.h
+++ b/grbl/protocol.h
@ -2,7 +2,7 @@
  protocol.h - controls Grbl execution protocol and procedures
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -40,15 +40,6 @@ void protocol_main_loop();
 void protocol_execute_realtime();
 void protocol_exec_rt_system();
 // Notify the stepper subsystem to start executing the g-code program in buffer.
 // void protocol_cycle_start();
 // Reinitializes the buffer after a feed hold for a resume.
 // void protocol_cycle_reinitialize(); 
 // Initiates a feed hold of the running program
 // void protocol_feed_hold();
 // Executes the auto cycle feature, if enabled.
 void protocol_auto_cycle_start();
--- a/grbl/report.c
+++ b/grbl/report.c
@ -2,7 +2,7 @@
  report.c - reporting and messaging methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon  
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -29,23 +29,98 @@
 #include "grbl.h"
 // Internal report utilities to reduce flash with repetitive tasks turned into functions.
 void report_util_setting_prefix(uint8_t n) { serial_write('$'); print_uint8_base10(n); serial_write('='); }
 static void report_util_line_feed() { printPgmString(PSTR("\r\n")); }
 static void report_util_feedback_line_feed() { serial_write(']'); report_util_line_feed(); }
 // static void report_util_comment_line_feed() { serial_write(')'); report_util_line_feed(); }
 static void report_util_axis_values(float *axis_value) {
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    printFloat_CoordValue(axis_value[idx]);
    if (idx < (N_AXIS-1)) { serial_write(','); }
  }
 }
 // static void report_util_setting_string(uint8_t n) {
 //   serial_write(' ');
 //   serial_write('(');
 //   switch(n) {
 //     case 0: printPgmString(PSTR("stp pulse:us")); break;
 //     case 1: printPgmString(PSTR("idl delay:ms")); break; 
 //     case 2: printPgmString(PSTR("stp inv:msk")); break;
 //     case 3: printPgmString(PSTR("dir inv:msk")); break;
 //     case 4: printPgmString(PSTR("stp enbl inv")); break;
 //     case 5: printPgmString(PSTR("lim inv")); break;
 //     case 6: printPgmString(PSTR("prb inv")); break;
 //     case 10: printPgmString(PSTR("rpt:msk")); break;
 //     case 11: printPgmString(PSTR("jnc dev:mm")); break;
 //     case 12: printPgmString(PSTR("arc tol:mm")); break;
 //     case 13: printPgmString(PSTR("rpt inch")); break;
 //     case 20: printPgmString(PSTR("sft lim")); break;
 //     case 21: printPgmString(PSTR("hrd lim")); break;
 //     case 22: printPgmString(PSTR("hm cyc")); break;
 //     case 23: printPgmString(PSTR("hm dir inv:msk")); break;
 //     case 24: printPgmString(PSTR("hm feed:mm/min")); break;
 //     case 25: printPgmString(PSTR("hm seek:mm/min")); break;
 //     case 26: printPgmString(PSTR("hm delay:ms")); break;
 //     case 27: printPgmString(PSTR("hm off:mm")); break;
 //     case 30: printPgmString(PSTR("rpm max")); break;
 //     case 31: printPgmString(PSTR("rpm min")); break;
 //     case 32: printPgmString(PSTR("laser")); break;
 //     default:
 //       n -= AXIS_SETTINGS_START_VAL;
 //       uint8_t idx = 0;
 //       while (n < 10) {
 //         if (n<10) {
 //           print_uint8_base10(n+idx);
 //           switch (idx) {
 //             case 0: printPgmString(PSTR(":stp/mm")); break;
 //             case 1: printPgmString(PSTR(":mm/min")); break;
 //             case 2: printPgmString(PSTR(":mm/s^2")); break;
 //             case 3: printPgmString(PSTR(":mm max")); break;
 //           }
 //         } else {
 //           n -= 10;
 //           idx++;
 //         }
 //       }
 //   }
 //   report_util_comment_line_feed();
 // }
 static void report_util_uint8_setting(uint8_t n, int val) { 
  report_util_setting_prefix(n); 
  print_uint8_base10(val); 
  report_util_line_feed();
 //   report_util_setting_string(n); 
 }
 static void report_util_float_setting(uint8_t n, float val, uint8_t n_decimal) { 
  report_util_setting_prefix(n); 
  printFloat(val,n_decimal);
  report_util_line_feed();
 //   report_util_setting_string(n);
 }
 // Handles the primary confirmation protocol response for streaming interfaces and human-feedback.
 // For every incoming line, this method responds with an 'ok' for a successful command or an
 // 'error:'  to indicate some error event with the line or some critical system error during
 // operation. Errors events can originate from the g-code parser, settings module, or asynchronously
 // from a critical error, such as a triggered hard limit. Interface should always monitor for these
 // responses.
-// NOTE: In silent mode, all error codes are greater than zero.
+// NOTE: In REPORT_GUI_MODE, all error codes are greater than zero.
 // TODO: Install silent mode to return only numeric values, primarily for GUIs.
 void report_status_message(uint8_t status_code)
 {
-  if (status_code == 0) { // STATUS_OK
+  switch(status_code) {
-    printPgmString(PSTR("ok\r\n"));
+    case STATUS_OK: // STATUS_OK
-  } else {
+      printPgmString(PSTR("ok\r\n")); break;
-    printPgmString(PSTR("error: "));
+    default:
      #ifdef REPORT_GUI_MODE
        printPgmString(PSTR("error:"));
        print_uint8_base10(status_code);
      #else
        printPgmString(PSTR("error: "));
        switch(status_code) {
          case STATUS_EXPECTED_COMMAND_LETTER:
            printPgmString(PSTR("Expected command letter")); break;
@ -63,8 +138,8 @@ void report_status_message(uint8_t status_code)
            printPgmString(PSTR("EEPROM read fail. Using defaults")); break;
          case STATUS_IDLE_ERROR:
            printPgmString(PSTR("Not idle")); break;
-        case STATUS_ALARM_LOCK:
+          case STATUS_SYSTEM_GC_LOCK:
-        printPgmString(PSTR("Alarm lock")); break;
+            printPgmString(PSTR("G-code lock")); break;
          case STATUS_SOFT_LIMIT_ERROR:
            printPgmString(PSTR("Homing not enabled")); break;
          case STATUS_OVERFLOW:
@ -75,11 +150,17 @@ void report_status_message(uint8_t status_code)
          #endif
          case STATUS_CHECK_DOOR:
            printPgmString(PSTR("Check Door")); break;
          // case STATUS_LINE_LENGTH_EXCEEDED: // Supported on Grbl-Mega only.
          //  printPgmString(PSTR("Line length exceeded")); break;
          case STATUS_TRAVEL_EXCEEDED:
            printPgmString(PSTR("Travel exceeded")); break;
          case STATUS_INVALID_JOG_COMMAND:
            printPgmString(PSTR("Invalid jog command")); break;
          // Common g-code parser errors.
        case STATUS_GCODE_MODAL_GROUP_VIOLATION:
        printPgmString(PSTR("Modal group violation")); break;
          case STATUS_GCODE_UNSUPPORTED_COMMAND:
            printPgmString(PSTR("Unsupported command")); break;
          case STATUS_GCODE_MODAL_GROUP_VIOLATION:
            printPgmString(PSTR("Modal group violation")); break;
          case STATUS_GCODE_UNDEFINED_FEED_RATE:
            printPgmString(PSTR("Undefined feed rate")); break;
          default:
@ -88,17 +169,18 @@ void report_status_message(uint8_t status_code)
            print_uint8_base10(status_code); // Print error code for user reference
        }
      #endif
-    printPgmString(PSTR("\r\n"));
+      report_util_line_feed();
  }
 }
 // Prints alarm messages.
 void report_alarm_message(int8_t alarm_code)
 {
  printPgmString(PSTR("ALARM: "));
  #ifdef REPORT_GUI_MODE
    printPgmString(PSTR("ALARM:"));
    print_uint8_base10(alarm_code);
  #else
    printPgmString(PSTR("ALARM: "));
    switch (alarm_code) {
      case ALARM_HARD_LIMIT_ERROR:
        printPgmString(PSTR("Hard limit")); break;
@ -106,13 +188,17 @@ void report_alarm_message(int8_t alarm_code)
        printPgmString(PSTR("Soft limit")); break;
      case ALARM_ABORT_CYCLE:
        printPgmString(PSTR("Abort during cycle")); break;
-      case ALARM_PROBE_FAIL:
+      case ALARM_PROBE_FAIL_INITIAL:
      case ALARM_PROBE_FAIL_CONTACT:
        printPgmString(PSTR("Probe fail")); break;
-      case ALARM_HOMING_FAIL:
+      case ALARM_HOMING_FAIL_RESET:
      case ALARM_HOMING_FAIL_DOOR:
      case ALARM_HOMING_FAIL_PULLOFF:
      case ALARM_HOMING_FAIL_APPROACH:
        printPgmString(PSTR("Homing fail")); break;
    }
  #endif
-  printPgmString(PSTR("\r\n"));
+  report_util_line_feed();
  delay_ms(500); // Force delay to ensure message clears serial write buffer.
 }
@ -121,10 +207,9 @@ void report_alarm_message(int8_t alarm_code)
 // messages such as setup warnings, switch toggling, and how to exit alarms.
 // NOTE: For interfaces, messages are always placed within brackets. And if silent mode
 // is installed, the message number codes are less than zero.
 // TODO: Install silence feedback messages option in settings
 void report_feedback_message(uint8_t message_code)
 {
-  printPgmString(PSTR("["));
+  printPgmString(PSTR("[MSG:"));
  switch(message_code) {
    case MESSAGE_CRITICAL_EVENT:
      printPgmString(PSTR("Reset to continue")); break;
@ -138,12 +223,18 @@ void report_feedback_message(uint8_t message_code)
      printPgmString(PSTR("Disabled")); break;
    case MESSAGE_SAFETY_DOOR_AJAR:
      printPgmString(PSTR("Check Door")); break;
    case MESSAGE_CHECK_LIMITS:
      printPgmString(PSTR("Check Limits")); break;
    case MESSAGE_PROGRAM_END:
      printPgmString(PSTR("Pgm End")); break;
    case MESSAGE_RESTORE_DEFAULTS:
      printPgmString(PSTR("Restoring defaults")); break;
    case MESSAGE_SPINDLE_RESTORE:
      printPgmString(PSTR("Restoring spindle")); break;
    case MESSAGE_SLEEP_MODE:
      printPgmString(PSTR("Sleeping")); break;
  }
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
 }
@ -155,7 +246,9 @@ void report_init_message()
 // Grbl help message
 void report_grbl_help() {
-  #ifndef REPORT_GUI_MODE
+  #ifdef REPORT_GUI_MODE
    printPgmString(PSTR("[HLP:$$ $# $G $I $N $x=val $Nx=line $J=line $SLP $C $X $H ~ ! ? ctrl-x]\r\n"));
  #else
    printPgmString(PSTR("$$ (view Grbl settings)\r\n"
                        "$# (view # parameters)\r\n"
                        "$G (view parser state)\r\n"
@ -163,6 +256,8 @@ void report_grbl_help() {
                        "$N (view startup blocks)\r\n"
                        "$x=value (save Grbl setting)\r\n"
                        "$Nx=line (save startup block)\r\n"
                        "$J=line (jog)\r\n"
                        "$SLP (sleep mode)\r\n"
                        "$C (check gcode mode)\r\n"
                        "$X (kill alarm lock)\r\n"
                        "$H (run homing cycle)\r\n"
@ -179,75 +274,93 @@ void report_grbl_help() {
 void report_grbl_settings() {
  // Print Grbl settings.
  #ifdef REPORT_GUI_MODE
-    printPgmString(PSTR("$0=")); print_uint8_base10(settings.pulse_microseconds);
+
-    printPgmString(PSTR("\r\n$1=")); print_uint8_base10(settings.stepper_idle_lock_time);
+    report_util_uint8_setting(0,settings.pulse_microseconds);
-    printPgmString(PSTR("\r\n$2=")); print_uint8_base10(settings.step_invert_mask); 
+    report_util_uint8_setting(1,settings.stepper_idle_lock_time);
-    printPgmString(PSTR("\r\n$3=")); print_uint8_base10(settings.dir_invert_mask); 
+    report_util_uint8_setting(2,settings.step_invert_mask);
-    printPgmString(PSTR("\r\n$4=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE));
+    report_util_uint8_setting(3,settings.dir_invert_mask);
-    printPgmString(PSTR("\r\n$5=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS));
+    report_util_uint8_setting(4,bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE));
-    printPgmString(PSTR("\r\n$6=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_PROBE_PIN));
+    report_util_uint8_setting(5,bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS));
-    printPgmString(PSTR("\r\n$10=")); print_uint8_base10(settings.status_report_mask);
+    report_util_uint8_setting(6,bit_istrue(settings.flags,BITFLAG_INVERT_PROBE_PIN));
-    printPgmString(PSTR("\r\n$11=")); printFloat_SettingValue(settings.junction_deviation);
+    report_util_uint8_setting(10,settings.status_report_mask);
-    printPgmString(PSTR("\r\n$12=")); printFloat_SettingValue(settings.arc_tolerance);
+    report_util_float_setting(11,settings.junction_deviation,N_DECIMAL_SETTINGVALUE);
-    printPgmString(PSTR("\r\n$13=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_REPORT_INCHES));
+    report_util_float_setting(12,settings.arc_tolerance,N_DECIMAL_SETTINGVALUE);
-    printPgmString(PSTR("\r\n$20=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE));
+    report_util_uint8_setting(13,bit_istrue(settings.flags,BITFLAG_REPORT_INCHES));
-    printPgmString(PSTR("\r\n$21=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE));
+    report_util_uint8_setting(20,bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE));
-    printPgmString(PSTR("\r\n$22=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE));
+    report_util_uint8_setting(21,bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE));
-    printPgmString(PSTR("\r\n$23=")); print_uint8_base10(settings.homing_dir_mask);
+    report_util_uint8_setting(22,bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE));
-    printPgmString(PSTR("\r\n$24=")); printFloat_SettingValue(settings.homing_feed_rate);
+    report_util_uint8_setting(23,settings.homing_dir_mask);
-    printPgmString(PSTR("\r\n$25=")); printFloat_SettingValue(settings.homing_seek_rate);
+    report_util_float_setting(24,settings.homing_feed_rate,N_DECIMAL_SETTINGVALUE);
-    printPgmString(PSTR("\r\n$26=")); print_uint8_base10(settings.homing_debounce_delay);
+    report_util_float_setting(25,settings.homing_seek_rate,N_DECIMAL_SETTINGVALUE);
-    printPgmString(PSTR("\r\n$27=")); printFloat_SettingValue(settings.homing_pulloff);
+    report_util_uint8_setting(26,settings.homing_debounce_delay);
-    printPgmString(PSTR("\r\n$30=")); printFloat_RPMValue(settings.rpm_max);
+    report_util_float_setting(27,settings.homing_pulloff,N_DECIMAL_SETTINGVALUE);
-    printPgmString(PSTR("\r\n$31=")); printFloat_RPMValue(settings.rpm_min);
+    report_util_float_setting(30,settings.rpm_max,N_DECIMAL_RPMVALUE);
-    printPgmString(PSTR("\r\n"));
+    report_util_float_setting(31,settings.rpm_min,N_DECIMAL_RPMVALUE);
    #ifdef VARIABLE_SPINDLE
      report_util_uint8_setting(32,bit_istrue(settings.flags,BITFLAG_LASER_MODE));
    #else
      report_util_uint8_setting(32,0);
    #endif
    // Print axis settings
    uint8_t idx, set_idx;
    uint8_t val = AXIS_SETTINGS_START_VAL;
    for (set_idx=0; set_idx<AXIS_N_SETTINGS; set_idx++) {
      for (idx=0; idx<N_AXIS; idx++) {
        switch (set_idx) {
          case 0: report_util_float_setting(val+idx,settings.steps_per_mm[idx],N_DECIMAL_SETTINGVALUE); break;
          case 1: report_util_float_setting(val+idx,settings.max_rate[idx],N_DECIMAL_SETTINGVALUE); break;
          case 2: report_util_float_setting(val+idx,settings.acceleration[idx]/(60*60),N_DECIMAL_SETTINGVALUE); break;
          case 3: report_util_float_setting(val+idx,-settings.max_travel[idx],N_DECIMAL_SETTINGVALUE); break;
        }
      }
      val += AXIS_SETTINGS_INCREMENT;
    }
  #else
    printPgmString(PSTR("$0=")); print_uint8_base10(settings.pulse_microseconds);
    printPgmString(PSTR(" (step pulse, usec)\r\n$1=")); print_uint8_base10(settings.stepper_idle_lock_time);
    printPgmString(PSTR(" (step idle delay, msec)\r\n$2=")); print_uint8_base10(settings.step_invert_mask);
-    printPgmString(PSTR(" (step port invert mask:")); print_uint8_base2(settings.step_invert_mask);  
+    printPgmString(PSTR(" (step port invert mask)\r\n$3=")); print_uint8_base10(settings.dir_invert_mask);
-    printPgmString(PSTR(")\r\n$3=")); print_uint8_base10(settings.dir_invert_mask); 
+    printPgmString(PSTR(" (dir port invert mask)\r\n$4=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE));
    printPgmString(PSTR(" (dir port invert mask:")); print_uint8_base2(settings.dir_invert_mask);  
    printPgmString(PSTR(")\r\n$4=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE));
    printPgmString(PSTR(" (step enable invert, bool)\r\n$5=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS));
    printPgmString(PSTR(" (limit pins invert, bool)\r\n$6=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_INVERT_PROBE_PIN));
    printPgmString(PSTR(" (probe pin invert, bool)\r\n$10=")); print_uint8_base10(settings.status_report_mask);
-    printPgmString(PSTR(" (status report mask:")); print_uint8_base2(settings.status_report_mask);
+    printPgmString(PSTR(" (status report mask)\r\n$11=")); printFloat_SettingValue(settings.junction_deviation);
    printPgmString(PSTR(")\r\n$11=")); printFloat_SettingValue(settings.junction_deviation);
    printPgmString(PSTR(" (junction deviation, mm)\r\n$12=")); printFloat_SettingValue(settings.arc_tolerance);
    printPgmString(PSTR(" (arc tolerance, mm)\r\n$13=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_REPORT_INCHES));
    printPgmString(PSTR(" (report inches, bool)\r\n$20=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_SOFT_LIMIT_ENABLE));
    printPgmString(PSTR(" (soft limits, bool)\r\n$21=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_HARD_LIMIT_ENABLE));
    printPgmString(PSTR(" (hard limits, bool)\r\n$22=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_HOMING_ENABLE));
    printPgmString(PSTR(" (homing cycle, bool)\r\n$23=")); print_uint8_base10(settings.homing_dir_mask);
-    printPgmString(PSTR(" (homing dir invert mask:")); print_uint8_base2(settings.homing_dir_mask);  
+    printPgmString(PSTR(" (homing dir invert mask\r\n$24=")); printFloat_SettingValue(settings.homing_feed_rate);
    printPgmString(PSTR(")\r\n$24=")); printFloat_SettingValue(settings.homing_feed_rate);
    printPgmString(PSTR(" (homing feed, mm/min)\r\n$25=")); printFloat_SettingValue(settings.homing_seek_rate);
    printPgmString(PSTR(" (homing seek, mm/min)\r\n$26=")); print_uint8_base10(settings.homing_debounce_delay);
    printPgmString(PSTR(" (homing debounce, msec)\r\n$27=")); printFloat_SettingValue(settings.homing_pulloff);
    printPgmString(PSTR(" (homing pull-off, mm)\r\n$30=")); printFloat_RPMValue(settings.rpm_max);
    printPgmString(PSTR(" (rpm max)\r\n$31=")); printFloat_RPMValue(settings.rpm_min);
-    printPgmString(PSTR(" (rpm min)\r\n"));
+    #ifdef VARIABLE_SPINDLE
      printPgmString(PSTR(" (rpm min)\r\n$32=")); print_uint8_base10(bit_istrue(settings.flags,BITFLAG_LASER_MODE));
      printPgmString(PSTR(" (laser mode, bool)\r\n"));
    #else
      printPgmString(PSTR(" (rpm min)\r\n$32=0 (laser mode, bool)\r\n"));
    #endif
    // Print axis settings
    uint8_t idx, set_idx;
    uint8_t val = AXIS_SETTINGS_START_VAL;
    for (set_idx=0; set_idx<AXIS_N_SETTINGS; set_idx++) {
      for (idx=0; idx<N_AXIS; idx++) {
-      printPgmString(PSTR("$"));
+        serial_write('$');
        print_uint8_base10(val+idx);
-      printPgmString(PSTR("="));
+        serial_write('=');
        switch (set_idx) {
          case 0: printFloat_SettingValue(settings.steps_per_mm[idx]); break;
          case 1: printFloat_SettingValue(settings.max_rate[idx]); break;
          case 2: printFloat_SettingValue(settings.acceleration[idx]/(60*60)); break;
          case 3: printFloat_SettingValue(-settings.max_travel[idx]); break;
        }
-      #ifdef REPORT_GUI_MODE
+        serial_write(' ');
-        printPgmString(PSTR("\r\n"));
+        serial_write('(');
      #else
        printPgmString(PSTR(" ("));
        switch (idx) {
          case X_AXIS: printPgmString(PSTR("x")); break;
          case Y_AXIS: printPgmString(PSTR("y")); break;
@ -260,10 +373,11 @@ void report_grbl_settings() {
          case 3: printPgmString(PSTR(" max travel, mm")); break;
        }
        printPgmString(PSTR(")\r\n"));
      #endif
      }
      val += AXIS_SETTINGS_INCREMENT;
    }
  #endif
 }
@ -272,19 +386,14 @@ void report_grbl_settings() {
 // These values are retained until Grbl is power-cycled, whereby they will be re-zeroed.
 void report_probe_parameters()
 {
  uint8_t i;
  float print_position[N_AXIS];
  // Report in terms of machine position.
  printPgmString(PSTR("[PRB:"));
-  for (i=0; i< N_AXIS; i++) {
+  float print_position[N_AXIS];
-    print_position[i] = system_convert_axis_steps_to_mpos(sys.probe_position,i);
+  system_convert_array_steps_to_mpos(print_position,sys_probe_position);
-    printFloat_CoordValue(print_position[i]);
+  report_util_axis_values(print_position);
-    if (i < (N_AXIS-1)) { printPgmString(PSTR(",")); }
+  serial_write(':');
  }
  printPgmString(PSTR(":"));
  print_uint8_base10(sys.probe_succeeded);
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
 }
@ -292,7 +401,7 @@ void report_probe_parameters()
 void report_ngc_parameters()
 {
  float coord_data[N_AXIS];
-  uint8_t coord_select, i;
+  uint8_t coord_select;
  for (coord_select = 0; coord_select <= SETTING_INDEX_NCOORD; coord_select++) {
    if (!(settings_read_coord_data(coord_select,coord_data))) {
      report_status_message(STATUS_SETTING_READ_FAIL);
@ -304,22 +413,16 @@ void report_ngc_parameters()
      case 7: printPgmString(PSTR("30")); break;
      default: print_uint8_base10(coord_select+54); break; // G54-G59
    }
-    printPgmString(PSTR(":"));         
+    serial_write(':');
-    for (i=0; i<N_AXIS; i++) {
+    report_util_axis_values(coord_data);
-      printFloat_CoordValue(coord_data[i]);
+    report_util_feedback_line_feed();
      if (i < (N_AXIS-1)) { printPgmString(PSTR(",")); }
      else { printPgmString(PSTR("]\r\n")); }
    } 
  }
  printPgmString(PSTR("[G92:")); // Print G92,G92.1 which are not persistent in memory
-  for (i=0; i<N_AXIS; i++) {
+  report_util_axis_values(gc_state.coord_offset);
-    printFloat_CoordValue(gc_state.coord_offset[i]);
+  report_util_feedback_line_feed();
    if (i < (N_AXIS-1)) { printPgmString(PSTR(",")); }
    else { printPgmString(PSTR("]\r\n")); }
  } 
  printPgmString(PSTR("[TLO:")); // Print tool length offset value
  printFloat_CoordValue(gc_state.tool_length_offset);
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
  report_probe_parameters(); // Print probe parameters. Not persistent in memory.
 }
@ -327,56 +430,64 @@ void report_ngc_parameters()
 // Print current gcode parser mode state
 void report_gcode_modes()
 {
-  printPgmString(PSTR("["));
+  printPgmString(PSTR("[GC:G"));
  switch (gc_state.modal.motion) {
-    case MOTION_MODE_SEEK : printPgmString(PSTR("G0")); break;
+    case MOTION_MODE_SEEK : serial_write('0'); break;
-    case MOTION_MODE_LINEAR : printPgmString(PSTR("G1")); break;
+    case MOTION_MODE_LINEAR : serial_write('1'); break;
-    case MOTION_MODE_CW_ARC : printPgmString(PSTR("G2")); break;
+    case MOTION_MODE_CW_ARC : serial_write('2'); break;
-    case MOTION_MODE_CCW_ARC : printPgmString(PSTR("G3")); break;
+    case MOTION_MODE_CCW_ARC : serial_write('3'); break;
-    case MOTION_MODE_NONE : printPgmString(PSTR("G80")); break;
+    case MOTION_MODE_NONE : printPgmString(PSTR("80")); break;
    default:
-      printPgmString(PSTR("G38."));
+      printPgmString(PSTR("38."));
      print_uint8_base10(gc_state.modal.motion - (MOTION_MODE_PROBE_TOWARD-2));
  }
  printPgmString(PSTR(" G"));
  print_uint8_base10(gc_state.modal.coord_select+54);
  printPgmString(PSTR(" G1"));
  switch (gc_state.modal.plane_select) {
-    case PLANE_SELECT_XY : printPgmString(PSTR(" G17")); break;
+    case PLANE_SELECT_XY : serial_write('7'); break;
-    case PLANE_SELECT_ZX : printPgmString(PSTR(" G18")); break;
+    case PLANE_SELECT_ZX : serial_write('8'); break;
-    case PLANE_SELECT_YZ : printPgmString(PSTR(" G19")); break;
+    case PLANE_SELECT_YZ : serial_write('9'); break;
  }
-  if (gc_state.modal.units == UNITS_MODE_MM) { printPgmString(PSTR(" G21")); }
+  printPgmString(PSTR(" G2"));
-  else { printPgmString(PSTR(" G20")); }
+  if (gc_state.modal.units == UNITS_MODE_MM) { serial_write('1'); }
  else { serial_write('0'); }
-  if (gc_state.modal.distance == DISTANCE_MODE_ABSOLUTE) { printPgmString(PSTR(" G90")); }
+  printPgmString(PSTR(" G9"));
-  else { printPgmString(PSTR(" G91")); }
+  if (gc_state.modal.distance == DISTANCE_MODE_ABSOLUTE) { serial_write('0'); }
  else { serial_write('1'); }
-  if (gc_state.modal.feed_rate == FEED_RATE_MODE_INVERSE_TIME) { printPgmString(PSTR(" G93")); }
+  printPgmString(PSTR(" G9"));
-  else { printPgmString(PSTR(" G94")); }
+  if (gc_state.modal.feed_rate == FEED_RATE_MODE_INVERSE_TIME) { serial_write('3'); }
  else { serial_write('4'); }
  printPgmString(PSTR(" M"));
  switch (gc_state.modal.program_flow) {
-    case PROGRAM_FLOW_RUNNING : printPgmString(PSTR(" M0")); break;
+    case PROGRAM_FLOW_RUNNING : serial_write('0'); break;
-    case PROGRAM_FLOW_PAUSED : printPgmString(PSTR(" M1")); break;
+    case PROGRAM_FLOW_PAUSED : serial_write('1'); break;
-    case PROGRAM_FLOW_COMPLETED : printPgmString(PSTR(" M2")); break;
+    case PROGRAM_FLOW_COMPLETED : serial_write('2'); break;
  }
  printPgmString(PSTR(" M"));
  switch (gc_state.modal.spindle) {
-    case SPINDLE_ENABLE_CW : printPgmString(PSTR(" M3")); break;
+    case SPINDLE_ENABLE_CW : serial_write('3'); break;
-    case SPINDLE_ENABLE_CCW : printPgmString(PSTR(" M4")); break;
+    case SPINDLE_ENABLE_CCW : serial_write('4'); break;
-    case SPINDLE_DISABLE : printPgmString(PSTR(" M5")); break;
+    case SPINDLE_DISABLE : serial_write('5'); break;
  }
-  switch (gc_state.modal.coolant) {
+  printPgmString(PSTR(" M"));
    case COOLANT_DISABLE : printPgmString(PSTR(" M9")); break;
    case COOLANT_FLOOD_ENABLE : printPgmString(PSTR(" M8")); break;
  #ifdef ENABLE_M7
-      case COOLANT_MIST_ENABLE : printPgmString(PSTR(" M7")); break;
+    if (gc_state.modal.coolant) { // Note: Multiple coolant states may be active at the same time.
      if (gc_state.modal.coolant & PL_COND_FLAG_COOLANT_MIST) { serial_write('7'); }
      if (gc_state.modal.coolant & PL_COND_FLAG_COOLANT_FLOOD) { serial_write('8'); }
    } else { serial_write('9'); }
  #else
    if (gc_state.modal.coolant) { serial_write('8'); }
    else { serial_write('9'); }
  #endif
  }
  printPgmString(PSTR(" T"));
  print_uint8_base10(gc_state.tool);
@ -386,27 +497,36 @@ void report_gcode_modes()
  #ifdef VARIABLE_SPINDLE
    printPgmString(PSTR(" S"));
-    printFloat_RPMValue(gc_state.spindle_speed);
+    printFloat(gc_state.spindle_speed,N_DECIMAL_RPMVALUE);
  #endif
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
 }
 // Prints specified startup line
 void report_startup_line(uint8_t n, char *line)
 {
-  printPgmString(PSTR("$N")); print_uint8_base10(n);
+  printPgmString(PSTR("$N"));
-  printPgmString(PSTR("=")); printString(line);
+  print_uint8_base10(n);
-  printPgmString(PSTR("\r\n"));
+  serial_write('=');
  printString(line);
  report_util_line_feed();
 }
 void report_execute_startup_message(char *line, uint8_t status_code)
 {
  serial_write('>');
  printString(line);
  serial_write(':');
  report_status_message(status_code);
 }
 // Prints build info line
 void report_build_info(char *line)
 {
-  printPgmString(PSTR("[" GRBL_VERSION "." GRBL_VERSION_BUILD ":"));
+  printPgmString(PSTR("[VER:" GRBL_VERSION "." GRBL_VERSION_BUILD ":"));
  printString(line);
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
 }
@ -415,7 +535,7 @@ void report_build_info(char *line)
 void report_echo_line_received(char *line)
 {
  printPgmString(PSTR("[echo: ")); printString(line);
-  printPgmString(PSTR("]\r\n"));
+  report_util_feedback_line_feed();
 }
@ -426,25 +546,35 @@ void report_echo_line_received(char *line)
 // especially during g-code programs with fast, short line segments and high frequency reports (5-20Hz).
 void report_realtime_status()
 {
-  // **Under construction** Bare-bones status report. Provides real-time machine position relative to 
+  #ifdef USE_CLASSIC_REALTIME_REPORT
-  // the system power on location (0,0,0) and work coordinate position (G54 and G92 applied). Eventually
+
  // to be added are distance to go on block, processed block id, and feed rate. Also a settings bitmask
  // for a user to select the desired real-time data.
    uint8_t idx;
    int32_t current_position[N_AXIS]; // Copy current state of the system position variable
-  memcpy(current_position,sys.position,sizeof(sys.position));
+    memcpy(current_position,sys_position,sizeof(sys_position));
    float print_position[N_AXIS];
    // Report current machine state
    switch (sys.state) {
      case STATE_IDLE: printPgmString(PSTR("<Idle")); break;
    case STATE_MOTION_CANCEL: // Report run state.
      case STATE_CYCLE: printPgmString(PSTR("<Run")); break;
-    case STATE_HOLD: printPgmString(PSTR("<Hold")); break;
+      case STATE_HOLD:
        if (!(sys.suspend & SUSPEND_JOG_CANCEL)) {
          printPgmString(PSTR("<Hold"));
          break;
        } // Continues to print jog state during jog cancel.
      case STATE_JOG: printPgmString(PSTR("<Jog")); break;
      case STATE_HOMING: printPgmString(PSTR("<Home")); break;
      case STATE_ALARM: printPgmString(PSTR("<Alarm")); break;
      case STATE_CHECK_MODE: printPgmString(PSTR("<Check")); break;
-    case STATE_SAFETY_DOOR: printPgmString(PSTR("<Door")); break;
+      case STATE_SAFETY_DOOR:
        if (!(sys.suspend & SUSPEND_RETRACT_COMPLETE)) {
          printPgmString(PSTR("<Door"));
        } else {
          if (sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) { printPgmString(PSTR("<Door")); }
          else { printPgmString(PSTR("<Hold")); }
        }
        break;
      case STATE_SLEEP: printPgmString(PSTR("<Sleep")); break;        
    }
    // If reporting a position, convert the current step count (current_position) to millimeters.
@ -457,7 +587,7 @@ void report_realtime_status()
      printPgmString(PSTR(",MPos:"));
      for (idx=0; idx< N_AXIS; idx++) {
        printFloat_CoordValue(print_position[idx]);
-      if (idx < (N_AXIS-1)) { printPgmString(PSTR(",")); }
+        if (idx < (N_AXIS-1)) { serial_write(','); }
      }
    }
@ -469,7 +599,7 @@ void report_realtime_status()
        print_position[idx] -= gc_state.coord_system[idx]+gc_state.coord_offset[idx];
        if (idx == TOOL_LENGTH_OFFSET_AXIS) { print_position[idx] -= gc_state.tool_length_offset; }
        printFloat_CoordValue(print_position[idx]);
-      if (idx < (N_AXIS-1)) { printPgmString(PSTR(",")); }
+        if (idx < (N_AXIS-1)) { serial_write(','); }
      }
    }
@ -507,7 +637,7 @@ void report_realtime_status()
            ( BITFLAG_RT_STATUS_LIMIT_PINS| BITFLAG_RT_STATUS_PROBE_PIN | BITFLAG_RT_STATUS_CONTROL_PINS ))) {
        printPgmString(PSTR(",Pin:"));
        if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_LIMIT_PINS)) {
-        print_unsigned_int8(limits_get_state(),2,N_AXIS);
+          print_uint8_base2_ndigit(limits_get_state(),N_AXIS);
        }
        printPgmString(PSTR("|"));
        if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_PROBE_PIN)) {
@ -516,15 +646,200 @@ void report_realtime_status()
        }
        printPgmString(PSTR("|"));
        if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_CONTROL_PINS)) {
-        print_unsigned_int8(system_control_get_state(),2,N_CONTROL_PIN);
+          print_uint8_base2_ndigit(system_control_get_state(),N_CONTROL_PIN);
        }
      }
    #else
      if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_LIMIT_PINS)) {
        printPgmString(PSTR(",Lim:"));
-      print_unsigned_int8(limits_get_state(),2,N_AXIS);
+        print_uint8_base2_ndigit(limits_get_state(),N_AXIS);
      }
    #endif
    if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_OVERRIDES)) {
      printPgmString(PSTR(",Ov:"));
      print_uint8_base10(sys.f_override);
      serial_write(',');
      print_uint8_base10(sys.r_override);
      serial_write(',');
      print_uint8_base10(sys.spindle_speed_ovr);
      if (sys.toggle_ovr_mask) {
        printPgmString(PSTR("|T:"));
        if (sys.toggle_ovr_mask & TOGGLE_OVR_STOP_ACTIVE_MASK) { serial_write('S'); }
        if (sys.toggle_ovr_mask & TOGGLE_OVR_FLOOD_COOLANT) { serial_write('F'); }
        #ifdef ENABLE_M7
          if (sys.toggle_ovr_mask & TOGGLE_OVR_MIST_COOLANT) { serial_write('M'); }
        #endif
        bit_false(sys.toggle_ovr_mask, (TOGGLE_OVR_FLOOD_COOLANT|TOGGLE_OVR_FLOOD_COOLANT));
      }
    }
    printPgmString(PSTR(">\r\n"));
  #else
    uint8_t idx;
    int32_t current_position[N_AXIS]; // Copy current state of the system position variable
    memcpy(current_position,sys_position,sizeof(sys_position));
    float print_position[N_AXIS];
    system_convert_array_steps_to_mpos(print_position,current_position);
    // Report current machine state and sub-states
    serial_write('<');
    switch (sys.state) {
      case STATE_IDLE: printPgmString(PSTR("Idle")); break;
      case STATE_CYCLE: printPgmString(PSTR("Run")); break;
      case STATE_HOLD:
        if (!(sys.suspend & SUSPEND_JOG_CANCEL)) {
          printPgmString(PSTR("Hold:"));
          if (sys.suspend & SUSPEND_HOLD_COMPLETE) { serial_write('0'); } // Ready to resume
          else { serial_write('1'); } // Actively holding
          break;
        } // Continues to print jog state during jog cancel.
      case STATE_JOG: printPgmString(PSTR("Jog")); break;
      case STATE_HOMING: printPgmString(PSTR("Home")); break;
      case STATE_ALARM: printPgmString(PSTR("Alarm")); break;
      case STATE_CHECK_MODE: printPgmString(PSTR("Check")); break;
      case STATE_SAFETY_DOOR:
        printPgmString(PSTR("Door:"));
        if (sys.suspend & SUSPEND_INITIATE_RESTORE) {
          serial_write('3'); // Restoring
        } else {
          if (sys.suspend & SUSPEND_RETRACT_COMPLETE) {
            if (sys.suspend & SUSPEND_SAFETY_DOOR_AJAR) {
              serial_write('1'); // Door ajar
            } else {
              serial_write('0');
            } // Door closed and ready to resume
          } else {
            serial_write('2'); // Retracting
          }
        }
        break;
      case STATE_SLEEP: printPgmString(PSTR("Sleep")); break;
    }
    float wco[N_AXIS];
    if (bit_isfalse(settings.status_report_mask,BITFLAG_RT_STATUS_POSITION_TYPE) ||
        (sys.report_wco_counter >= REPORT_WCO_REFRESH_BUSY_COUNT) ) {
      for (idx=0; idx< N_AXIS; idx++) {
        // Apply work coordinate offsets and tool length offset to current position.
        wco[idx] = gc_state.coord_system[idx]+gc_state.coord_offset[idx];
        if (idx == TOOL_LENGTH_OFFSET_AXIS) { wco[idx] += gc_state.tool_length_offset; }
        if (bit_isfalse(settings.status_report_mask,BITFLAG_RT_STATUS_POSITION_TYPE)) {
          print_position[idx] -= wco[idx];
        }
      }
    }
    // Report machine position
    if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_POSITION_TYPE)) {
      printPgmString(PSTR("|MPos:"));
    } else {
      printPgmString(PSTR("|WPos:"));
    }
    report_util_axis_values(print_position);
    // Returns planner and serial read buffer states.
    #ifdef REPORT_FIELD_BUFFER_STATE
      if (bit_istrue(settings.status_report_mask,BITFLAG_RT_STATUS_BUFFER_STATE)) {
        printPgmString(PSTR("|Bf:"));
        print_uint8_base10(plan_get_block_buffer_available());
        serial_write(',');
        print_uint8_base10(serial_get_rx_buffer_available());
      }
    #endif
    #ifdef USE_LINE_NUMBERS
      #ifdef REPORT_FIELD_LINE_NUMBERS
        // Report current line number
        plan_block_t * cur_block = plan_get_current_block();
        if (cur_block != NULL) {
          uint32_t ln = cur_block->line_number;
          if (ln > 0) {
            printPgmString(PSTR("|Ln:"));
            printInteger(ln);
          }
        }
      #endif
    #endif
    // Report realtime rate
    #ifdef REPORT_FIELD_CURRENT_RATE
      printPgmString(PSTR("|F:"));
      printFloat_RateValue(st_get_realtime_rate());
    #endif
    #ifdef REPORT_FIELD_PIN_STATE
      uint8_t lim_pin_state = limits_get_state();
      uint8_t ctrl_pin_state = system_control_get_state();
      uint8_t prb_pin_state = probe_get_state();
      if (lim_pin_state | ctrl_pin_state | prb_pin_state) {
        printPgmString(PSTR("|Pn:"));
        if (prb_pin_state) { serial_write('P'); }
        if (lim_pin_state) {
          if (bit_istrue(lim_pin_state,bit(X_AXIS))) { serial_write('X'); }
          if (bit_istrue(lim_pin_state,bit(Y_AXIS))) { serial_write('Y'); }
          if (bit_istrue(lim_pin_state,bit(Z_AXIS))) { serial_write('Z'); }
        }
        if (ctrl_pin_state) {
          #ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
            if (bit_istrue(ctrl_pin_state,CONTROL_PIN_INDEX_SAFETY_DOOR)) { serial_write('D'); }
          #endif
          if (bit_istrue(ctrl_pin_state,CONTROL_PIN_INDEX_RESET)) { serial_write('R'); }
          if (bit_istrue(ctrl_pin_state,CONTROL_PIN_INDEX_FEED_HOLD)) { serial_write('H'); }
          if (bit_istrue(ctrl_pin_state,CONTROL_PIN_INDEX_CYCLE_START)) { serial_write('S'); }
        }
      }
    #endif
    #ifdef REPORT_FIELD_WORK_COORD_OFFSET
      if (sys.report_wco_counter++ >= REPORT_WCO_REFRESH_BUSY_COUNT) {
        if (sys.state & (STATE_HOMING | STATE_CYCLE | STATE_HOLD | STATE_JOG | STATE_SAFETY_DOOR)) {
          sys.report_wco_counter = 1; // Reset counter for slow refresh
        } else { sys.report_wco_counter = (REPORT_WCO_REFRESH_BUSY_COUNT-REPORT_WCO_REFRESH_IDLE_COUNT+1); }
        if (sys.report_ovr_counter >= REPORT_OVR_REFRESH_BUSY_COUNT) {
          sys.report_ovr_counter = (REPORT_OVR_REFRESH_BUSY_COUNT-1); // Set override on next report.
        }
        printPgmString(PSTR("|WCO:"));
        report_util_axis_values(wco);
      }
    #endif
    #ifdef REPORT_FIELD_OVERRIDES
      if (sys.report_ovr_counter++ >= REPORT_OVR_REFRESH_BUSY_COUNT) {
        if (sys.state & (STATE_HOMING | STATE_CYCLE | STATE_HOLD | STATE_JOG | STATE_SAFETY_DOOR)) {
          sys.report_ovr_counter = 1; // Reset counter for slow refresh
        } else { sys.report_ovr_counter = (REPORT_OVR_REFRESH_BUSY_COUNT-REPORT_OVR_REFRESH_IDLE_COUNT+1); }
        printPgmString(PSTR("|Ov:"));
        print_uint8_base10(sys.f_override);
        serial_write(',');
        print_uint8_base10(sys.r_override);
        serial_write(',');
        print_uint8_base10(sys.spindle_speed_ovr);
        if (sys.toggle_ovr_mask) {
          printPgmString(PSTR("|T:"));
          if (sys.toggle_ovr_mask & TOGGLE_OVR_STOP_ACTIVE_MASK) { serial_write('S'); }
          if (sys.toggle_ovr_mask & TOGGLE_OVR_FLOOD_COOLANT) { serial_write('F'); }
          #ifdef ENABLE_M7
            if (sys.toggle_ovr_mask & TOGGLE_OVR_MIST_COOLANT) { serial_write('M'); }
          #endif
          bit_false(sys.toggle_ovr_mask, (TOGGLE_OVR_FLOOD_COOLANT|TOGGLE_OVR_FLOOD_COOLANT));
        }
      }
    #endif
    serial_write('>');
    report_util_line_feed();
  #endif
 }
 #ifdef DEBUG
  void report_realtime_debug()
  {
  }
 #endif
--- a/grbl/report.h
+++ b/grbl/report.h
@ -2,7 +2,7 @@
  report.h - reporting and messaging methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -20,7 +20,7 @@
 #ifndef report_h
 #define report_h
-// Define Grbl status codes.
+// Define Grbl status codes. Valid values (0-255)
 #define STATUS_OK 0
 #define STATUS_EXPECTED_COMMAND_LETTER 1
 #define STATUS_BAD_NUMBER_FORMAT 2
@ -30,11 +30,14 @@
 #define STATUS_SETTING_STEP_PULSE_MIN 6
 #define STATUS_SETTING_READ_FAIL 7
 #define STATUS_IDLE_ERROR 8
-#define STATUS_ALARM_LOCK 9
+#define STATUS_SYSTEM_GC_LOCK 9
 #define STATUS_SOFT_LIMIT_ERROR 10
 #define STATUS_OVERFLOW 11
 #define STATUS_MAX_STEP_RATE_EXCEEDED 12
 #define STATUS_CHECK_DOOR 13
 #define STATUS_LINE_LENGTH_EXCEEDED 14
 #define STATUS_TRAVEL_EXCEEDED 15
 #define STATUS_INVALID_JOG_COMMAND 16
 #define STATUS_GCODE_UNSUPPORTED_COMMAND 20
 #define STATUS_GCODE_MODAL_GROUP_VIOLATION 21
@ -55,22 +58,29 @@
 #define STATUS_GCODE_UNUSED_WORDS 36
 #define STATUS_GCODE_G43_DYNAMIC_AXIS_ERROR 37
-// Define Grbl alarm codes.
+// Define Grbl alarm codes. Valid values (1-255). 0 is reserved.
-#define ALARM_HARD_LIMIT_ERROR 1
+#define ALARM_HARD_LIMIT_ERROR      EXEC_ALARM_HARD_LIMIT
-#define ALARM_SOFT_LIMIT_ERROR 2
+#define ALARM_SOFT_LIMIT_ERROR      EXEC_ALARM_SOFT_LIMIT
-#define ALARM_ABORT_CYCLE 3
+#define ALARM_ABORT_CYCLE           EXEC_ALARM_ABORT_CYCLE
-#define ALARM_PROBE_FAIL 4
+#define ALARM_PROBE_FAIL_INITIAL    EXEC_ALARM_PROBE_FAIL_INITIAL
-#define ALARM_HOMING_FAIL 5
+#define ALARM_PROBE_FAIL_CONTACT    EXEC_ALARM_PROBE_FAIL_CONTACT
 #define ALARM_HOMING_FAIL_RESET     EXEC_ALARM_HOMING_FAIL_RESET
 #define ALARM_HOMING_FAIL_DOOR      EXEC_ALARM_HOMING_FAIL_DOOR
 #define ALARM_HOMING_FAIL_PULLOFF   EXEC_ALARM_HOMING_FAIL_PULLOFF
 #define ALARM_HOMING_FAIL_APPROACH  EXEC_ALARM_HOMING_FAIL_APPROACH
-// Define Grbl feedback message codes.
+// Define Grbl feedback message codes. Valid values (0-255).
 #define MESSAGE_CRITICAL_EVENT 1
 #define MESSAGE_ALARM_LOCK 2
 #define MESSAGE_ALARM_UNLOCK 3
 #define MESSAGE_ENABLED 4
 #define MESSAGE_DISABLED 5
 #define MESSAGE_SAFETY_DOOR_AJAR 6
-#define MESSAGE_PROGRAM_END 7
+#define MESSAGE_CHECK_LIMITS 7
-#define MESSAGE_RESTORE_DEFAULTS 8
+#define MESSAGE_PROGRAM_END 8
 #define MESSAGE_RESTORE_DEFAULTS 9
 #define MESSAGE_SPINDLE_RESTORE 10
 #define MESSAGE_SLEEP_MODE 11
 // Prints system status messages.
 void report_status_message(uint8_t status_code);
@ -105,10 +115,15 @@ void report_ngc_parameters();
 // Prints current g-code parser mode state
 void report_gcode_modes();
-// Prints startup line
+// Prints startup line when requested and executed.
 void report_startup_line(uint8_t n, char *line);
 void report_execute_startup_message(char *line, uint8_t status_code);
 // Prints build info and user info
 void report_build_info(char *line);
 #ifdef DEBUG
  void report_realtime_debug();
 #endif
 #endif
--- a/grbl/serial.c
+++ b/grbl/serial.c
@ -2,7 +2,7 @@
  serial.c - Low level functions for sending and recieving bytes via the serial port
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -21,22 +21,29 @@
 #include "grbl.h"
 #define RX_RING_BUFFER (RX_BUFFER_SIZE+1)
 #define TX_RING_BUFFER (TX_BUFFER_SIZE+1)
-uint8_t serial_rx_buffer[RX_BUFFER_SIZE];
+uint8_t serial_rx_buffer[RX_RING_BUFFER];
 uint8_t serial_rx_buffer_head = 0;
 volatile uint8_t serial_rx_buffer_tail = 0;
-uint8_t serial_tx_buffer[TX_BUFFER_SIZE];
+uint8_t serial_tx_buffer[TX_RING_BUFFER];
 uint8_t serial_tx_buffer_head = 0;
 volatile uint8_t serial_tx_buffer_tail = 0;
-#ifdef ENABLE_XONXOFF
+// Returns the number of bytes available in the RX serial buffer.
-  volatile uint8_t flow_ctrl = XON_SENT; // Flow control state variable
+uint8_t serial_get_rx_buffer_available()
-#endif
+{
  uint8_t rtail = serial_rx_buffer_tail; // Copy to limit multiple calls to volatile
  if (serial_rx_buffer_head >= rtail) { return(RX_BUFFER_SIZE - (serial_rx_buffer_head-rtail)); }
  return((rtail-serial_rx_buffer_head-1));
 }
 // Returns the number of bytes used in the RX serial buffer.
 // NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
 uint8_t serial_get_rx_buffer_count()
 {
  uint8_t rtail = serial_rx_buffer_tail; // Copy to limit multiple calls to volatile
@ -51,7 +58,7 @@ uint8_t serial_get_tx_buffer_count()
 {
  uint8_t ttail = serial_tx_buffer_tail; // Copy to limit multiple calls to volatile
  if (serial_tx_buffer_head >= ttail) { return(serial_tx_buffer_head-ttail); }
-  return (TX_BUFFER_SIZE - (ttail-serial_tx_buffer_head));
+  return (TX_RING_BUFFER - (ttail-serial_tx_buffer_head));
 }
@ -68,23 +75,18 @@ void serial_init()
  UBRR0H = UBRR0_value >> 8;
  UBRR0L = UBRR0_value;
-  // enable rx and tx
+  // enable rx, tx, and interrupt on complete reception of a byte
-  UCSR0B |= 1<<RXEN0;
+  UCSR0B |= (1<<RXEN0 | 1<<TXEN0 | 1<<RXCIE0);
  UCSR0B |= 1<<TXEN0;
  // enable interrupt on complete reception of a byte
  UCSR0B |= 1<<RXCIE0;
  // defaults to 8-bit, no parity, 1 stop bit
 }
 // Writes one byte to the TX serial buffer. Called by main program.
 // TODO: Check if we can speed this up for writing strings, rather than single bytes.
 void serial_write(uint8_t data) {
  // Calculate next head
  uint8_t next_head = serial_tx_buffer_head + 1;
-  if (next_head == TX_BUFFER_SIZE) { next_head = 0; }
+  if (next_head == TX_RING_BUFFER) { next_head = 0; }
  // Wait until there is space in the buffer
  while (next_head == serial_tx_buffer_tail) {
@ -106,25 +108,14 @@ ISR(SERIAL_UDRE)
 {
  uint8_t tail = serial_tx_buffer_tail; // Temporary serial_tx_buffer_tail (to optimize for volatile)
  #ifdef ENABLE_XONXOFF
    if (flow_ctrl == SEND_XOFF) { 
      UDR0 = XOFF_CHAR; 
      flow_ctrl = XOFF_SENT; 
    } else if (flow_ctrl == SEND_XON) { 
      UDR0 = XON_CHAR; 
      flow_ctrl = XON_SENT; 
    } else
  #endif
  { 
  // Send a byte from the buffer
  UDR0 = serial_tx_buffer[tail];
  // Update tail position
  tail++;
-    if (tail == TX_BUFFER_SIZE) { tail = 0; }
+  if (tail == TX_RING_BUFFER) { tail = 0; }
  serial_tx_buffer_tail = tail;
  }
  // Turn off Data Register Empty Interrupt to stop tx-streaming if this concludes the transfer
  if (tail == serial_tx_buffer_head) { UCSR0B &= ~(1 << UDRIE0); }
@ -141,16 +132,9 @@ uint8_t serial_read()
    uint8_t data = serial_rx_buffer[tail];
    tail++;
-    if (tail == RX_BUFFER_SIZE) { tail = 0; }
+    if (tail == RX_RING_BUFFER) { tail = 0; }
    serial_rx_buffer_tail = tail;
    #ifdef ENABLE_XONXOFF
      if ((serial_get_rx_buffer_count() < RX_BUFFER_LOW) && flow_ctrl == XOFF_SENT) { 
        flow_ctrl = SEND_XON;
        UCSR0B |=  (1 << UDRIE0); // Force TX
      }
    #endif
    return data;
  }
 }
@ -162,31 +146,54 @@ ISR(SERIAL_RX)
  uint8_t next_head;
  // Pick off realtime command characters directly from the serial stream. These characters are
-  // not passed into the buffer, but these set system state flag bits for realtime execution.
+  // not passed into the main buffer, but these set system state flag bits for realtime execution.
  switch (data) {
    case CMD_RESET:         mc_reset(); break; // Call motion control reset routine.
    case CMD_STATUS_REPORT: system_set_exec_state_flag(EXEC_STATUS_REPORT); break; // Set as true
    case CMD_CYCLE_START:   system_set_exec_state_flag(EXEC_CYCLE_START); break; // Set as true
    case CMD_FEED_HOLD:     system_set_exec_state_flag(EXEC_FEED_HOLD); break; // Set as true
    default :
      if (data > 0x7F) { // Real-time control characters are extended ACSII only.
        switch(data) {
          case CMD_SAFETY_DOOR:   system_set_exec_state_flag(EXEC_SAFETY_DOOR); break; // Set as true
-    case CMD_RESET:         mc_reset(); break; // Call motion control reset routine.
+          case CMD_JOG_CANCEL:   
-    default: // Write character to buffer    
+            if (sys.state & STATE_JOG) { // Block all other states from invoking motion cancel.
              system_set_exec_state_flag(EXEC_MOTION_CANCEL); 
            }
            break; 
          #ifdef DEBUG
            case CMD_DEBUG_REPORT: {uint8_t sreg = SREG; cli(); bit_true(sys_rt_exec_debug,EXEC_DEBUG_REPORT); SREG = sreg;} break;
          #endif
          case CMD_FEED_OVR_RESET: system_set_exec_motion_override_flag(EXEC_FEED_OVR_RESET); break;
          case CMD_FEED_OVR_COARSE_PLUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_COARSE_PLUS); break;
          case CMD_FEED_OVR_COARSE_MINUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_COARSE_MINUS); break;
          case CMD_FEED_OVR_FINE_PLUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_FINE_PLUS); break;
          case CMD_FEED_OVR_FINE_MINUS: system_set_exec_motion_override_flag(EXEC_FEED_OVR_FINE_MINUS); break;
          case CMD_RAPID_OVR_RESET: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_RESET); break;
          case CMD_RAPID_OVR_MEDIUM: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_MEDIUM); break;
          case CMD_RAPID_OVR_LOW: system_set_exec_motion_override_flag(EXEC_RAPID_OVR_LOW); break;
          case CMD_SPINDLE_OVR_RESET: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_RESET); break;
          case CMD_SPINDLE_OVR_COARSE_PLUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_COARSE_PLUS); break;
          case CMD_SPINDLE_OVR_COARSE_MINUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_COARSE_MINUS); break;
          case CMD_SPINDLE_OVR_FINE_PLUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_FINE_PLUS); break;
          case CMD_SPINDLE_OVR_FINE_MINUS: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_FINE_MINUS); break;
          case CMD_SPINDLE_OVR_STOP: system_set_exec_accessory_override_flag(EXEC_SPINDLE_OVR_STOP); break;
          case CMD_COOLANT_FLOOD_OVR_TOGGLE: system_set_exec_accessory_override_flag(EXEC_COOLANT_FLOOD_OVR_TOGGLE); break;
          #ifdef ENABLE_M7
            case CMD_COOLANT_MIST_OVR_TOGGLE: system_set_exec_accessory_override_flag(EXEC_COOLANT_MIST_OVR_TOGGLE); break;
          #endif
        }
        // Throw away any unfound extended-ASCII character by not passing it to the serial buffer.
      } else { // Write character to buffer
        next_head = serial_rx_buffer_head + 1;
-      if (next_head == RX_BUFFER_SIZE) { next_head = 0; }
+        if (next_head == RX_RING_BUFFER) { next_head = 0; }
        // Write data to buffer unless it is full.
        if (next_head != serial_rx_buffer_tail) {
          serial_rx_buffer[serial_rx_buffer_head] = data;
          serial_rx_buffer_head = next_head;
        #ifdef ENABLE_XONXOFF
          if ((serial_get_rx_buffer_count() >= RX_BUFFER_FULL) && flow_ctrl == XON_SENT) {
            flow_ctrl = SEND_XOFF;
            UCSR0B |=  (1 << UDRIE0); // Force TX
        }
        #endif
      }
      //TODO: else alarm on overflow?
  }
 }
@ -194,8 +201,4 @@ ISR(SERIAL_RX)
 void serial_reset_read_buffer()
 {
  serial_rx_buffer_tail = serial_rx_buffer_head;
  #ifdef ENABLE_XONXOFF
    flow_ctrl = XON_SENT;
  #endif
 }
--- a/grbl/serial.h
+++ b/grbl/serial.h
@ -2,7 +2,7 @@
  serial.c - Low level functions for sending and recieving bytes via the serial port
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -27,21 +27,15 @@
  #define RX_BUFFER_SIZE 128
 #endif
 #ifndef TX_BUFFER_SIZE
-  #define TX_BUFFER_SIZE 64
+  #ifdef USE_LINE_NUMBERS
    #define TX_BUFFER_SIZE 100
  #else
    #define TX_BUFFER_SIZE 90
  #endif
 #endif
 #define SERIAL_NO_DATA 0xff
 #ifdef ENABLE_XONXOFF
  #define RX_BUFFER_FULL 96 // XOFF high watermark
  #define RX_BUFFER_LOW 64 // XON low watermark
  #define SEND_XOFF 1
  #define SEND_XON 2
  #define XOFF_SENT 3
  #define XON_SENT 4
  #define XOFF_CHAR 0x13
  #define XON_CHAR 0x11
 #endif
 void serial_init();
@ -54,7 +48,11 @@ uint8_t serial_read();
 // Reset and empty data in read buffer. Used by e-stop and reset.
 void serial_reset_read_buffer();
 // Returns the number of bytes available in the RX serial buffer.
 uint8_t serial_get_rx_buffer_available();
 // Returns the number of bytes used in the RX serial buffer.
 // NOTE: Deprecated. Not used unless classic status reports are enabled in config.h.
 uint8_t serial_get_rx_buffer_count();
 // Returns the number of bytes used in the TX serial buffer.
--- a/grbl/settings.c
+++ b/grbl/settings.c
@ -2,7 +2,7 @@
  settings.c - eeprom configuration handling
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon  
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -27,14 +27,19 @@ settings_t settings;
 // Method to store startup lines into EEPROM
 void settings_store_startup_line(uint8_t n, char *line)
 {
  #ifdef FORCE_BUFFER_SYNC_DURING_EEPROM_WRITE
    protocol_buffer_synchronize(); // A startup line may contain a motion and be executing. 
  #endif
  uint32_t addr = n*(LINE_BUFFER_SIZE+1)+EEPROM_ADDR_STARTUP_BLOCK;
  memcpy_to_eeprom_with_checksum(addr,(char*)line, LINE_BUFFER_SIZE);
 }
 // Method to store build info into EEPROM
 // NOTE: This function can only be called in IDLE state.
 void settings_store_build_info(char *line)
 {
  // Build info can only be stored when state is IDLE.
  memcpy_to_eeprom_with_checksum(EEPROM_ADDR_BUILD_INFO,(char*)line, LINE_BUFFER_SIZE);
 }
@ -42,12 +47,16 @@ void settings_store_build_info(char *line)
 // Method to store coord data parameters into EEPROM
 void settings_write_coord_data(uint8_t coord_select, float *coord_data)
 {
  #ifdef FORCE_BUFFER_SYNC_DURING_EEPROM_WRITE
    protocol_buffer_synchronize();
  #endif
  uint32_t addr = coord_select*(sizeof(float)*N_AXIS+1) + EEPROM_ADDR_PARAMETERS;
  memcpy_to_eeprom_with_checksum(addr,(char*)coord_data, sizeof(float)*N_AXIS);
 }
 // Method to store Grbl global settings struct and version number into EEPROM
 // NOTE: This function can only be called in IDLE state.
 void write_global_settings()
 {
  eeprom_put_char(0, SETTINGS_VERSION);
@ -77,11 +86,13 @@ void settings_restore(uint8_t restore_flag) {
    settings.flags = 0;
    if (DEFAULT_REPORT_INCHES) { settings.flags |= BITFLAG_REPORT_INCHES; }
    if (DEFAULT_LASER_MODE) { settings.flags |= BITFLAG_LASER_MODE; }
    if (DEFAULT_INVERT_ST_ENABLE) { settings.flags |= BITFLAG_INVERT_ST_ENABLE; }
 	if (DEFAULT_INVERT_LIMIT_PINS) { settings.flags |= BITFLAG_INVERT_LIMIT_PINS; }
 	if (DEFAULT_SOFT_LIMIT_ENABLE) { settings.flags |= BITFLAG_SOFT_LIMIT_ENABLE; }
    if (DEFAULT_HARD_LIMIT_ENABLE) { settings.flags |= BITFLAG_HARD_LIMIT_ENABLE; }
    if (DEFAULT_HOMING_ENABLE) { settings.flags |= BITFLAG_HOMING_ENABLE; }
    if (DEFAULT_SOFT_LIMIT_ENABLE) { settings.flags |= BITFLAG_SOFT_LIMIT_ENABLE; }
    if (DEFAULT_INVERT_LIMIT_PINS) { settings.flags |= BITFLAG_INVERT_LIMIT_PINS; }
    if (DEFAULT_INVERT_PROBE_PIN) { settings.flags |= BITFLAG_INVERT_PROBE_PIN; }
    settings.steps_per_mm[X_AXIS] = DEFAULT_X_STEPS_PER_MM;
    settings.steps_per_mm[Y_AXIS] = DEFAULT_Y_STEPS_PER_MM;
@ -109,13 +120,18 @@ void settings_restore(uint8_t restore_flag) {
  if (restore_flag & SETTINGS_RESTORE_STARTUP_LINES) {
    #if N_STARTUP_LINE > 0
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK, 0);
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+1, 0); // Checksum
    #endif
    #if N_STARTUP_LINE > 1
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+(LINE_BUFFER_SIZE+1), 0);
      eeprom_put_char(EEPROM_ADDR_STARTUP_BLOCK+(LINE_BUFFER_SIZE+2), 0); // Checksum
    #endif
  }
-  if (restore_flag & SETTINGS_RESTORE_BUILD_INFO) { eeprom_put_char(EEPROM_ADDR_BUILD_INFO , 0); }
+  if (restore_flag & SETTINGS_RESTORE_BUILD_INFO) {
    eeprom_put_char(EEPROM_ADDR_BUILD_INFO , 0);
    eeprom_put_char(EEPROM_ADDR_BUILD_INFO+1 , 0); // Checksum
  }
 }
@ -238,6 +254,7 @@ uint8_t settings_store_global_setting(uint8_t parameter, float value) {
      case 6: // Reset to ensure change. Immediate re-init may cause problems.
        if (int_value) { settings.flags |= BITFLAG_INVERT_PROBE_PIN; }
        else { settings.flags &= ~BITFLAG_INVERT_PROBE_PIN; }
        probe_configure_invert_mask(false);
        break;
      case 10: settings.status_report_mask = int_value; break;
      case 11: settings.junction_deviation = value; break;
@ -269,8 +286,16 @@ uint8_t settings_store_global_setting(uint8_t parameter, float value) {
      case 25: settings.homing_seek_rate = value; break;
      case 26: settings.homing_debounce_delay = int_value; break;
      case 27: settings.homing_pulloff = value; break;
-      case 30: settings.rpm_max = value; break;
+      case 30: settings.rpm_max = value; spindle_init(); break; // Re-initialize spindle rpm calibration
-      case 31: settings.rpm_min = value; break;
+      case 31: settings.rpm_min = value; spindle_init(); break; // Re-initialize spindle rpm calibration
      case 32:
        #ifdef VARIABLE_SPINDLE
          if (int_value) { settings.flags |= BITFLAG_LASER_MODE; }
          else { settings.flags &= ~BITFLAG_LASER_MODE; }
        #else
          return(STATUS_SETTING_DISABLED);
        #endif
        break;
      default:
        return(STATUS_INVALID_STATEMENT);
    }
@ -287,18 +312,6 @@ void settings_init() {
    settings_restore(SETTINGS_RESTORE_ALL); // Force restore all EEPROM data.
    report_grbl_settings();
  }
  // NOTE: Checking paramater data, startup lines, and build info string should be done here, 
  // but it seems fairly redundant. Each of these can be manually checked and reset or restored.
  // Check all parameter data into a dummy variable. If error, reset to zero, otherwise do nothing.
  // float coord_data[N_AXIS];
  // uint8_t i;
  // for (i=0; i<=SETTING_INDEX_NCOORD; i++) {
  //   if (!settings_read_coord_data(i, coord_data)) {
  // 	report_status_message(STATUS_SETTING_READ_FAIL);
  //   }
  // }
  // NOTE: Startup lines are checked and executed by protocol_main_loop at the end of initialization.
 }
--- a/grbl/settings.h
+++ b/grbl/settings.h
@ -2,7 +2,7 @@
  settings.h - eeprom configuration handling
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -31,7 +31,7 @@
 // Define bit flag masks for the boolean settings in settings.flag.
 #define BITFLAG_REPORT_INCHES      bit(0)
-// #define BITFLAG_AUTO_START         bit(1) // Obsolete. Don't alter to keep back compatibility.
+#define BITFLAG_LASER_MODE         bit(1)
 #define BITFLAG_INVERT_ST_ENABLE   bit(2)
 #define BITFLAG_HARD_LIMIT_ENABLE  bit(3)
 #define BITFLAG_HOMING_ENABLE      bit(4)
@ -40,20 +40,28 @@
 #define BITFLAG_INVERT_PROBE_PIN   bit(7)
 // Define status reporting boolean enable bit flags in settings.status_report_mask
-#define BITFLAG_RT_STATUS_MACHINE_POSITION  bit(0)
+#ifdef USE_CLASSIC_REALTIME_REPORT
-#define BITFLAG_RT_STATUS_WORK_POSITION     bit(1)
+  #define BITFLAG_RT_STATUS_MACHINE_POSITION  bit(0)
-#define BITFLAG_RT_STATUS_PLANNER_BUFFER    bit(2)
+  #define BITFLAG_RT_STATUS_WORK_POSITION     bit(1)
-#define BITFLAG_RT_STATUS_SERIAL_RX         bit(3)
+  #define BITFLAG_RT_STATUS_PLANNER_BUFFER    bit(2)
-#define BITFLAG_RT_STATUS_LIMIT_PINS        bit(4)
+  #define BITFLAG_RT_STATUS_SERIAL_RX         bit(3)
-#define BITFLAG_RT_STATUS_PROBE_PIN         bit(5)
+  #define BITFLAG_RT_STATUS_LIMIT_PINS        bit(4)
-#define BITFLAG_RT_STATUS_CONTROL_PINS      bit(6)
+  #define BITFLAG_RT_STATUS_PROBE_PIN         bit(5)
  #define BITFLAG_RT_STATUS_CONTROL_PINS      bit(6)
  #define BITFLAG_RT_STATUS_OVERRIDES         bit(7)
 #else
  #define BITFLAG_RT_STATUS_POSITION_TYPE     bit(0)
  #define BITFLAG_RT_STATUS_BUFFER_STATE      bit(1)
 #endif
 // Define settings restore bitflags.
 #define SETTINGS_RESTORE_ALL 0xFF // All bitflags
 #define SETTINGS_RESTORE_DEFAULTS bit(0)
 #define SETTINGS_RESTORE_PARAMETERS bit(1)
 #define SETTINGS_RESTORE_STARTUP_LINES bit(2)
 #define SETTINGS_RESTORE_BUILD_INFO bit(3)
 #ifndef SETTINGS_RESTORE_ALL
  #define SETTINGS_RESTORE_ALL 0xFF // All bitflags
 #endif
 // Define EEPROM memory address location values for Grbl settings and parameters
 // NOTE: The Atmega328p has 1KB EEPROM. The upper half is reserved for parameters and
--- a/grbl/spindle_control.c
+++ b/grbl/spindle_control.c
@ -2,7 +2,7 @@
  spindle_control.c - spindle control methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -22,6 +22,18 @@
 #include "grbl.h"
 #ifdef SPINDLE_MINIMUM_PWM
  #define SPINDLE_PWM_MIN_VALUE SPINDLE_MINIMUM_PWM
 #else
  #define SPINDLE_PWM_MIN_VALUE 0.0
 #endif
 #define SPINDLE_PWM_RANGE (SPINDLE_PWM_MAX_VALUE-SPINDLE_PWM_MIN_VALUE)
 #ifdef VARIABLE_SPINDLE
  static float pwm_gradient; // Precalulated value to speed up rpm to PWM conversions.
 #endif
 void spindle_init()
 {
  #ifdef VARIABLE_SPINDLE
@ -37,6 +49,8 @@ void spindle_init()
      SPINDLE_DIRECTION_DDR |= (1<<SPINDLE_DIRECTION_BIT); // Configure as output pin.
    #endif
    pwm_gradient = SPINDLE_PWM_RANGE/(settings.rpm_max-settings.rpm_min);
  #else
    // Configure no variable spindle and only enable pin.
@ -49,12 +63,14 @@ void spindle_init()
 }
 // Stop and start spindle routines. Called by all spindle routines and various interrupts. 
 // Keep routine small, fast, and efficient.
 void spindle_stop()
 {
  // On the Uno, spindle enable and PWM are shared. Other CPUs have seperate enable pin.
  #ifdef VARIABLE_SPINDLE
    SPINDLE_TCCRA_REGISTER &= ~(1<<SPINDLE_COMB_BIT); // Disable PWM. Output voltage is zero.
-    #if defined(CPU_MAP_ATMEGA2560) || defined(USE_SPINDLE_DIR_AS_ENABLE_PIN)
+    #ifdef USE_SPINDLE_DIR_AS_ENABLE_PIN
      #ifdef INVERT_SPINDLE_ENABLE_PIN
        SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);  // Set pin to high
      #else
@ -71,7 +87,47 @@ void spindle_stop()
 }
-void spindle_set_state(uint8_t state, float rpm)
+#ifdef VARIABLE_SPINDLE
  // Called by spindle state functions and stepper ISR. Keep routine small, fast, and efficient.
  void spindle_set_speed(uint8_t pwm_value)
  {
    if (pwm_value == SPINDLE_PWM_OFF_VALUE) {
      spindle_stop();
    } else {
      SPINDLE_OCR_REGISTER = pwm_value; // Set PWM output level.
      SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
      #if defined(USE_SPINDLE_DIR_AS_ENABLE_PIN)
        #ifdef INVERT_SPINDLE_ENABLE_PIN
          SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
        #else
          SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
        #endif
      #endif
    }
  }
  // Called by spindle state functions and step segment generator.
  uint8_t spindle_compute_pwm_value(float rpm) // 328p PWM register is 8-bit.
  {
    // Calculate PWM register value based on rpm max/min settings and programmed rpm.
    if ((settings.rpm_min >= settings.rpm_max) || (rpm >= settings.rpm_max)) {
      // No PWM range possible. Set simple on/off spindle control pin state.
      return(SPINDLE_PWM_MAX_VALUE);
    } else if (rpm < settings.rpm_min) {
      if (rpm == 0.0) { return(SPINDLE_PWM_OFF_VALUE); }
      else { return(SPINDLE_PWM_MIN_VALUE); }
    } else {
      return(floor( (rpm-settings.rpm_min)*pwm_gradient + (SPINDLE_PWM_MIN_VALUE+0.5)));
    }
  }
 #endif
 // Immediately sets spindle running state with direction and spindle rpm via PWM, if enabled.
 // Called by spindle_run() after sync and parking motion/spindle stop override during restore.
 void spindle_set_state(uint8_t state, uint8_t pwm_value)
 {
  if (sys.abort) { return; } // Block during abort.
@ -92,39 +148,7 @@ void spindle_set_state(uint8_t state, float rpm)
    #ifdef VARIABLE_SPINDLE
-      // TODO: Install the optional capability for frequency-based output for servos.
+      spindle_set_speed(pwm_value);
      uint8_t current_pwm;  // 328p PWM register is 8-bit.
      // Calculate PWM register value based on rpm max/min settings and programmed rpm.
      if (rpm <= 0.0) { spindle_stop(); } // RPM should never be negative, but check anyway.
      else {
        if (settings.rpm_max <= settings.rpm_min) {
          // No PWM range possible. Set simple on/off spindle control pin state.
          current_pwm = SPINDLE_PWM_MAX_VALUE;
        } else {
          if (rpm > settings.rpm_max) { rpm = settings.rpm_max; }
          if (rpm < settings.rpm_min) { rpm = settings.rpm_min; }
          #ifdef SPINDLE_MINIMUM_PWM
            float pwm_gradient = (SPINDLE_PWM_MAX_VALUE-SPINDLE_MINIMUM_PWM)/(settings.rpm_max-settings.rpm_min);
            current_pwm = floor( (rpm-settings.rpm_min)*pwm_gradient + (SPINDLE_MINIMUM_PWM+0.5));
          #else
            float pwm_gradient = (SPINDLE_PWM_MAX_VALUE)/(settings.rpm_max-settings.rpm_min);
            current_pwm = floor( (rpm-settings.rpm_min)*pwm_gradient + 0.5);
          #endif
        }
        SPINDLE_OCR_REGISTER = current_pwm; // Set PWM output level.
        SPINDLE_TCCRA_REGISTER |= (1<<SPINDLE_COMB_BIT); // Ensure PWM output is enabled.
        // On the Uno, spindle enable and PWM are shared, unless otherwise specified.
        #if defined(USE_SPINDLE_DIR_AS_ENABLE_PIN) 
          #ifdef INVERT_SPINDLE_ENABLE_PIN
            SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);
          #else
            SPINDLE_ENABLE_PORT |= (1<<SPINDLE_ENABLE_BIT);
          #endif
        #endif
      }
    #else
@ -142,9 +166,14 @@ void spindle_set_state(uint8_t state, float rpm)
 }
 // Called by g-code parser when setting spindle state and requires a buffer sync.
 void spindle_run(uint8_t state, float rpm)
 {
  if (sys.state == STATE_CHECK_MODE) { return; }
  protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
-  spindle_set_state(state, rpm);
+  #ifdef VARIABLE_SPINDLE
    spindle_set_state(state, spindle_compute_pwm_value(rpm));
  #else
    spindle_set_state(state,0); // Send null pwm value. Not used.
  #endif
 }
--- a/grbl/spindle_control.h
+++ b/grbl/spindle_control.h
@ -2,7 +2,7 @@
  spindle_control.h - spindle control methods
  Part of Grbl
-  Copyright (c) 2012-2015 Sungeun K. Jeon
+  Copyright (c) 2012-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -26,12 +26,18 @@
 // Initializes spindle pins and hardware PWM, if enabled.
 void spindle_init();
-// Sets spindle direction and spindle rpm via PWM, if enabled.
+// Called by g-code parser when setting spindle state and requires a buffer sync.
 void spindle_run(uint8_t direction, float rpm);
-void spindle_set_state(uint8_t state, float rpm);
+// Immediately sets spindle running state with direction and spindle rpm via PWM, if enabled.
 // Called by spindle_run() after sync and parking motion/spindle stop override during restore.
 void spindle_set_state(uint8_t state, uint8_t pwm_value);
-// Kills spindle.
+// Stop and start spindle routines. Called by all spindle routines and stepper ISR.
 void spindle_stop();
 void spindle_set_speed(uint8_t pwm_value); // Variable spindle only.
 uint8_t spindle_compute_pwm_value(float rpm); // 328p PWM register is 8-bit. Variable spindle only.
 #endif
--- a/grbl/stepper.c
+++ b/grbl/stepper.c
@ -2,7 +2,7 @@
  stepper.c - stepper motor driver: executes motion plans using stepper motors
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -28,10 +28,12 @@
 #define RAMP_ACCEL 0
 #define RAMP_CRUISE 1
 #define RAMP_DECEL 2
 #define RAMP_DECEL_OVERRIDE 3
 #define PREP_FLAG_RECALCULATE bit(0)
 #define PREP_FLAG_HOLD_PARTIAL_BLOCK bit(1)
 #define PREP_FLAG_PARKING bit(2)
 #define PREP_FLAG_DECEL_OVERRIDE bit(3)
 // Define Adaptive Multi-Axis Step-Smoothing(AMASS) levels and cutoff frequencies. The highest level
 // frequency bin starts at 0Hz and ends at its cutoff frequency. The next lower level frequency bin
@ -57,6 +59,9 @@
 // data for its own use.
 typedef struct {
  uint8_t direction_bits;
  #ifdef VARIABLE_SPINDLE
    uint8_t spindle_pwm;
  #endif
  uint32_t steps[N_AXIS];
  uint32_t step_event_count;
 } st_block_t;
@ -197,9 +202,7 @@ void st_wake_up()
  if (bit_istrue(settings.flags,BITFLAG_INVERT_ST_ENABLE)) { STEPPERS_DISABLE_PORT |= (1<<STEPPERS_DISABLE_BIT); }
  else { STEPPERS_DISABLE_PORT &= ~(1<<STEPPERS_DISABLE_BIT); }
-//   if (sys.state & (STATE_CYCLE | STATE_HOMING)){
+  // Initialize stepper output bits to ensure first ISR call does not step.
    // Initialize stepper output bits
    st.dir_outbits = dir_port_invert_mask; 
  st.step_outbits = step_port_invert_mask;
  // Initialize step pulse timing from settings. Here to ensure updating after re-writing.
@ -215,7 +218,6 @@ void st_wake_up()
  // Enable Stepper Driver Interrupt
  TIMSK1 |= (1<<OCIE1A);
 //   }
 }
@ -229,7 +231,7 @@ void st_go_idle()
  // Set stepper driver idle state, disabled or enabled, depending on settings and circumstances.
  bool pin_state = false; // Keep enabled.
-  if (((settings.stepper_idle_lock_time != 0xff) || sys_rt_exec_alarm) && sys.state != STATE_HOMING) {
+  if (((settings.stepper_idle_lock_time != 0xff) || sys_rt_exec_alarm || sys.state == STATE_SLEEP) && sys.state != STATE_HOMING) {
    // Force stepper dwell to lock axes for a defined amount of time to ensure the axes come to a complete
    // stop and not drift from residual inertial forces at the end of the last movement.
    delay_ms(settings.stepper_idle_lock_time);
@ -291,7 +293,6 @@ void st_go_idle()
 // with probing and homing cycles that require true real-time positions.
 ISR(TIMER1_COMPA_vect)
 {
 // SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
  if (busy) { return; } // The busy-flag is used to avoid reentering this interrupt
  // Set the direction pins a couple of nanoseconds before we step the steppers
@ -346,6 +347,11 @@ ISR(TIMER1_COMPA_vect)
        st.steps[Z_AXIS] = st.exec_block->steps[Z_AXIS] >> st.exec_segment->amass_level;
      #endif
      #ifdef VARIABLE_SPINDLE
        // Set real-time spindle output as segment is loaded, just prior to the first step.
        spindle_set_speed(st.exec_block->spindle_pwm);
      #endif
    } else {
      // Segment buffer empty. Shutdown.
      st_go_idle();
@ -356,7 +362,7 @@ ISR(TIMER1_COMPA_vect)
  // Check probing state.
-  probe_state_monitor();
+  if (sys_probe_state == PROBE_ACTIVE) { probe_state_monitor(); }
  // Reset step out bits.
  st.step_outbits = 0;
@ -370,8 +376,8 @@ ISR(TIMER1_COMPA_vect)
  if (st.counter_x > st.exec_block->step_event_count) {
    st.step_outbits |= (1<<X_STEP_BIT);
    st.counter_x -= st.exec_block->step_event_count;
-    if (st.exec_block->direction_bits & (1<<X_DIRECTION_BIT)) { sys.position[X_AXIS]--; }
+    if (st.exec_block->direction_bits & (1<<X_DIRECTION_BIT)) { sys_position[X_AXIS]--; }
-    else { sys.position[X_AXIS]++; }
+    else { sys_position[X_AXIS]++; }
  }
  #ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
    st.counter_y += st.steps[Y_AXIS];
@ -381,8 +387,8 @@ ISR(TIMER1_COMPA_vect)
  if (st.counter_y > st.exec_block->step_event_count) {
    st.step_outbits |= (1<<Y_STEP_BIT);
    st.counter_y -= st.exec_block->step_event_count;
-    if (st.exec_block->direction_bits & (1<<Y_DIRECTION_BIT)) { sys.position[Y_AXIS]--; }
+    if (st.exec_block->direction_bits & (1<<Y_DIRECTION_BIT)) { sys_position[Y_AXIS]--; }
-    else { sys.position[Y_AXIS]++; }
+    else { sys_position[Y_AXIS]++; }
  }
  #ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING
    st.counter_z += st.steps[Z_AXIS];
@ -392,8 +398,8 @@ ISR(TIMER1_COMPA_vect)
  if (st.counter_z > st.exec_block->step_event_count) {
    st.step_outbits |= (1<<Z_STEP_BIT);
    st.counter_z -= st.exec_block->step_event_count;
-    if (st.exec_block->direction_bits & (1<<Z_DIRECTION_BIT)) { sys.position[Z_AXIS]--; }
+    if (st.exec_block->direction_bits & (1<<Z_DIRECTION_BIT)) { sys_position[Z_AXIS]--; }
-    else { sys.position[Z_AXIS]++; }
+    else { sys_position[Z_AXIS]++; }
  }
  // During a homing cycle, lock out and prevent desired axes from moving.
@ -408,7 +414,6 @@ ISR(TIMER1_COMPA_vect)
  st.step_outbits ^= step_port_invert_mask;  // Apply step port invert mask
  busy = false;
 // SPINDLE_ENABLE_PORT ^= 1<<SPINDLE_ENABLE_BIT; // Debug: Used to time ISR
 }
@ -472,6 +477,7 @@ void st_reset()
  busy = false;
  st_generate_step_dir_invert_masks();
  st.dir_outbits = dir_port_invert_mask; // Initialize direction bits to default.
  // Initialize step and direction port pins.
  STEP_PORT = (STEP_PORT & ~STEP_MASK) | step_port_invert_mask;
@ -545,7 +551,6 @@ static uint8_t st_next_block_index(uint8_t block_index)
  // Restores the step segment buffer to the normal run state after a parking motion.
  // NOTE: This function does not compile if parking is disabled.
  void st_parking_restore_buffer()
  {
    // Restore step execution data and flags of partially completed block, if necessary.
@ -588,36 +593,23 @@ void st_prep_buffer()
    // Determine if we need to load a new planner block or if the block needs to be recomputed.
    if (pl_block == NULL) {
      #ifdef PARKING_ENABLE
      // Query planner for a queued block
-        if (sys.step_control & STEP_CONTROL_EXECUTE_PARK) { pl_block = plan_get_parking_block(); }
+      if (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION) { pl_block = plan_get_system_motion_block(); }
      else { pl_block = plan_get_current_block(); }
      if (pl_block == NULL) { return; } // No planner blocks. Exit.
      // Check if we need to only recompute the velocity profile or load a new block.
      if (prep.recalculate_flag & PREP_FLAG_RECALCULATE) {
        #ifdef PARKING_ENABLE
          if (prep.recalculate_flag & PREP_FLAG_PARKING) { prep.recalculate_flag &= ~(PREP_FLAG_RECALCULATE); }
          else { prep.recalculate_flag = false; }
        } else {
        #else
        // Query planner for a queued block
        pl_block = plan_get_current_block();
        if (pl_block == NULL) { return; } // No planner blocks. Exit.
        // Check if we need to only recompute the velocity profile or load a new block.
        if (prep.recalculate_flag & PREP_FLAG_RECALCULATE) {
          prep.recalculate_flag = false;
        #endif
      } else {
      #endif
        // Load the Bresenham stepping data for the block.
        prep.st_block_index = st_next_block_index(prep.st_block_index);
@ -644,10 +636,11 @@ void st_prep_buffer()
        prep.req_mm_increment = REQ_MM_INCREMENT_SCALAR/prep.step_per_mm;
        prep.dt_remainder = 0.0; // Reset for new segment block
-        if (sys.step_control & STEP_CONTROL_EXECUTE_HOLD) {
+        if ((sys.step_control & STEP_CONTROL_EXECUTE_HOLD) || (prep.recalculate_flag & PREP_FLAG_DECEL_OVERRIDE)) {
          // New block loaded mid-hold. Override planner block entry speed to enforce deceleration.
          prep.current_speed = prep.exit_speed;
          pl_block->entry_speed_sqr = prep.exit_speed*prep.exit_speed;
          prep.recalculate_flag &= ~(PREP_FLAG_DECEL_OVERRIDE);
        } else {
          prep.current_speed = sqrt(pl_block->entry_speed_sqr);
        }
@ -679,28 +672,53 @@ void st_prep_buffer()
 				prep.ramp_type = RAMP_ACCEL; // Initialize as acceleration ramp.
 				prep.accelerate_until = pl_block->millimeters;
-				#ifdef PARKING_ENABLE
+				float exit_speed_sqr;
-					if (sys.step_control & STEP_CONTROL_EXECUTE_PARK) { prep.exit_speed = 0.0; }
+				float nominal_speed;
-					else { prep.exit_speed = plan_get_exec_block_exit_speed(); }
+        if (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION) {
-				#else
+          prep.exit_speed = exit_speed_sqr = 0.0; // Enforce stop at end of system motion.
-					prep.exit_speed = plan_get_exec_block_exit_speed();
+        } else {
-				#endif
+          exit_speed_sqr = plan_get_exec_block_exit_speed_sqr();
          prep.exit_speed = sqrt(exit_speed_sqr);
        }
-				float exit_speed_sqr = prep.exit_speed*prep.exit_speed;
+        nominal_speed = plan_compute_profile_nominal_speed(pl_block);
 				float nominal_speed_sqr = nominal_speed*nominal_speed;
 				float intersect_distance =
 								0.5*(pl_block->millimeters+inv_2_accel*(pl_block->entry_speed_sqr-exit_speed_sqr));
-				if (intersect_distance > 0.0) {
+
        if (pl_block->entry_speed_sqr > nominal_speed_sqr) { // Only occurs during override reductions.
          prep.accelerate_until = pl_block->millimeters - inv_2_accel*(pl_block->entry_speed_sqr-nominal_speed_sqr);
          if (prep.accelerate_until <= 0.0) { // Deceleration-only.
            prep.ramp_type = RAMP_DECEL;
            // prep.decelerate_after = pl_block->millimeters;
            // prep.maximum_speed = prep.current_speed;
            // Compute override block exit speed since it doesn't match the planner exit speed.
            prep.exit_speed = sqrt(pl_block->entry_speed_sqr - 2*pl_block->acceleration*pl_block->millimeters);
            prep.recalculate_flag |= PREP_FLAG_DECEL_OVERRIDE; // Flag to load next block as deceleration override.
            // TODO: Determine correct handling of parameters in deceleration-only.
            // Can be tricky since entry speed will be current speed, as in feed holds.
            // Also, look into near-zero speed handling issues with this.
          } else {
            // Decelerate to cruise or cruise-decelerate types. Guaranteed to intersect updated plan.
            prep.decelerate_after = inv_2_accel*(nominal_speed_sqr-exit_speed_sqr);
            prep.maximum_speed = nominal_speed;
            prep.ramp_type = RAMP_DECEL_OVERRIDE;
          }
 				} else if (intersect_distance > 0.0) {
 					if (intersect_distance < pl_block->millimeters) { // Either trapezoid or triangle types
 						// NOTE: For acceleration-cruise and cruise-only types, following calculation will be 0.0.
-						prep.decelerate_after = inv_2_accel*(pl_block->nominal_speed_sqr-exit_speed_sqr);
+						prep.decelerate_after = inv_2_accel*(nominal_speed_sqr-exit_speed_sqr);
 						if (prep.decelerate_after < intersect_distance) { // Trapezoid type
-							prep.maximum_speed = sqrt(pl_block->nominal_speed_sqr);
+							prep.maximum_speed = nominal_speed;
-							if (pl_block->entry_speed_sqr == pl_block->nominal_speed_sqr) { 
+							if (pl_block->entry_speed_sqr == nominal_speed_sqr) {
 								// Cruise-deceleration or cruise-only type.
 								prep.ramp_type = RAMP_CRUISE;
 							} else {
 								// Full-trapezoid or acceleration-cruise types
-								prep.accelerate_until -= inv_2_accel*(pl_block->nominal_speed_sqr-pl_block->entry_speed_sqr); 
+								prep.accelerate_until -= inv_2_accel*(nominal_speed_sqr-pl_block->entry_speed_sqr);
 							}
 						} else { // Triangle type
 							prep.accelerate_until = intersect_distance;
@ -718,8 +736,22 @@ void st_prep_buffer()
 					prep.maximum_speed = prep.exit_speed;
 				}
 			}
      #ifdef VARIABLE_SPINDLE  
        bit_true(sys.step_control, STEP_CONTROL_UPDATE_SPINDLE_PWM); // Force update whenever updating block.
      #endif
    }
    #ifdef VARIABLE_SPINDLE
      if (sys.step_control & STEP_CONTROL_UPDATE_SPINDLE_PWM) {    
 			  // Configure correct spindle PWM state for block. Updates with planner changes and spindle speed overrides.
 			  if (pl_block->condition & (PL_COND_FLAG_SPINDLE_CW | PL_COND_FLAG_SPINDLE_CCW)) {
          st_prep_block->spindle_pwm = spindle_compute_pwm_value((0.01*sys.spindle_speed_ovr)*pl_block->spindle_speed);
        } else { st_prep_block->spindle_pwm = SPINDLE_PWM_OFF_VALUE; }
        bit_false(sys.step_control,STEP_CONTROL_UPDATE_SPINDLE_PWM);
      }
    #endif
    // Initialize new segment
    segment_t *prep_segment = &segment_buffer[segment_buffer_head];
@ -751,6 +783,20 @@ void st_prep_buffer()
    do {
      switch (prep.ramp_type) {
        case RAMP_DECEL_OVERRIDE:
          speed_var = pl_block->acceleration*time_var;
          mm_var = time_var*(prep.current_speed - 0.5*speed_var);
          mm_remaining -= mm_var;
          if ((mm_remaining < prep.accelerate_until) || (mm_var <= 0)) {
            // Cruise or cruise-deceleration types only for deceleration override.
            mm_remaining = prep.accelerate_until; // NOTE: 0.0 at EOB
            time_var = 2.0*(pl_block->millimeters-mm_remaining)/(prep.current_speed+prep.maximum_speed);
            prep.ramp_type = RAMP_CRUISE;
            prep.current_speed = prep.maximum_speed;
          } else { // Mid-deceleration override ramp.
            prep.current_speed -= speed_var;
          }
          break;
        case RAMP_ACCEL:
          // NOTE: Acceleration ramp only computes during first do-while loop.
          speed_var = pl_block->acceleration*time_var;
@ -908,12 +954,10 @@ void st_prep_buffer()
        return; // Bail!
      } else { // End of planner block
        // The planner block is complete. All steps are set to be executed in the segment buffer.
-        #ifdef PARKING_ENABLE
+        if (sys.step_control & STEP_CONTROL_EXECUTE_SYS_MOTION) {
          if (sys.step_control & STEP_CONTROL_EXECUTE_PARK) { 
          bit_true(sys.step_control,STEP_CONTROL_END_MOTION);
          return;
        }
        #endif
        pl_block = NULL; // Set pointer to indicate check and load next planner block.
        plan_discard_current_block();
      }
@ -927,12 +971,10 @@ void st_prep_buffer()
 // however is not exactly the current speed, but the speed computed in the last step segment
 // in the segment buffer. It will always be behind by up to the number of segment blocks (-1)
 // divided by the ACCELERATION TICKS PER SECOND in seconds.
-#ifdef REPORT_REALTIME_RATE
+float st_get_realtime_rate()
-  float st_get_realtime_rate()
+{
-  {
+   if (sys.state & (STATE_CYCLE | STATE_HOMING | STATE_HOLD | STATE_JOG | STATE_SAFETY_DOOR)){
     if (sys.state & (STATE_CYCLE | STATE_HOMING | STATE_HOLD | STATE_MOTION_CANCEL | STATE_SAFETY_DOOR)){
     return prep.current_speed;
   }
  return 0.0f;
-  }
+}
 #endif
--- a/grbl/stepper.h
+++ b/grbl/stepper.h
@ -2,7 +2,7 @@
  stepper.h - stepper motor driver: executes motion plans of planner.c using the stepper motors
  Part of Grbl
-  Copyright (c) 2011-2015 Sungeun K. Jeon
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
  Copyright (c) 2009-2011 Simen Svale Skogsrud
  Grbl is free software: you can redistribute it and/or modify
@ -54,8 +54,6 @@ void st_prep_buffer();
 void st_update_plan_block_parameters();
 // Called by realtime status reporting if realtime rate reporting is enabled in config.h.
 #ifdef REPORT_REALTIME_RATE
 float st_get_realtime_rate();
 #endif
 #endif
--- a/grbl/system.c
+++ b/grbl/system.c
@ -2,7 +2,7 @@
  system.c - Handles system level commands and real-time processes
  Part of Grbl
-  Copyright (c) 2014-2015 Sungeun K. Jeon  
+  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -97,11 +97,12 @@ void system_execute_startup(char *line)
  uint8_t n;
  for (n=0; n < N_STARTUP_LINE; n++) {
    if (!(settings_read_startup_line(n, line))) {
-      report_status_message(STATUS_SETTING_READ_FAIL);
+      line[0] = 0;
      report_execute_startup_message(line,STATUS_SETTING_READ_FAIL);
    } else {
      if (line[0] != 0) {
-        printString(line); // Echo startup line to indicate execution.
+        uint8_t status_code = gc_execute_line(line);
-        report_status_message(gc_execute_line(line));
+        report_execute_startup_message(line,status_code);
      }
    }
  }
@ -123,9 +124,15 @@ uint8_t system_execute_line(char *line)
  float parameter, value;
  switch( line[char_counter] ) {
    case 0 : report_grbl_help(); break;
    case 'J' : // Jogging
      // Execute only if in IDLE or JOG states.
      if (sys.state != STATE_IDLE && sys.state != STATE_JOG) { return(STATUS_IDLE_ERROR); }
      if(line[2] != '=') { return(STATUS_INVALID_STATEMENT); }
      return(gc_execute_line(line)); // NOTE: $J= is ignored inside g-code parser and used to detect jog motions.
      break;
    case '$': case 'G': case 'C': case 'X':
-      if ( line[(char_counter+1)] != 0 ) { return(STATUS_INVALID_STATEMENT); }
+      if ( line[2] != 0 ) { return(STATUS_INVALID_STATEMENT); }
-      switch( line[char_counter] ) {
+      switch( line[1] ) {
        case '$' : // Prints Grbl settings
          if ( sys.state & (STATE_CYCLE | STATE_HOLD) ) { return(STATUS_IDLE_ERROR); } // Block during cycle. Takes too long to print.
          else { report_grbl_settings(); }
@ -156,26 +163,14 @@ uint8_t system_execute_line(char *line)
            // Don't run startup script. Prevents stored moves in startup from causing accidents.
          } // Otherwise, no effect.
          break;
    //  case 'J' : break;  // Jogging methods
          // TODO: Here jogging can be placed for execution as a seperate subprogram. It does not need to be 
          // susceptible to other realtime commands except for e-stop. The jogging function is intended to
          // be a basic toggle on/off with controlled acceleration and deceleration to prevent skipped 
          // steps. The user would supply the desired feedrate, axis to move, and direction. Toggle on would
          // start motion and toggle off would initiate a deceleration to stop. One could 'feather' the
          // motion by repeatedly toggling to slow the motion to the desired location. Location data would 
          // need to be updated real-time and supplied to the user through status queries.
          //   More controlled exact motions can be taken care of by inputting G0 or G1 commands, which are 
          // handled by the planner. It would be possible for the jog subprogram to insert blocks into the
          // block buffer without having the planner plan them. It would need to manage de/ac-celerations 
          // on its own carefully. This approach could be effective and possibly size/memory efficient.  
      }
      break;
    default :
      // Block any system command that requires the state as IDLE/ALARM. (i.e. EEPROM, homing)
      if ( !(sys.state == STATE_IDLE || sys.state == STATE_ALARM) ) { return(STATUS_IDLE_ERROR); }
-      switch( line[char_counter] ) {
+      switch( line[1] ) {
        case '#' : // Print Grbl NGC parameters
-          if ( line[++char_counter] != 0 ) { return(STATUS_INVALID_STATEMENT); }
+          if ( line[2] != 0 ) { return(STATUS_INVALID_STATEMENT); }
          else { report_ngc_parameters(); }
          break;
        case 'H' : // Perform homing cycle [IDLE/ALARM]
@ -191,10 +186,15 @@ uint8_t system_execute_line(char *line)
            }
          } else { return(STATUS_SETTING_DISABLED); }
          break;
        case 'S' : // Puts Grbl to sleep [IDLE/ALARM]
          if ((line[2] != 'L') || (line[3] != 'P') || (line[4] != 0)) { return(STATUS_INVALID_STATEMENT); }
          system_set_exec_state_flag(EXEC_SLEEP); // Set to execute sleep mode immediately
          break;
        case 'I' : // Print or store build info. [IDLE/ALARM]
          if ( line[++char_counter] == 0 ) {
            settings_read_build_info(line);
            report_build_info(line);
          #ifdef ENABLE_BUILD_INFO_WRITE_COMMAND
            } else { // Store startup line [IDLE/ALARM]
              if(line[char_counter++] != '=') { return(STATUS_INVALID_STATEMENT); }
              helper_var = char_counter; // Set helper variable as counter to start of user info line.
@ -202,17 +202,21 @@ uint8_t system_execute_line(char *line)
                line[char_counter-helper_var] = line[char_counter];
              } while (line[char_counter++] != 0);
              settings_store_build_info(line);
          #endif
          }
          break;
        case 'R' : // Restore defaults [IDLE/ALARM]
-          if (line[++char_counter] != 'S') { return(STATUS_INVALID_STATEMENT); }
+          if ((line[2] != 'S') || (line[3] != 'T') || (line[4] != '=') || (line[6] != 0)) { return(STATUS_INVALID_STATEMENT); }
-          if (line[++char_counter] != 'T') { return(STATUS_INVALID_STATEMENT); }
+          switch (line[5]) {
-          if (line[++char_counter] != '=') { return(STATUS_INVALID_STATEMENT); }
+            #ifdef ENABLE_RESTORE_EEPROM_DEFAULT_SETTINGS
          if (line[char_counter+2] != 0) { return(STATUS_INVALID_STATEMENT); }                        
          switch (line[++char_counter]) {
              case '$': settings_restore(SETTINGS_RESTORE_DEFAULTS); break;
            #endif
            #ifdef ENABLE_RESTORE_EEPROM_CLEAR_PARAMETERS
              case '#': settings_restore(SETTINGS_RESTORE_PARAMETERS); break;
            #endif
            #ifdef ENABLE_RESTORE_EEPROM_WIPE_ALL
              case '*': settings_restore(SETTINGS_RESTORE_ALL); break;
            #endif
            default: return(STATUS_INVALID_STATEMENT);
          }
          report_feedback_message(MESSAGE_RESTORE_DEFAULTS);
@ -260,6 +264,16 @@ uint8_t system_execute_line(char *line)
 }
 void system_flag_wco_change()
 {
  #ifdef FORCE_BUFFER_SYNC_DURING_WCO_CHANGE
    protocol_buffer_synchronize();
  #endif
  sys.report_wco_counter = REPORT_WCO_REFRESH_BUSY_COUNT;
 }
 // Returns machine position of axis 'idx'. Must be sent a 'step' array.
 // NOTE: If motor steps and machine position are not in the same coordinate frame, this function
 //   serves as a central place to compute the transformation.
@ -267,10 +281,10 @@ float system_convert_axis_steps_to_mpos(int32_t *steps, uint8_t idx)
 {
  float pos;
  #ifdef COREXY
-    if (idx==A_MOTOR) { 
+    if (idx==X_AXIS) {
-      pos = 0.5*((steps[A_MOTOR] + steps[B_MOTOR])/settings.steps_per_mm[idx]);
+      pos = (float)system_convert_corexy_to_x_axis_steps(steps) / settings.steps_per_mm[idx];
-    } else if (idx==B_MOTOR) {
+    } else if (idx==Y_AXIS) {
-      pos = 0.5*((steps[A_MOTOR] - steps[B_MOTOR])/settings.steps_per_mm[idx]);
+      pos = (float)system_convert_corexy_to_y_axis_steps(steps) / settings.steps_per_mm[idx];
    } else {
      pos = steps[idx]/settings.steps_per_mm[idx];
    }
@ -291,6 +305,41 @@ void system_convert_array_steps_to_mpos(float *position, int32_t *steps)
 }
 // CoreXY calculation only. Returns x or y-axis "steps" based on CoreXY motor steps.
 #ifdef COREXY
  int32_t system_convert_corexy_to_x_axis_steps(int32_t *steps)
  {
    return( (steps[A_MOTOR] + steps[B_MOTOR])/2 );
  }
  int32_t system_convert_corexy_to_y_axis_steps(int32_t *steps)
  {
    return( (steps[A_MOTOR] - steps[B_MOTOR])/2 );
  }
 #endif
 // Checks and reports if target array exceeds machine travel limits.
 uint8_t system_check_travel_limits(float *target)
 {
  uint8_t idx;
  for (idx=0; idx<N_AXIS; idx++) {
    #ifdef HOMING_FORCE_SET_ORIGIN
      // When homing forced set origin is enabled, soft limits checks need to account for directionality.
      // NOTE: max_travel is stored as negative
      if (bit_istrue(settings.homing_dir_mask,bit(idx))) {
        if (target[idx] < 0 || target[idx] > -settings.max_travel[idx]) { return(true); }
      } else {
        if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { return(true); }
      }
    #else
      // NOTE: max_travel is stored as negative
      if (target[idx] > 0 || target[idx] < settings.max_travel[idx]) { return(true); }
    #endif
  }
  return(false);
 }
 // Special handlers for setting and clearing Grbl's real-time execution flags.
 void system_set_exec_state_flag(uint8_t mask) {
  uint8_t sreg = SREG;
@ -306,10 +355,10 @@ void system_clear_exec_state_flag(uint8_t mask) {
  SREG = sreg;
 }
-void system_set_exec_alarm_flag(uint8_t mask) {
+void system_set_exec_alarm(uint8_t code) {
  uint8_t sreg = SREG;
  cli();
-  sys_rt_exec_alarm |= (mask);
+  sys_rt_exec_alarm = code;
  SREG = sreg;
 }
@ -319,3 +368,31 @@ void system_clear_exec_alarm_flag(uint8_t mask) {
  sys_rt_exec_alarm &= ~(mask);
  SREG = sreg;
 }
 void system_set_exec_motion_override_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_motion_override |= (mask);
  SREG = sreg;
 }
 void system_set_exec_accessory_override_flag(uint8_t mask) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_accessory_override |= (mask);
  SREG = sreg;
 }
 void system_clear_exec_motion_overrides() {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_motion_override = 0;
  SREG = sreg;
 }
 void system_clear_exec_accessory_overrides() {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_accessory_override = 0;
  SREG = sreg;
 }
--- a/grbl/system.h
+++ b/grbl/system.h
@ -2,7 +2,7 @@
  system.h - Header for system level commands and real-time processes
  Part of Grbl
-  Copyright (c) 2014-2015 Sungeun K. Jeon  
+  Copyright (c) 2014-2016 Sungeun K. Jeon for Gnea Research LLC
  Grbl is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
@ -35,17 +35,39 @@
 #define EXEC_RESET          bit(4) // bitmask 00010000
 #define EXEC_SAFETY_DOOR    bit(5) // bitmask 00100000
 #define EXEC_MOTION_CANCEL  bit(6) // bitmask 01000000
 #define EXEC_SLEEP          bit(7) // bitmask 10000000
-// Alarm executor bit map.
+// Alarm executor codes. Valid values (1-255). Zero is reserved.
-// NOTE: EXEC_CRITICAL_EVENT is an optional flag that must be set with an alarm flag. When enabled,
+#define EXEC_ALARM_HARD_LIMIT           1
-// this halts Grbl into an infinite loop until the user aknowledges the problem and issues a soft-
+#define EXEC_ALARM_SOFT_LIMIT           2
-// reset command. For example, a hard limit event needs this type of halt and aknowledgement.
+#define EXEC_ALARM_ABORT_CYCLE          3
-#define EXEC_CRITICAL_EVENT     bit(0) // bitmask 00000001 (SPECIAL FLAG. See NOTE:)
+#define EXEC_ALARM_PROBE_FAIL_INITIAL   4
-#define EXEC_ALARM_HARD_LIMIT   bit(1) // bitmask 00000010
+#define EXEC_ALARM_PROBE_FAIL_CONTACT   5
-#define EXEC_ALARM_SOFT_LIMIT   bit(2) // bitmask 00000100
+#define EXEC_ALARM_HOMING_FAIL_RESET    6
-#define EXEC_ALARM_ABORT_CYCLE  bit(3) // bitmask 00001000
+#define EXEC_ALARM_HOMING_FAIL_DOOR     7
-#define EXEC_ALARM_PROBE_FAIL   bit(4) // bitmask 00010000
+#define EXEC_ALARM_HOMING_FAIL_PULLOFF  8
-#define EXEC_ALARM_HOMING_FAIL  bit(5) // bitmask 00100000
+#define EXEC_ALARM_HOMING_FAIL_APPROACH 9
 // Override bit maps. Realtime bitflags to control feed, rapid, spindle, and coolant overrides.
 // Spindle/coolant and feed/rapids are separated into two controlling flag variables.
 #define EXEC_FEED_OVR_RESET         bit(0)
 #define EXEC_FEED_OVR_COARSE_PLUS   bit(1)
 #define EXEC_FEED_OVR_COARSE_MINUS  bit(2)
 #define EXEC_FEED_OVR_FINE_PLUS     bit(3)
 #define EXEC_FEED_OVR_FINE_MINUS    bit(4)
 #define EXEC_RAPID_OVR_RESET        bit(5)
 #define EXEC_RAPID_OVR_MEDIUM       bit(6)
 #define EXEC_RAPID_OVR_LOW          bit(7)
 // #define EXEC_RAPID_OVR_EXTRA_LOW   bit(*) // *NOT SUPPORTED*
 #define EXEC_SPINDLE_OVR_RESET         bit(0)
 #define EXEC_SPINDLE_OVR_COARSE_PLUS   bit(1)
 #define EXEC_SPINDLE_OVR_COARSE_MINUS  bit(2)
 #define EXEC_SPINDLE_OVR_FINE_PLUS     bit(3)
 #define EXEC_SPINDLE_OVR_FINE_MINUS    bit(4)
 #define EXEC_SPINDLE_OVR_STOP          bit(5)
 #define EXEC_COOLANT_FLOOD_OVR_TOGGLE  bit(6)
 #define EXEC_COOLANT_MIST_OVR_TOGGLE   bit(7)
 // Define system state bit map. The state variable primarily tracks the individual functions
 // of Grbl to manage each without overlapping. It is also used as a messaging flag for
@ -56,8 +78,9 @@
 #define STATE_HOMING        bit(2) // Performing homing cycle
 #define STATE_CYCLE         bit(3) // Cycle is running or motions are being executed.
 #define STATE_HOLD          bit(4) // Active feed hold
-#define STATE_SAFETY_DOOR   bit(5) // Safety door is ajar. Feed holds and de-energizes system.
+#define STATE_JOG           bit(5) // Jogging mode.
-#define STATE_MOTION_CANCEL bit(6) // Motion cancel by feed hold and return to idle. 
+#define STATE_SAFETY_DOOR   bit(6) // Safety door is ajar. Feed holds and de-energizes system.
 #define STATE_SLEEP         bit(7) // Sleep state.
 // Define system suspend flags. Used in various ways to manage suspend states and procedures.
 #define SUSPEND_DISABLE           0      // Must be zero.
@ -66,15 +89,16 @@
 #define SUSPEND_RETRACT_COMPLETE  bit(2) // (Safety door only) Indicates retraction and de-energizing is complete.
 #define SUSPEND_INITIATE_RESTORE  bit(3) // (Safety door only) Flag to initiate resume procedures from a cycle start.
 #define SUSPEND_RESTORE_COMPLETE  bit(4) // (Safety door only) Indicates ready to resume normal operation.
-#define SUSPEND_SAFETY_DOOR_AJAR  bit(5) // Indicates suspend was initiated by a safety door state.
+#define SUSPEND_SAFETY_DOOR_AJAR  bit(5) // Tracks safety door state for resuming.
 #define SUSPEND_MOTION_CANCEL     bit(6) // Indicates a canceled resume motion. Currently used by probing routine.
 #define SUSPEND_JOG_CANCEL        bit(7) // Indicates a jog cancel in process and to reset buffers when complete.
 // Define step segment generator state flags.
 #define STEP_CONTROL_NORMAL_OP            0
-// #define STEP_CONTROL_RECOMPUTE_ACTIVE_BLOCK bit(0)
+#define STEP_CONTROL_END_MOTION           bit(0)
-#define STEP_CONTROL_END_MOTION             bit(1)
+#define STEP_CONTROL_EXECUTE_HOLD         bit(1)
-#define STEP_CONTROL_EXECUTE_HOLD           bit(2)
+#define STEP_CONTROL_EXECUTE_SYS_MOTION   bit(2)
-#define STEP_CONTROL_EXECUTE_PARK           bit(3)
+#define STEP_CONTROL_UPDATE_SPINDLE_PWM   bit(3)
 // Define control pin index for Grbl internal use. Pin maps may change, but these values don't.
 #ifdef ENABLE_SAFETY_DOOR_INPUT_PIN
@ -90,28 +114,49 @@
  #define CONTROL_PIN_INDEX_CYCLE_START   bit(2)
 #endif
 // Define toggle override control states.
 #define TOGGLE_OVR_STOP_ENABLED        bit(0)
 #define TOGGLE_OVR_STOP_INITIATE       bit(1)
 #define TOGGLE_OVR_STOP_RESTORE        bit(2)
 #define TOGGLE_OVR_STOP_RESTORE_CYCLE  bit(3)
 #define TOGGLE_OVR_FLOOD_COOLANT       bit(4)
 #define TOGGLE_OVR_MIST_COOLANT        bit(5)
 #define TOGGLE_OVR_STOP_ACTIVE_MASK  (TOGGLE_OVR_STOP_ENABLED|TOGGLE_OVR_STOP_INITIATE|TOGGLE_OVR_STOP_RESTORE|TOGGLE_OVR_STOP_RESTORE_CYCLE)
 // NOTE: Mask is used to determine if spindle stop is active or disabled.
 // Define global system variables
 typedef struct {
  uint8_t abort;               // System abort flag. Forces exit back to main loop for reset.
-  uint8_t state;                 // Tracks the current state of Grbl.
+  uint8_t state;               // Tracks the current system state of Grbl.
  uint8_t suspend;             // System suspend bitflag variable that manages holds, cancels, and safety door.
-  uint8_t soft_limit;            // Tracks soft limit errors for the state machine (Boolean)
+  uint8_t soft_limit;          // Tracks soft limit errors for the state machine. (boolean)
-  uint8_t step_control;
+  uint8_t step_control;        // Governs the step segment generator depending on system state.
  int32_t position[N_AXIS];      // Real-time machine (aka home) position vector in steps. 
                                 // NOTE: This may need to be a volatile variable, if problems arise.                             
  int32_t probe_position[N_AXIS]; // Last probe position in machine coordinates and steps.
  uint8_t probe_succeeded;     // Tracks if last probing cycle was successful.
  uint8_t homing_axis_lock;    // Locks axes when limits engage. Used as an axis motion mask in the stepper ISR.
  uint8_t f_override;          // Feed rate override value in percent
  uint8_t r_override;          // Rapids override value in percent
  uint8_t spindle_speed_ovr;   // Spindle speed value in percent
  uint8_t toggle_ovr_mask;          // Tracks toggle override states
  uint8_t report_ovr_counter;  // Tracks when to add override data to status reports.
  uint8_t report_wco_counter;  // Tracks when to add work coordinate offset data to status reports.
 } system_t;
 extern system_t sys;
 // NOTE: These position variables may need to be declared as volatiles, if problems arise.
 int32_t sys_position[N_AXIS];      // Real-time machine (aka home) position vector in steps.
 int32_t sys_probe_position[N_AXIS]; // Last probe position in machine coordinates and steps.
 volatile uint8_t sys_probe_state;  // Probing state value.  Used to coordinate the probing cycle with stepper ISR.
 volatile uint8_t sys_rt_exec_state;   // Global realtime executor bitflag variable for state management. See EXEC bitmasks.
 volatile uint8_t sys_rt_exec_alarm;   // Global realtime executor bitflag variable for setting various alarms.
 volatile uint8_t sys_rt_exec_motion_override; // Global realtime executor bitflag variable for motion-based overrides.
 volatile uint8_t sys_rt_exec_accessory_override; // Global realtime executor bitflag variable for spindle/coolant overrides.
 #ifdef DEBUG
  #define EXEC_DEBUG_REPORT  bit(0)
  volatile uint8_t sys_rt_exec_debug;
 #endif
 // Initialize the serial protocol
 void system_init();
@ -128,17 +173,33 @@ uint8_t system_execute_line(char *line);
 // Execute the startup script lines stored in EEPROM upon initialization
 void system_execute_startup(char *line);
 void system_flag_wco_change();
 // Returns machine position of axis 'idx'. Must be sent a 'step' array.
 float system_convert_axis_steps_to_mpos(int32_t *steps, uint8_t idx);
 // Updates a machine 'position' array based on the 'step' array sent.
 void system_convert_array_steps_to_mpos(float *position, int32_t *steps);
 // CoreXY calculation only. Returns x or y-axis "steps" based on CoreXY motor steps.
 #ifdef COREXY
  int32_t system_convert_corexy_to_x_axis_steps(int32_t *steps);
  int32_t system_convert_corexy_to_y_axis_steps(int32_t *steps);
 #endif
 // Checks and reports if target array exceeds machine travel limits.
 uint8_t system_check_travel_limits(float *target);
 // Special handlers for setting and clearing Grbl's real-time execution flags.
 void system_set_exec_state_flag(uint8_t mask);
 void system_clear_exec_state_flag(uint8_t mask);
-void system_set_exec_alarm_flag(uint8_t mask);
+void system_set_exec_alarm(uint8_t code);
 void system_clear_exec_alarm_flag(uint8_t mask);
 void system_set_exec_motion_override_flag(uint8_t mask);
 void system_set_exec_accessory_override_flag(uint8_t mask);
 void system_clear_exec_motion_overrides();
 void system_clear_exec_accessory_overrides();
 #endif