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.

doc/csv/alarm_codes.csv

@@ -0,0 +1,9 @@
+1,Hard limit,Hard limit has been triggered. Machine position is likely lost due to sudden stop. Re-homing is highly recommended.
+2,Soft limit,G-code motion target exceeds machine travel. Machine position safely retained. Alarm may be unlocked.
+3,Abort during cycle,Reset while in motion. Grbl cannot guarantee position. Lost steps are likely. Re-homing is highly recommended.
+4,Probe fail,If 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,If the probe fails to contact the workpiece within the programmed travel for G38.2 and G38.4.
+6,Homing fail,If the active homing cycle was reset.
+7,Homing fail,If the safety door was opened during homing cycle.
+8,Homing fail,Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring.
+9,Homing fail,Failed to find limit switch within travel. Defined as `1.5 * max_travel` on search and `5 * pulloff` on locate phases.

doc/csv/error_codes.csv

@@ -0,0 +1,34 @@
+1,Expected command letter,G-code words consist of a letter and a value. Letter was not found.
+2,Bad number format,Numeric value format is not valid or missing an expected value.
+3,Invalid statement,Grbl '$' system command was not recognized or supported.
+4,Value < 0`,Negative value received for an expected positive value.
+5,Setting disabled,Homing cycle is not enabled via settings.
+6,Value < 3 usec,Minimum step pulse time must be greater than 3usec.
+7,EEPROM read fail. Using defaults,EEPROM read failed. Reset and restored to default values.
+8,Not idle,Grbl '$' command cannot be used unless Grbl is IDLE. Ensures smooth operation during a job.
+9,G-code lock,G-code 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. Line was not processed and executed.
+12,Step rate > 30kHz,Grbl '$' setting value exceeds the maximum step rate 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.
+15,Travel exceeded,Jog target exceeds machine travel. Command ignored.
+16,Invalid jog command,Jog command with 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 mode 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,Work coordinate system commanded not supported.
+30,Invalid gcode ID:30,G53 only allowed during G0 and G1 motion modes.
+31,Invalid gcode ID:31,Axis words found in block while no command uses them.
+32,Invalid gcode ID:32,G2/3 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,G2/3 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 assigned to wrong axis.

doc/markdown/error_codes.md

@@ -0,0 +1,124 @@
+## Meanings of Grbl messages and error/alarm codes
+
+
+#### _'error:' Codes_
+
+Format - `(v1.0)` `:` `(v0.9)` - `Description`
+
+- `error:1` : `error: Expected command letter` - G-code words consist of a letter and a value. Letter was not found.
+
+- `error:2` : `error: Bad number format` - Numeric value format is not valid or missing an expected value.
+
+- `error:3` : `error: Invalid statement` - Grbl '$' system command was not recognized or supported
+
+- `error:4` : `error: Value < 0` - Negative value received for an expected positive value.
+
+- `error:5` : `error: Setting disabled` - Homing cycle is not enabled via settings.
+
+- `error:6` : `error: Value < 3 usec` - Minimum step pulse time must be greater than 3usec
+
+- `error:7` : `error: EEPROM read fail. Using defaults` - EEPROM read failed. Reset and restored to default values.
+
+- `error:8` : `error: Not idle` - Grbl '$' command cannot be used unless Grbl is IDLE. Ensures smooth operation during a job.
+
+- `error:9` : `error: G-code lock` - G-code locked out during alarm or jog state
+
+- `error:10` : `error: Homing not enabled` - Soft limits cannot be enabled without homing also enabled.
+
+- `error:11` : `error: Line overflow` - Max characters per line exceeded. Line was not processed and executed.
+
+- `error:12` : `error: Step rate > 30kHz`* - Grbl '$' setting value exceeds the maximum step rate supported.
+
+- `error:13` : `error: Check Door` - Safety door detected as opened and door state initiated.
+
+- `error:14` : `error: Line length exceeded` - (Grbl-Mega Only) Build info or startup line exceeded EEPROM line length limit.
+
+- `error:15` : `error: Travel exceeded` - Jog target exceeds machine travel. Command ignored.
+
+- `error:16` : `error: Invalid jog command` - Jog command with no '=' or contains prohibited g-code.
+
+- `error:20` : `error: Unsupported command` - Unsupported or invalid g-code command found in block.
+
+- `error:21` : `error: Modal group violation` - More than one g-code command from same modal group found in block.
+
+- `error:22` : `error: Undefined feed rate` - Feed rate has not yet been set or is undefined.
+
+- `error:23` : `error: Invalid gcode ID:23` - G-code command in block requires an integer value.
+
+- `error:24` : `error: Invalid gcode ID:24` - More than one g-code command that requires axis words found in block.
+
+- `error:25` : `error: Invalid gcode ID:25` - Repeated g-code word found in block.
+
+- `error:26` : `error: Invalid gcode ID:26` - No axis words found in block for g-code command or mode which requires them.
+
+- `error:27` : `error: Invalid gcode ID:27` - Line number value is invalid
+
+- `error:28` : `error: Invalid gcode ID:28` - G-code command is missing a required value word.
+
+- `error:29` : `error: Invalid gcode ID:29` - Work coordinate system commanded not supported.
+
+- `error:30` : `error: Invalid gcode ID:30` - G53 only allowed during G0 and G1 motion modes.
+
+- `error:31` : `error: Invalid gcode ID:31` - Axis words found in block while no command uses them.
+
+- `error:32` : `error: Invalid gcode ID:32` - G2/3 arcs require at least one in-plane axis word.
+
+- `error:33` : `error: Invalid gcode ID:33` - Motion command target is invalid.
+
+- `error:34` : `error: Invalid gcode ID:34` - Arc radius value is invalid.
+
+- `error:35` : `error: Invalid gcode ID:35` - G2/3 arcs require at least one in-plane offset word.
+
+- `error:36` : `error: Invalid gcode ID:36` - Unused value words found in block.
+
+- `error:37` : `error: Invalid gcode ID:37` - G43.1 dynamic tool length offset assigned to wrong axis.
+
+`*` indicates feedback enabled only by compile-time option.
+
+-----
+
+#### 'Alarm:' Codes
+
+Format - `(v1.0)` `:` `(v0.9)` - `Description`
+
+- `ALARM:1` : `ALARM: Hard limit` - Hard limit has been triggered. Machine position is likely lost due to sudden stop. Re-homing is highly recommended.
+`
+- `ALARM:2` : `ALARM: Soft limit` - G-code motion target exceeds machine travel. Machine position safely retained. Alarm may be unlocked.
+
+- `ALARM:3` : `ALARM: Abort during cycle` - Reset while in motion. Grbl cannot guarantee position. Lost steps are likely. Re-homing is highly recommended.
+
+- `ALARM:4` : `ALARM: Probe fail` - If 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.
+
+- `ALARM:5` : `ALARM: Probe fail` - If the probe fails to contact the workpiece within the programmed travel for G38.2 and G38.4.
+
+- `ALARM:6` : `ALARM: Homing fail` - If the active homing cycle was reset.
+
+- `ALARM:7` : `ALARM: Homing fail` - If the safety door was opened during homing cycle.
+
+- `ALARM:8` : `ALARM: Homing fail` - Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring.
+
+- `ALARM:9` : `ALARM: Homing fail` - Failed to find limit switch within travel. Defined as `1.5 * max_travel` on search and `5 * pulloff` on locate phases.
+
+-----
+
+#### Message Descriptions
+
+Format - `Message` - `Description`
+
+- `[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. Hard or soft limit errors will trigger this event.
+
+- `[‘$H’|’$X’ to unlock]`- Alarm message at initialization. All g-code commands and some ‘$’ are blocked until unlocked via homing or $X.
+
+- `[Caution: Unlocked]` - Alarm unlock $X acknowledgement.
+
+- `[Enabled]` - Indicates Grbl’s check-mode is enabled.
+
+- `[Disabled]` - Indicates Grbl’s check-mode is disabled. Grbl is automatically reset afterwards.
+
+- `[Check Door]` - Safety door detected as open. This message appears either immediately upon a safety door ajar or if the safety is open when Grbl initializes after a power-up/reset.
+
+- `[Check Limits]` - If Grbl detects a limit switch is triggered after power-up/reset and hard limits are enabled, this will appear as a courtesy message.
+
+- `[Pgm End]` - M2/30 program end message to denote g-code modes have been restored to defaults according to the M2/30 g-code description.
+
+- `[Restoring defaults]` - Acknowledgement message when restoring EEPROM defaults via a `$RST=` command.

doc/markdown/jogging.md

@@ -0,0 +1,41 @@
+## Grbl v1.0 Jogging
+
+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 feed hold command. Grbl
+  will automatically flush Grbl's internal buffers of any queued jogging motions and return
+  to the 'Idle' state. No soft-reset required.
+- 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.

doc/markdown/realtime_cmds.md

@@ -0,0 +1,135 @@
+## Grbl v1.0 Realtime commands
+
+Realtime commands are single control characters that may be sent to Grbl to command and perform an action in real-time, regardless of what Grbl is doing at the time. These commands include a reset, feed hold, resume, status report query, and overrides (in v1.0).
+
+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 carraige return after them.
+
+- Is not considered a part of the streaming protocol.
+
+- 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
+The normal ASCII realtime command characters used in Grbl v0.9 have been retained in Grbl v1.0 and are described below for completeness.
+
+- `0x18` (ctrl-x) : Soft-Reset
+
+  - Immediately halts and resets Grbl.
+  - 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.
+  - 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 v1.0 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 readily 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.
+  - 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.
+
+
+- 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.
+    - The command is otherwise ignored, especially while in motion. This prevents accidental disabling during a job that can either destroy the part/machine or 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 supercede 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.

doc/markdown/report.md

@@ -0,0 +1,279 @@
+### _Grbl v1.0 Realtime Status Reports_ (Rev. 2)
+
+--------
+
+#### Summary of Changes from Grbl v0.9 Reports
+
+- 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 v1.0 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:0,0`. The first value is planner blocks in use and the second is RX bytes in use.
+
+
+- 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.)
+
+-------
+
+#### Basic Characteristics
+
+- 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`
+
+      - 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:0,0`. The first value is planner blocks in use and the second is RX bytes in use.
+
+        - This data field will not appear if:
+
+          - It is disabled by the `$` status report mask setting.
+
+    - **Line Number:**
+
+        - `Ln:99999` indicates line 99999 is currently being executed. This differs from the `$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.