Settings refactoring. Bug fixes. Misc new features.

This is likely the last major change to the v0.9 code base before push
to master. Only two minor things remain on the agenda (CoreXY support,
force clear EEPROM, and an extremely low federate bug).

- NEW! Grbl is now compile-able and may be flashed directly through the
Arduino IDE. Only minor changes were required for this compatibility.
See the Wiki to learn how to do it.

- New status reporting mask to turn on and off what Grbl sends back.
This includes machine coordinates, work coordinates, serial RX buffer
usage, and planner buffer usage. Expandable to more information on user
request, but that’s it for now.

- Settings have been completely renumbered to allow for future new
settings to be installed without having to constantly reshuffle and
renumber all of the settings every time.

- All settings masks have been standardized to mean bit 0 = X, bit 1 =
Y, and bit 2 = Z, to reduce confusion on how they work. The invert
masks used by the internal Grbl system were updated to accommodate this
change as well.

- New invert probe pin setting, which does what it sounds like.

- Fixed a probing cycle bug, where it would freeze intermittently, and
removed some redundant code.

- Homing may now be set to the origin wherever the limit switches are.
Traditionally machine coordinates should always be in negative space,
but when limit switches on are on the opposite side, the machine
coordinate would be set to -max_travel for the axis. Now you can always
make it [0,0,0] via a compile-time option in config.h. (Soft limits
routine was updated to account for this as well.)

 - Probe coordinate message immediately after a probing cycle may now
be turned off via a compile-time option in config.h. By default the
probing location is always reported.

- Reduced the N_ARC_CORRECTION default value to reflect the changes in
how circles are generated by an arc tolerance, rather than a fixed arc
segment setting.

- Increased the incoming line buffer limit from 70 to 80 characters.
Had some extra memory space to invest into this.

- Fixed a bug where tool number T was not being tracked and reported
correctly.

- Added a print free memory function for debugging purposes. Not used
otherwise.

- Realtime rate report should now work during feed holds, but it hasn’t
been tested yet.

- Updated the streaming scripts with MIT-license and added the simple
streaming to the main stream.py script to allow for settings to be sent.

- Some minor code refactoring to improve flash efficiency. Reduced the
flash by several hundred KB, which was re-invested in some of these new
features.

config.h

@@ -27,6 +27,8 @@
 
 #ifndef config_h
 #define config_h
+#include <system.h>
+
 
 // Default settings. Used when resetting EEPROM. Change to desired name in defaults.h
 #define DEFAULTS_GENERIC
@@ -78,6 +80,11 @@
 // greater.
 #define N_HOMING_LOCATE_CYCLE 2 // Integer (1-128)
 
+// After homing, Grbl will set by default the entire machine space into negative space, as is typical
+// for professional CNC machines, regardless of where the limit switches are located. Uncomment this 
+// define to force Grbl to always set the machine origin at the homed location despite switch orientation.
+// #define HOMING_FORCE_SET_ORIGIN // Uncomment to enable.
+
 // Number of blocks Grbl executes upon startup. These blocks are stored in EEPROM, where the size
 // and addresses are defined in settings.h. With the current settings, up to 3 startup blocks may
 // be stored and executed in order. These startup blocks would typically be used to set the g-code
@@ -103,6 +110,11 @@
 // 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.
+#define MESSAGE_PROBE_COORDINATES // Enabled by default. Comment to disable.
  
 // Enables a second coolant control pin via the mist coolant g-code command M7 on the Arduino Uno
 // analog pin 5. Only use this option if you require a second coolant control pin.
@@ -156,12 +168,10 @@
 #define MINIMUM_JUNCTION_SPEED 0.0 // (mm/min)
 
 // Number of arc generation iterations by small angle approximation before exact arc trajectory 
-// correction. This parameter maybe decreased if there are issues with the accuracy of the arc
-// generations. In general, the default value is more than enough for the intended CNC applications
-// of grbl, and should be on the order or greater than the size of the buffer to help with the 
-// computational efficiency of generating arcs.
-// NOTE: Arcs are now generated by a chordal tolerance
-#define N_ARC_CORRECTION 20 // Integer (1-255)
+// correction with expensive sin() and cos() calcualtions. This parameter maybe decreased if there 
+// are issues with the accuracy of the arc generations, or increased if arc execution is getting
+// bogged down by too many trig calculations. 
+#define N_ARC_CORRECTION 12 // Integer (1-255)
 
 // Time delay increments performed during a dwell. The default value is set at 50ms, which provides
 // a maximum time delay of roughly 55 minutes, more than enough for most any application. Increasing
@@ -200,11 +210,11 @@
 // each of the startup blocks, as they are each stored as a string of this size. Make sure
 // to account for the available EEPROM at the defined memory address in settings.h and for
 // the number of desired startup blocks.
-// NOTE: 70 characters is not a problem except for extreme cases, but the line buffer size 
+// NOTE: 80 characters is not a problem except for extreme cases, but the line buffer size 
 // can be too small and g-code blocks can get truncated. Officially, the g-code standards 
 // support up to 256 characters. In future versions, this default will be increased, when 
 // we know how much extra memory space we can re-invest into this.
-// #define LINE_BUFFER_SIZE 70  // Uncomment to override default in protocol.h
+// #define LINE_BUFFER_SIZE 80  // Uncomment to override default in protocol.h
   
 // Serial send and receive buffer size. The receive buffer is often used as another streaming
 // buffer to store incoming blocks to be processed by Grbl when its ready. Most streaming
@@ -212,6 +222,7 @@
 // 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.
 // #define RX_BUFFER_SIZE 128 // Uncomment to override defaults in serial.h
 // #define TX_BUFFER_SIZE 64
   
@@ -246,4 +257,6 @@
 // #endif
 
 // ---------------------------------------------------------------------------------------
+
+
 #endif