Untested! Soft limits, max travel, homing changes, new settings.

- WARNING: Completely untested. Will later when there is time. Settings
WILL be overwritten, as there are new settings.

- Soft limits installed. Homing must be enabled for soft limits to work
correctly. Errors out much like a hard limit, locking out everything
and bringing up the alarm mode. Only difference is it forces a feed
hold before doing so. Position is not lost.

- IMPORTANT: Homing had to be updated so that soft limits work better
with less CPU overhead. When homing completes, all axes are assumed to
exist in negative space. If your limit switch is other side, the homing
cycle with set this axis location to the max travel value, rather than
zero.

- Update mc_line() to accept an array, rather than individual variables.

- Added an mc_auto_cycle_start() function handle this feature.
Organization only.

-

config.h

@@ -3,7 +3,7 @@
   Part of Grbl
 
   Copyright (c) 2009-2011 Simen Svale Skogsrud
-  Copyright (c) 2011-2012 Sungeun K. Jeon
+  Copyright (c) 2011-2013 Sungeun K. Jeon
 
   Grbl is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -107,13 +107,12 @@
 
 // The "Stepper Driver Interrupt" employs the Pramod Ranade inverse time algorithm to manage the
 // Bresenham line stepping algorithm. The value ISR_TICKS_PER_SECOND is the frequency(Hz) at which
-// the Ranade algorithm ticks at. Maximum step frequencies are limited by the Ranade frequency by
-// approximately 0.75-0.9 * ISR_TICK_PER_SECOND. Meaning for 20kHz, the max step frequency is roughly
-// 15-18kHz. An Arduino can safely complete a single interrupt of the current stepper driver algorithm 
-// theoretically up to a frequency of 35-40kHz, but CPU overhead increases exponentially as this
-// frequency goes up. So there will be little left for other processes like arcs.  
-//   In future versions, more work will be done to increase the step rates but still stay around
-// 20kHz by performing two steps per step event, rather than just one.
+// the Ranade algorithm ticks at. Recommended step frequencies are limited by the Ranade frequency by
+// approximately 0.75-0.9 * ISR_TICK_PER_SECOND. Meaning for 30kHz, the max step frequency is roughly
+// 22.5-27kHz, but 30kHz is still possible, just not optimal. An Arduino can safely complete a single
+// interrupt of the current stepper driver algorithm theoretically up to a frequency of 35-40kHz, but 
+// CPU overhead increases exponentially as this frequency goes up. So there will be little left for 
+// other processes like arcs.  
 #define ISR_TICKS_PER_SECOND 30000L  // Integer (Hz)
 
 // The temporal resolution of the acceleration management subsystem. Higher number give smoother
@@ -208,7 +207,7 @@
 
 // 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 Teensy or Sanguino. Or decrease if the Arduino
+// available RAM, like when re-compiling for a Mega or Sanguino. Or decrease if the Arduino
 // begins to crash due to the lack of available RAM or if the CPU is having trouble keeping
 // up with planning new incoming motions as they are executed. 
 // #define BLOCK_BUFFER_SIZE 18  // Uncomment to override default in planner.h.