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.

-

limits.c

@@ -3,7 +3,7 @@
   Part of Grbl
 
   Copyright (c) 2009-2011 Simen Svale Skogsrud
-  Copyright (c) 2012 Sungeun K. Jeon
+  Copyright (c) 2012-2013 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
@@ -244,3 +244,29 @@ void limits_go_home()
 
   st_go_idle(); // Call main stepper shutdown routine.  
 }
+
+
+// Performs a soft limit check. Called from mc_line() only. Assumes the machine has been homed,
+// and the workspace volume is in all negative space.
+void limits_soft_check(float *target)
+{
+  if ( target[X_AXIS] > 0 || target[X_AXIS] < -settings.max_travel[X_AXIS] || 
+       target[Y_AXIS] > 0 || target[Y_AXIS] < -settings.max_travel[Y_AXIS] || 
+       target[Z_AXIS] > 0 || target[Z_AXIS] < -settings.max_travel[Z_AXIS] ) {
+       
+    // 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.
+    if (sys.state == STATE_CYCLE) {
+      st_feed_hold();
+      while (sys.state == STATE_HOLD) {
+        protocol_execute_runtime();
+        if (sys.abort) { return; }
+      }
+    }
+    
+    mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
+    sys.execute |= EXEC_CRIT_EVENT; // Indicate soft limit critical event
+    protocol_execute_runtime(); // Execute to enter critical event loop and system abort
+  }
+}