Hard limits, homing direction, pull-off limits after homing, status reports in mm or inches, system alarm, and more.

- Thank you statement added for Alden Hart of Synthetos.

- Hard limits option added, which also works with homing by pulling off
the switches to help prevent unintended triggering. Hard limits use a
interrupt to sense a falling edge pin change and immediately go into
alarm mode, which stops everything and forces the user to issue a reset
(Ctrl-x) or reboot.

- Auto cycle start now a configuration option.

- Alarm mode: A new method to kill all Grbl processes in the event of
something catastrophic or potentially catastropic. Just works with hard
limits for now, but will be expanded to include g-code errors (most
likely) and other events.

- Updated status reports to be configurable in inches or mm mode. Much
more to do here, but this is the first step.

- New settings: auto cycle start, hard limit enable, homing direction
mask (which works the same as the stepper mask), homing pulloff
distance (or distance traveled from homed machine zero to prevent
accidental limit trip).

- Minor memory liberation and calculation speed ups.

protocol.c

@@ -73,7 +73,7 @@ void protocol_status_report()
  // may be distance to go on block, processed block id, and feed rate. A secondary, non-critical
  // status report may include g-code state, i.e. inch mode, plane mode, absolute mode, etc. 
  //   The report generated must be as short as possible, yet still provide the user easily readable
- // information, i.e. 'x0.23,y120.4,z2.4'. This is necessary as it minimizes the computational 
+ // information, i.e. '[0.23,120.4,2.4]'. This is necessary as it minimizes the computational 
  // overhead and allows grbl to keep running smoothly, especially with g-code programs with fast, 
  // short line segments and interface setups that require real-time status reports (5-20Hz).
 
@@ -85,24 +85,33 @@ void protocol_status_report()
  // home position by the user (likely through '$' setting interface).
  // Successfully tested at a query rate of 10-20Hz while running a gauntlet of programs at various 
  // speeds.
- int32_t print_position[3];
- memcpy(print_position,sys.position,sizeof(sys.position));
- #if REPORT_INCH_MODE
-   printString("MPos:["); printFloat(print_position[X_AXIS]/(settings.steps_per_mm[X_AXIS]*MM_PER_INCH));
-   printString(","); printFloat(print_position[Y_AXIS]/(settings.steps_per_mm[Y_AXIS]*MM_PER_INCH));
-   printString(","); printFloat(print_position[Z_AXIS]/(settings.steps_per_mm[Z_AXIS]*MM_PER_INCH));
-   printString("],WPos:["); printFloat((print_position[X_AXIS]/settings.steps_per_mm[X_AXIS]-sys.coord_system[sys.coord_select][X_AXIS]-sys.coord_offset[X_AXIS])/MM_PER_INCH);
-   printString(","); printFloat((print_position[Y_AXIS]/settings.steps_per_mm[Y_AXIS]-sys.coord_system[sys.coord_select][Y_AXIS]-sys.coord_offset[Y_AXIS])/MM_PER_INCH);
-   printString(","); printFloat((print_position[Z_AXIS]/settings.steps_per_mm[Z_AXIS]-sys.coord_system[sys.coord_select][Z_AXIS]-sys.coord_offset[Z_AXIS])/MM_PER_INCH);
- #else
-   printString("MPos:["); printFloat(print_position[X_AXIS]/(settings.steps_per_mm[X_AXIS]));
-   printString(","); printFloat(print_position[Y_AXIS]/(settings.steps_per_mm[Y_AXIS]));
-   printString(","); printFloat(print_position[Z_AXIS]/(settings.steps_per_mm[Z_AXIS]));
-   printString("],WPos:["); printFloat(print_position[X_AXIS]/settings.steps_per_mm[X_AXIS]-sys.coord_system[sys.coord_select][X_AXIS]-sys.coord_offset[X_AXIS]);
-   printString(","); printFloat(print_position[Y_AXIS]/settings.steps_per_mm[Y_AXIS]-sys.coord_system[sys.coord_select][Y_AXIS]-sys.coord_offset[Y_AXIS]);
-   printString(","); printFloat(print_position[Z_AXIS]/settings.steps_per_mm[Z_AXIS]-sys.coord_system[sys.coord_select][Z_AXIS]-sys.coord_offset[Z_AXIS]);
- #endif
- printString("]\r\n");
+ uint8_t i;
+ int32_t current_position[3]; // Copy current state of the system position variable
+ memcpy(current_position,sys.position,sizeof(sys.position));
+ float print_position[3];
+
+ // Report machine position
+ printPgmString(PSTR("MPos:[")); 
+ for (i=0; i<= 2; i++) {
+   print_position[i] = current_position[i]/settings.steps_per_mm[i];
+   if (bit_istrue(settings.flags,BITFLAG_REPORT_INCHES)) { print_position[i] *= INCH_PER_MM; }
+   printFloat(print_position[i]);
+   if (i < 2) { printPgmString(PSTR(",")); }
+ }
+ 
+ // Report work position
+ printPgmString(PSTR("],WPos:[")); 
+ for (i=0; i<= 2; i++) {
+   if (bit_istrue(settings.flags,BITFLAG_REPORT_INCHES)) {
+     print_position[i] -= (sys.coord_system[sys.coord_select][i]+sys.coord_offset[i])*INCH_PER_MM;
+   } else {
+     print_position[i] -= sys.coord_system[sys.coord_select][i]+sys.coord_offset[i];
+   }
+   printFloat(print_position[i]);
+   if (i < 2) { printPgmString(PSTR(",")); }
+ }
+   
+ printPgmString(PSTR("]\r\n"));
 }
 
 
@@ -129,6 +138,12 @@ void protocol_execute_runtime()
 {
   if (sys.execute) { // Enter only if any bit flag is true
     uint8_t rt_exec = sys.execute; // Avoid calling volatile multiple times
+    
+    // System alarm. Something has gone wrong. Disable everything until system reset.
+    if (rt_exec & EXEC_ALARM) {
+      while (bit_isfalse(sys.execute,EXEC_RESET)) { sleep_mode(); }
+      bit_false(sys.execute,EXEC_ALARM);
+    } 
   
     // System abort. Steppers have already been force stopped.
     if (rt_exec & EXEC_RESET) {
@@ -157,12 +172,12 @@ void protocol_execute_runtime()
     
     if (rt_exec & EXEC_CYCLE_START) { 
       st_cycle_start(); // Issue cycle start command to stepper subsystem
-      #ifdef CYCLE_AUTO_START
+      if (bit_istrue(settings.flags,BITFLAG_AUTO_START)) {
         sys.auto_start = true; // Re-enable auto start after feed hold.
-      #endif
+      }
       bit_false(sys.execute,EXEC_CYCLE_START);
-    } 
-  }
+    }
+  }  
 }