Minor updates to code and commenting.

gcode.c

@@ -77,8 +77,9 @@ static float to_millimeters(float value)
 
 // Executes one line of 0-terminated G-Code. The line is assumed to contain only uppercase
 // characters and signed floating point values (no whitespace). Comments and block delete
-// characters have been removed. All units and positions are converted and exported to grbl's
+// characters have been removed. In this function, all units and positions are converted and 
-// internal functions in terms of (mm, mm/min) and absolute machine coordinates, respectively.
+// exported to grbl's internal functions in terms of (mm, mm/min) and absolute machine 
+// coordinates, respectively.
 uint8_t gc_execute_line(char *line) 
 {
 
@@ -203,7 +204,10 @@ uint8_t gc_execute_line(char *line)
   
   /* Pass 2: Parameters. All units converted according to current block commands. Position 
      parameters are converted and flagged to indicate a change. These can have multiple connotations
-     for different commands. Each will be converted to their proper value upon execution. */
+     for different commands. Each will be converted to their proper value upon execution. 
+     NOTE: Grbl unconventionally pre-converts these parameter values based on the block G and M 
+     commands. This is set out of the order of execution defined by NIST only for code efficiency/size 
+     purposes, but should not affect proper g-code execution. */ 
   float p = 0, r = 0;
   uint8_t l = 0;
   char_counter = 0;
@@ -242,10 +246,8 @@ uint8_t gc_execute_line(char *line)
   if (gc.status_code) { return(gc.status_code); }
   
   
-  /* Execute Commands: Perform by order of execution defined in NIST RS274-NGC.v3, Table 8, pg.41.
+  /* Execute Commands: Perform by order of execution defined in NIST RS274-NGC.v3, Table 8, pg.41. */
-     NOTE: Independent non-motion/settings parameters are set out of this order for code efficiency 
+    
-     and simplicity purposes, but this should not affect proper g-code execution. */
-  
   // ([F]: Set feed rate.)
     
   if (sys.state != STATE_CHECK_MODE) { 

limits.c

@@ -96,22 +96,16 @@ static void homing_cycle(uint8_t cycle_mask, int8_t pos_dir, bool invert_pin, fl
   // and speedy homing routine.
   // NOTE: For each axes enabled, the following calculations assume they physically move 
   // an equal distance over each time step until they hit a limit switch, aka dogleg.
-  uint32_t steps[N_AXIS];
+  uint32_t step_event_count, steps[N_AXIS];
-  uint8_t dist = 0;
+  uint8_t i, dist = 0;
   clear_vector(steps);
-  if (cycle_mask & (1<<X_AXIS)) { 
+  for (i=0; i<N_AXIS; i++) {
-    dist++;
+    if (cycle_mask & (1<<i)) { 
-    steps[X_AXIS] = lround(settings.steps_per_mm[X_AXIS]); 
+      dist++;
+      steps[i] = lround(settings.steps_per_mm[i]); 
+    }
   }
-  if (cycle_mask & (1<<Y_AXIS)) { 
+  step_event_count = max(steps[X_AXIS], max(steps[Y_AXIS], steps[Z_AXIS]));  
-    dist++;
-    steps[Y_AXIS] = lround(settings.steps_per_mm[Y_AXIS]); 
-  }
-  if (cycle_mask & (1<<Z_AXIS)) {
-    dist++;
-    steps[Z_AXIS] = lround(settings.steps_per_mm[Z_AXIS]);
-  }
-  uint32_t step_event_count = max(steps[X_AXIS], max(steps[Y_AXIS], steps[Z_AXIS]));  
   
   // To ensure global acceleration is not exceeded, reduce the governing axes nominal rate
   // by adjusting the actual axes distance traveled per step. This is the same procedure

motion_control.c

@@ -58,6 +58,10 @@ void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate)
   // backlash steps will need to be also tracked. Not sure what the best strategy is for this,
   // i.e. keep the planner independent and do the computations in the status reporting, or let
   // the planner handle the position corrections. The latter may get complicated.
+  // TODO: Backlash comp positioning values may need to be kept at a system level, i.e. tracking 
+  // true position after a feed hold in the middle of a backlash move. The difficulty is in making 
+  // sure that the stepper subsystem and planner are working in sync, and the status report 
+  // position also takes this into account.
 
   // If the buffer is full: good! That means we are well ahead of the robot. 
   // Remain in this loop until there is room in the buffer.
@@ -229,8 +233,11 @@ void mc_go_home()
   float pulloff_target[N_AXIS];
   clear_vector_float(pulloff_target); // Zero pulloff target.
   clear_vector_long(sys.position); // Zero current position for now.
+  uint8_t dir_mask[N_AXIS];
+  dir_mask[X_AXIS] = (1<<X_DIRECTION_BIT);
+  dir_mask[Y_AXIS] = (1<<Y_DIRECTION_BIT);
+  dir_mask[Z_AXIS] = (1<<Z_DIRECTION_BIT);
   uint8_t i;
-  uint8_t dir_mask[N_AXIS] = { bit(X_DIRECTION_BIT),bit(Y_DIRECTION_BIT),bit(Z_DIRECTION_BIT) };
   for (i=0; i<N_AXIS; i++) {
     // Set up pull off targets and machine positions for limit switches homed in the negative
     // direction, rather than the traditional positive. Leave non-homed positions as zero and
@@ -266,8 +273,8 @@ void mc_go_home()
 // operation of cycle start is manually issuing a cycle start command whenever the user is
 // ready and there is a valid motion command in the planner queue.
 // NOTE: This function is called from the main loop and mc_line() only and executes when one of
-// two conditions exist respectively: There are no more blocks sent (i.e. streaming is finished),
+// two conditions exist respectively: There are no more blocks sent (i.e. streaming is finished, 
-// or the planner buffer is full and ready to go.
+// single commands), or the planner buffer is full and ready to go.
 void mc_auto_cycle_start() { if (sys.auto_start) { st_cycle_start(); } }
 
 

stepper.c

@@ -2,7 +2,7 @@
   stepper.c - stepper motor driver: executes motion plans using stepper motors
   Part of Grbl
 
-  Copyright (c) 2011-2012 Sungeun K. Jeon
+  Copyright (c) 2011-2013 Sungeun K. Jeon
   Copyright (c) 2009-2011 Simen Svale Skogsrud
   
   Grbl is free software: you can redistribute it and/or modify
@@ -107,6 +107,7 @@ void st_go_idle()
   // Disable stepper driver interrupt. Allow Timer0 to finish. It will disable itself.
   TIMSK2 &= ~(1<<OCIE2A); // Disable Timer2 interrupt
   TCCR2B = 0; // Disable Timer2
+  busy = false;
 
   // Disable steppers only upon system alarm activated or by user setting to not be kept enabled.
   if ((settings.stepper_idle_lock_time != 0xff) || bit_istrue(sys.execute,EXEC_ALARM)) {
@@ -193,7 +194,6 @@ ISR(TIMER2_COMPA_vect)
     } else {
       st_go_idle();
       bit_true(sys.execute,EXEC_CYCLE_STOP); // Flag main program for cycle end
-      busy = false;
       return; // Nothing to do but exit.
     }  
   } 
@@ -237,7 +237,6 @@ ISR(TIMER2_COMPA_vect)
       if (st.delta_d <= current_block->rate_delta) {
         st_go_idle();
         bit_true(sys.execute,EXEC_CYCLE_STOP);
-        busy = false;
         return;
       }
     }
@@ -330,7 +329,7 @@ void st_init()
   TCNT2 = 0; // Clear Timer2 counter
   TCCR2A = (1<<WGM21);  // Set CTC mode
   OCR2A = (F_CPU/ISR_TICKS_PER_SECOND)/8 - 1; // Set Timer2 CTC rate
-  
+
   // Configure Timer 0
   TIMSK0 &= ~(1<<TOIE0);
   TCCR0A = 0; // Normal operation