Simplify setting of STATE_CYCLE and ISR interval.

Set sys.state to STATE_CYCLE directly instead of calling back to
st_wakeup().

Convert get_step_time() to a constant and rename it to ISR_INTERVAL.

sim/simulator.c

@@ -29,6 +29,11 @@
 #include "../nuts_bolts.h"
 #include "simulator.h"
 
+// Derived from OCR2A set during stepper init. Not simplified because
+// OCR2A formula results in an unsigned int, which results in a slightly
+// different value than simplifying to 1 / ISR_TICKS_PER_SECOND.
+#define ISR_INTERVAL ((F_CPU/ISR_TICKS_PER_SECOND)/8) * 8.0 / F_CPU
+
 // This variable is needed to determine if execute_runtime() is called in a loop
 // waiting for the buffer to empty, as in plan_synchronize()
 // it is reset in serial_write() because this is certainly called at the end of
@@ -85,13 +90,15 @@ void sim_stepper() {
   // to let it handle sys.cycle_start etc.
   if(current_block==NULL) {
 	  interrupt_TIMER2_COMPA_vect();
-      sim_time+= get_step_time();
+      sim_time+= ISR_INTERVAL;
 	  return;
   }
 
+  sys.state = STATE_CYCLE;
+
   while(current_block==plan_get_current_block()) {
     interrupt_TIMER2_COMPA_vect();
-    sim_time+= get_step_time();
+    sim_time+= ISR_INTERVAL;
 
     // Check to see if we should print some info
     if(step_time>0.0) {
@@ -108,6 +115,7 @@ void sim_stepper() {
     }
 
   }
+
   // always print stepper values at the end of a block
   if(step_time>0.0) {
 	fprintf(step_out_file, "%20.15f, %d, %d, %d\n", sim_time, sys.position[X_AXIS], sys.position[Y_AXIS], sys.position[Z_AXIS]);
@@ -171,12 +179,6 @@ void printBlock() {
 // Only when plan_synchronize() wait for the whole buffer to clear, the stepper interrupt
 // to finish all pending moves.
 void handle_buffer() {
-  if (plan_check_full_buffer() && sys.state != STATE_CYCLE) {
-    // Autostart the cycle, and call st_wake_up()
-    sys.state = STATE_CYCLE;
-    st_wake_up();
-  }
-
   // runtime_second_call is reset by serial_write() after every command.
   // Only when execute_runtime() is called repeatedly by plan_synchronize()
   // runtime_second_call will be incremented above 2
@@ -189,37 +191,3 @@ void handle_buffer() {
   }
 }
 
-double get_step_time() {
-/* code for the old stepper algorithm
-  uint16_t ceiling;
-  uint16_t prescaler;
-  uint32_t actual_cycles;
-  uint8_t invalid_prescaler= 0;
-
-  prescaler= ((TCCR1B>>CS10) & 0x07) - 1;
-  ceiling= OCR1A;
-
-  switch(prescaler) {
-    case 0:
-      actual_cycles= ceiling;
-	  break;
-    case 1:
-      actual_cycles= ceiling * 8L;
-	  break;
-    case 2:
-      actual_cycles = ceiling * 64L;
-	  break;
-    case 3:
-      actual_cycles = ceiling * 256L;
-	  break;
-    case 4:
-      actual_cycles = ceiling * 1024L;
-	  break;
-    default:
-    	invalid_prescaler= 1;
-  }
-
-  if(invalid_prescaler) return 12345.0;
-  else return (double)actual_cycles/F_CPU;*/
-  return (double)((ocr2a+1)*8)/(double)(F_CPU);
-}

sim/simulator.h

@@ -51,10 +51,4 @@ void handle_buffer();
 // Print information about the most recently inserted block
 void printBlock();
 
-// Calculate the time between stepper interrupt calls from TCCR1B and OCR1A AVR registers
-// which are set in config_step_timer in stepper.c
-// This reconstructs the stepper-internal value of variable st.cycles_per_step_event
-// The reconstruction is done to truely decouple the simulator from the actual grbl code
-double get_step_time();
-
 #endif