Merge pull request #4887 from thinkyhead/rc_autumn_fixups

Improve MINIMUM_STEPPER_PULSE

Marlin/Conditionals_post.h

@@ -708,4 +708,7 @@
     #define MAX_PROBE_Y (min(Y_MAX_POS, Y_MAX_POS + Y_PROBE_OFFSET_FROM_EXTRUDER))
   #endif
 
+  // Stepper pulse duration, in cycles
+  #define STEP_PULSE_CYCLES ((MINIMUM_STEPPER_PULSE) * CYCLES_PER_MICROSECOND)
+
 #endif // CONDITIONALS_POST_H

Marlin/macros.h

@@ -36,6 +36,9 @@
   #define CRITICAL_SECTION_END    SREG = _sreg;
 #endif
 
+// Clock speed factor
+#define CYCLES_PER_MICROSECOND (F_CPU / 1000000UL) // 16 or 20
+
 // Remove compiler warning on an unused variable
 #define UNUSED(x) (void) (x)
 

Marlin/stepper.cpp

@@ -460,8 +460,10 @@ void Stepper::isr() {
         _APPLY_STEP(AXIS)(_INVERT_STEP_PIN(AXIS),0); \
       }
 
+    #define CYCLES_EATEN_BY_CODE 240
+
     // If a minimum pulse time was specified get the CPU clock
-    #if MINIMUM_STEPPER_PULSE > 0
+    #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_CODE
       static uint32_t pulse_start;
       pulse_start = TCNT0;
     #endif
@@ -494,9 +496,8 @@ void Stepper::isr() {
     #endif // !ADVANCE && !LIN_ADVANCE
 
     // For a minimum pulse time wait before stopping pulses
-    #if MINIMUM_STEPPER_PULSE > 0
-      #define CYCLES_EATEN_BY_CODE 10
-      while ((uint32_t)(TCNT0 - pulse_start) < (MINIMUM_STEPPER_PULSE * (F_CPU / 1000000UL)) - CYCLES_EATEN_BY_CODE) { /* nada */ }
+    #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_CODE
+      while ((uint32_t)(TCNT0 - pulse_start) < STEP_PULSE_CYCLES - CYCLES_EATEN_BY_CODE) { /* nada */ }
     #endif
 
     #if HAS_X_STEP
@@ -688,10 +689,12 @@ void Stepper::isr() {
         E## INDEX ##_STEP_WRITE(INVERT_E_STEP_PIN); \
       }
 
+    #define CYCLES_EATEN_BY_E 60
+
     // Step all E steppers that have steps
     for (uint8_t i = 0; i < step_loops; i++) {
 
-      #if MINIMUM_STEPPER_PULSE > 0
+      #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_E
         static uint32_t pulse_start;
         pulse_start = TCNT0;
       #endif
@@ -708,9 +711,8 @@ void Stepper::isr() {
       #endif
 
       // For a minimum pulse time wait before stopping pulses
-      #if MINIMUM_STEPPER_PULSE > 0
-        #define CYCLES_EATEN_BY_E 10
-        while ((uint32_t)(TCNT0 - pulse_start) < (MINIMUM_STEPPER_PULSE * (F_CPU / 1000000UL)) - CYCLES_EATEN_BY_E) { /* nada */ }
+      #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_E
+        while ((uint32_t)(TCNT0 - pulse_start) < STEP_PULSE_CYCLES - CYCLES_EATEN_BY_E) { /* nada */ }
       #endif
 
       STOP_E_PULSE(0);