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Add some commentary to stepper ISR

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This commit is contained in:
Scott Lahteine 2016-08-30 14:21:15 -05:00
parent d9bcc7bb45
commit 4ec3d1ea58
1 changed files with 6 additions and 1 deletions
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7
Marlin/stepper.cpp
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@ -450,10 +450,12 @@ void Stepper::isr() {
#define _APPLY_STEP(AXIS) AXIS ##_APPLY_STEP
#define _INVERT_STEP_PIN(AXIS) INVERT_## AXIS ##_STEP_PIN
// Advance the Bresenham counter; start a pulse if the axis needs a step
#define PULSE_START(AXIS) \
_COUNTER(AXIS) += current_block->steps[_AXIS(AXIS)]; \
if (_COUNTER(AXIS) > 0) { _APPLY_STEP(AXIS)(!_INVERT_STEP_PIN(AXIS),0); }
// Stop an active pulse, reset the Bresenham counter, update the position
#define PULSE_STOP(AXIS) \
if (_COUNTER(AXIS) > 0) { \
_COUNTER(AXIS) -= current_block->step_event_count; \
@ -461,6 +463,7 @@ void Stepper::isr() {
_APPLY_STEP(AXIS)(_INVERT_STEP_PIN(AXIS),0); \
}
// If a minimum pulse time was specified get the CPU clock
#if MINIMUM_STEPPER_PULSE > 0
static uint32_t pulse_start;
pulse_start = TCNT0;
@ -476,6 +479,7 @@ void Stepper::isr() {
PULSE_START(Z);
#endif
// For non-advance use linear interpolation for E also
#if DISABLED(ADVANCE) && DISABLED(LIN_ADVANCE)
#if ENABLED(MIXING_EXTRUDER)
// Keep updating the single E axis
@ -492,6 +496,7 @@ void Stepper::isr() {
#endif
#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 */ }
@ -532,7 +537,7 @@ void Stepper::isr() {
}
#if ENABLED(ADVANCE) || ENABLED(LIN_ADVANCE)
// If we have esteps to execute, fire the next ISR "now"
// If we have esteps to execute, fire the next advance_isr "now"
if (e_steps[TOOL_E_INDEX]) OCR0A = TCNT0 + 2;
#endif