3DPrinting/Prusa-Firmware
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Alternative schedule for LA ticks

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Remove most of the original complexity from advance_spread.

Instead of accumulating time to be scheduled, plan ahead of time each
eISR tick using the next main interval + an accumulator (eISR_Err),
which keeps everything much simpler.

The distribution of the advance ticks is now using the real LA
frequency, which leaves a bit more time between the last LA tick and
the main stepper isr.

We take advantage of the accumulator to force a LA tick right after the
first main tick, which removes a +/- 1 scheduling error at higher step
rates.

When decompressing, we force 2 steps instead, so that the direction
reversal happens immediately (first tick zeros esteps, second inverts
the sign), removing another +/- 1 error at higher step rates.
This commit is contained in:
Yuri D'Elia 2020-07-27 19:12:56 +02:00
parent a08ca19ade
commit feafc5e5ab
1 changed files with 16 additions and 23 deletions
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39
Firmware/stepper.cpp
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@ -125,7 +125,7 @@ volatile signed char count_direction[NUM_AXIS] = { 1, 1, 1, 1};
static uint16_t main_Rate;
static uint16_t eISR_Rate;
static uint16_t eISR_Err;
static uint32_t eISR_Err;
static uint16_t current_adv_steps;
static uint16_t target_adv_steps;
@ -733,38 +733,30 @@ FORCE_INLINE uint16_t fastdiv(uint16_t q, uint8_t d)
FORCE_INLINE void advance_spread(uint16_t timer)
{
if(eISR_Err > timer)
eISR_Err += timer;
uint8_t ticks = 0;
while(eISR_Err >= current_block->advance_rate)
{
++ticks;
eISR_Err -= current_block->advance_rate;
}
if(!ticks)
{
// advance-step skipped
eISR_Err -= timer;
eISR_Rate = timer;
nextAdvanceISR = timer;
return;
}
// at least one step
uint8_t ticks = 1;
uint32_t block = current_block->advance_rate;
uint16_t max_t = timer - eISR_Err;
while (block < max_t)
{
++ticks;
block += current_block->advance_rate;
}
if (block > timer)
eISR_Err += block - timer;
else
eISR_Err -= timer - block;
if (ticks <= 4)
eISR_Rate = fastdiv(timer, ticks);
if (ticks <= 3)
eISR_Rate = fastdiv(timer, ticks + 1);
else
{
// >4 ticks are still possible on slow moves
eISR_Rate = timer / ticks;
eISR_Rate = timer / (ticks + 1);
}
nextAdvanceISR = eISR_Rate / 2;
nextAdvanceISR = eISR_Rate;
}
#endif
@ -876,11 +868,12 @@ FORCE_INLINE void isr() {
}
else {
// reset error and iterations per loop for this phase
eISR_Err = current_block->advance_rate / 4;
eISR_Err = current_block->advance_rate;
e_step_loops = current_block->advance_step_loops;
if ((la_state & ADV_ACC_VARY) && e_extruding && (current_adv_steps > target_adv_steps)) {
// LA could reverse the direction of extrusion in this phase
eISR_Err += current_block->advance_rate;
LA_phase = 0;
}
}