From feafc5e5abdc1acee8683411c83c4595885332f5 Mon Sep 17 00:00:00 2001
From: Yuri D'Elia <wavexx@thregr.org>
Date: Mon, 27 Jul 2020 19:12:56 +0200
Subject: [PATCH] Alternative schedule for LA ticks
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.
---
Firmware/stepper.cpp | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)
diff --git a/Firmware/stepper.cpp b/Firmware/stepper.cpp
index 949ffd58..8b21ee67 100644
--- a/Firmware/stepper.cpp
+++ b/Firmware/stepper.cpp
@@ -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;
}
}