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Optimize timer multiplexing and increase stepTimerQuantum 

Avoid calling PulseGen::Step() on idle axes by checking for a non-zero
queue size (which is more efficient to compute).

Increase stepTimerQuantum to 128us to ensure acceleration can be
computed in realtime for 3 axes at the same time.

Fix the logic of the static assertion, which was flipped: we need to
create slices larger than the maximal step frequency in order to ensure
no axis is starved while moving.
pull/108/head
Yuri D'Elia 2021-08-28 18:13:33 +02:00 committed by DRracer
parent d23ed53f3c
commit 9c3b31756e
3 changed files with 13 additions and 8 deletions
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7
src/config/config.h
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@ -68,9 +68,10 @@ static constexpr uint8_t blockBufferSize = 2;
/// Step timer frequency divider (F = F_CPU / divider) /// Step timer frequency divider (F = F_CPU / divider)
static constexpr uint8_t stepTimerFrequencyDivider = 8; static constexpr uint8_t stepTimerFrequencyDivider = 8;
/// Smallest stepping ISR scheduling slice (T = F_CPU / divider * quantum) /// Smallest stepping ISR scheduling slice (T = 1 / (F_CPU / divider) * quantum)
/// 16 = 8us (25us is the max frequency interval per maxStepFrequency) /// 25us is the max frequency interval per maxStepFrequency attainable for a single axis
static constexpr uint8_t stepTimerQuantum = 16; /// while accelerating: with 3 axes this yields a required minimum of 75us
static constexpr uint16_t stepTimerQuantum = 256; // 256 = 128us
/// Pulley axis configuration /// Pulley axis configuration
static constexpr AxisConfig pulley = { static constexpr AxisConfig pulley = {

10
src/modules/motion.cpp
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@ -74,10 +74,14 @@ st_timer_t Motion::Step() {
for (uint8_t i = 0; i != NUM_AXIS; ++i) { for (uint8_t i = 0; i != NUM_AXIS; ++i) {
timers[i] = axisData[i].residual; timers[i] = axisData[i].residual;
if (timers[i] <= config::stepTimerQuantum) { if (timers[i] <= config::stepTimerQuantum) {
timers[i] += axisData[i].ctrl.Step(axisParams[i].params); if (timers[i] || !axisData[i].ctrl.QueueEmpty()) {
if (st_timer_t next = axisData[i].ctrl.Step(axisParams[i].params)) {
timers[i] += next;
// axis has been moved, run the tmc2130 Isr for this axis // axis has been moved, run the tmc2130 Isr for this axis
axisData[i].drv.Isr(axisParams[i].params); axisData[i].drv.Isr(axisParams[i].params);
}
}
} }
} }

4
src/modules/motion.h
View File

@ -18,8 +18,8 @@ using pulse_gen::st_timer_t;
// Check for configuration invariants // Check for configuration invariants
static_assert( static_assert(
(1. / (F_CPU / config::stepTimerFrequencyDivider) * config::stepTimerQuantum) (1. / (F_CPU / config::stepTimerFrequencyDivider) * config::stepTimerQuantum)
< (1. / config::maxStepFrequency / 2), > (1. / config::maxStepFrequency),
"stepTimerQuantum must be smaller than the maximal stepping frequency interval"); "stepTimerQuantum must be larger than the maximal stepping frequency interval");
/// Main axis enumeration /// Main axis enumeration
struct AxisParams { struct AxisParams {