ESP32-S3: Speed Isn't Updated Until Next Motor Step

[DominicChm]

If you change motor speed during a runForward or runBackward move on an ESP32-S3, the motor won't begin ramping to the next speed until the next step of the currently applied speed.

This is a problem when changing from very slow to very fast speeds, where a single motor step could take ~10s. In the attached example, there's a ~10s delay before the motor starts moving at the desired 500 steps/sec. I'd expect it to start moving at 500 steps/sec basically instantly.

#include <Arduino.h>
#include "FastAccelStepper.h"

#define PIN_M1_EN 4
#define PIN_M1_STP 17
#define PIN_M1_DIR 18

FastAccelStepperEngine engine = FastAccelStepperEngine();
FastAccelStepper *x = NULL;

void setup() {
    Serial.begin(115200);
    engine.init();
    x = engine.stepperConnectToPin(PIN_M1_STP, FasDriver::RMT);
    if (x)
    {
        x->setDirectionPin(PIN_M1_DIR);
        x->setEnablePin(PIN_M1_EN);
        x->setAutoEnable(true);

        x->enableOutputs();
        x->setSpeedInHz(500);    // 500 steps/s
        x->setAcceleration(500);
    }
    Serial.println("Starting...\n");
    x->setSpeedInMilliHz(100);
    x->runForward();
    delay(10);
    x->setSpeedInHz(500);
    x->runForward();
}

void loop() {}

[gin66]

if I understand you correctly, then the current behavior is not what you expect. The driver was requested to run forward with 100 mHz. This means one step per 10s. So it will immediately issue the step and make a 10s pause. Now the app is waiting 10s too. Most likely the driver will just have issued the second step - and as requested make it at 100mHz, so a 10s pause will be done again. The issue is, that this pause will be executed unconditionally - so that the driver is fulfilling the 100mHz request. It can only be interrupted by forceStopAndNewPosition().

This concept is already existing since years and apparently you are the first one, who encounters it. Short term solutions: perform forceStopAndNewPosition() or use moveTimed() or use forwardStep().

Changing the ramp generator to your expectation is not straightforward. All pauses are non-interruptible, but just short enough that no one will notice. That‘s why, several years ago I left it like this - with the uninterruptible pause. From philosophical perspective, the current behavior can be argued to be reasonable….