[Grbl_Esp32 Issue#1] Step pulse off timing

#1 – buildlog 于 2018-07-24

The solution mentioned above appears to work fine.

I removed the timer interrupt that turns off the step pulse and replaced it with a delay loop at the end of the main stepper driver interrupt (void IRAM_ATTR onStepperDriverTimer())

> // wait for step pulse time to complete…some of it should have expired during code above
> while (esptimergettime() < steppulseofftime)
> {
> NOP(); // spin here until time to turn off step
> }
> setstepperpins_on(0); // turn all off
>

The stock Grbl setting is 3 uSecs, which is also the minimum. I am not sure why that is a minimum, but I’ll leave it. Common drivers like the TI DRV8825 require a step pulse length of 1.9uS.

I don’t think it should impact performance because the time is so brief. You can’t go any faster than what the minimum step pulse timing will allow anyways. I have not profiled the code before that, but it probably uses up much of the time.

I have not committed the code yet, in case anyone wants to comment on this.

#2 – buildlog 于 2018-07-24

For reference, here is the DRV8825 timing diagram.

!image

#3 – ggallant571 于 2018-07-26

I have been doing my own gcode processor for a couple of years using a STM32 device. Recently have started using various ESP devices for remote sensing projects. More than willing to migrate to your implementation.

#4 – buildlog 于 2018-07-26

Changed to use method described above.