[BUG] (steppers grinding, when dir pin through i2s, step pin through gpio)

[Ammar56788]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

Hello.

I have modified esp32 based controller board using i2s shiftregister...

I Config dir pin through i2s and step pin via esp32 main gpio(it seems support 40MHz)

But when i test, steppers just grinding and don't move any direction, I think step and dir pulse both are modulated for shiftregister at same time. Not for separate.

Why I do this?
Because I has issues with shiftregister frequency, that I see it isn't enough...

in circular motion, x and y are sin (t) or cos(t) and the they speed is they derivative equal cos and -sin. when we have constant 74hc595 frequency, so we have quantinized frequency for stepper motor, I mean frequency/n (because it don't have time between each update's cycle to send step pulse. maybe meant integer.) and when we have quantinized speed, we have quantinized sin and cos, meant stepstair waveform. Then when we got integral of that for calculating position of x y, we got some linear motion instead of smooth circular. So we have polygon. But I did a simulation with some code and I found frequency is enough to prevent from this effect. But that stepstair waveform for speed, cause something. Sudden changes in speed make problem. Because filament flow is smooth move but nozzle movement speed isnt smooth(accelerate). It's destroying any lin_adv :))

40mhz speed graph

250khz speed graph

Bug Timeline

No response

Expected behavior

I expected to Marlin and steppers work well when dir pin send through i2s and step pin through gpio

Actual behavior

Stepper just grinding

Steps to Reproduce

1.set dir pin in i2s pinout
2.set step pin in main gpio
3.configure and upload firmware
4.test steppers

Version of Marlin Firmware

2.1.2.4

Printer model

Esp32

Electronics

Did board. ramps1.5 with a4988

LCD/Controller

No lcd. Just Esp3d wifi

Other add-ons

74hc595 shiftregister

Bed Leveling

None

Your Slicer

Cura

Host Software

SD Card (headless)

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Configurations.zip

Additional information & file uploads

No response

[Ammar56788]

Related to #28054 .

[ellensp]

"I expected to Marlin and steppers work well when dir pin send through i2s and step pin through gpio"
this has never been a mode that anyone has implemented. there is simply no code to synchronize the two

[Ammar56788]

If just dir pins, heaters, fans, lcd, etc send via i2s, but step pins from gpio, you just has more free gpio and save steppers speed frequency high.

For some potential sync problem for direction change, can add a bit more waiting time before new step pwm, just after dir change, to make sure shiftregister was update dir pin status.