Minimum PWM Frequency

[amaury10]

Hello everyone,

I'm building a CNC Foam Cutter machine based on SKR Pico board.
I wonder what is the minimum PWM Frequency for spindle, because I'd like to have around 1Hz (it drives an SSR that supply the hot wire).

When I put 1 in $33 I have really strange behaviours. Is there a minimum limit or is there a bug in the PWM generation ?

Cheers,

Amaury.

[terjeio]

There is a minimum limit dictated by the MCU clock, max prescaler value and PWM timer resolution.
The current algorithm for selecting the prescaler value is rather crude and I may change that to increase the range. I recently started looking into that for another project so may port that over to the grblHAL driver soon.

[amaury10]

Ok, do you think possible to reach down to 1Hz ?

[terjeio]

It seems ~10Hz is the lowest possible.

[amaury10]

More than enough for solid state relays :-)

[terjeio]

New version with a fix for this was committed a while back.