$33= Not recognised by my board

Hi There! :slight_smile:
I have a new control board, it’s a Woodpecker. GRBL 1.1f. They are used on the Sain Smart Mini CNC 3018 PRO. I’m waiting for a new laser driver to come in the mail, but in the mean time I want to set the PWM frequency on the woodpecker board. This one here.



When I try to input the required 1000 Hz for the driver $33=1000, I get
33=1000 error:3 Grbl '’ system command was not recognized or supported.”
the new driver states it uses 1KHz setting.

I have been moving the steppers around and setting up speeds, limits, steps per… with no problem.
I read somewhere on the net that there is a file, H something that may contain the PWM frequency settings, but don’t know how to get the file.

Here are the settings $$




































[HLP:$$ $# $G $I $N $x=val $Nx=line $J=line $SLP $C $X $H ~ ! ? ctrl-x]


That board is using the old ATMega328P processor that probably doesn’t have a lot of flexibility (like none) in the PWM rate. You get what you get…

It may be true that there are adjustments possible if you rebuild the firmware, ie, modify an ‘.h’ file, but that’s a puddle much deeper than tweaking some parameters.

Hi Tom thanks for the quick reply!
So then there is no way to know what the PWM freq is for this board?


Well, if the spec says 1000Hz, then maybe it is. You just can’t change it, whatever it is. One way to tell, if you have an oscilloscope, is to set the PWM to 50% and look at the frequency coming out the pin.

There are plenty of cheap USB oscilloscopes around (I think I’ve seen less than $30USD) if you think you can use it elsewhere.

The laser driver board runs at 1000Hz. I don’t know what the Woodpecker controller puts out.

I have a proper traditional digital scope.


Just noted from the manual, that the woodpecker controler indeed does has a
Atmel ATMEGA328P on it.


Well it looks like I got lucky!!
the scope shows a PWM freq. of 977.317 Hz, close enough for me!!!

Thanks Tom for suggesting the scope, haven’t used it in a couple of years :frowning:


Close enough for your laser too, I imagine… :wink:

1 Like

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.