Hi Roger, I think I know what you are refering to as I have seen cuircuits that use a Pic for the clock frequency, but this circuit definetly uses the Pic to change the Vref.

Ok so no luck finding the code for the pic, plently of references to its theoretical use but no specifics. There are plenty using the 555 timer circuits tho.

The closest I can find is the Rotary table drive that kwackers posted. apparently it was designed to drive an L297 setup and provide a holding current using PWM on the Vref pin. The only problem is I cant open the hex and wouldnt know what to look for any way. Maybe I will have to ask him direct for help :whistling:.

Ive also found conformation that this circuit was never built or tested so Im inclined to leave out the Short-circuit protection for the motor wires to keep it simple. may be I could look at it later and just use a known design to get the mill working?