> The frequency really doesn't matter.

Um, I bet .1Hz or 1MHz wouldn't work too well.

> It gets smoothed out by an RC filter anyway.

Huh!!?  Unless you're talking about linear drive (and we were specifically
talking about PWM drive) there is no RC filter.  The pulses get smoothed out
by the inertia of the motor, and to some extent by the motor coils acting as
inductors.

> If you are using the CCP module from a PIC I would run it at least
> at 1500 cycles/sec at a  50% duty cycle.  I think the minimum frequency
you
> can run with a 20mHz resonator is about 1230 cycles/sec.

The 1230Hz figure sounds about right from memory, and should be fine for
driving a motor.  The only drawback at that frequency might be an annoying
audible whine.  At a few 100Hz PWM frequency you can do it in software and
therefore drive a bunch of motors from the same PIC.


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