Post
by blmorris » Sat Sep 27, 2014 1:14 am
I'll look into this in some more depth later (posting from my phone now), but my initial guess is that PWM as implemented by the Servo class is different from the PWM needed by your DC motor controller. For the Servo class, the PWM signal indicates an angle for the servo to move to, there is a minimum and maximum pulse width but it is never zero. For a DC motor controller (guessing in this case, I'll look it up later) your speed is set by a duty cycle which can fully vary from 0 to 1. Duty cycle doesn't really have much meaning for a hobby servo control signal.
What you need to use is more likely the PWM function added recently to the Timer class by @dhylands, you can get it by updating the firmware on your pyboard.