We use the small circuit linked below to generate motor controller PWM signals. At the moment it works with Talons and Victors. The timing would need a tweak to run a Jaguar.
The potentiometer is mounted on a joystick with a spring return to center. We like that arrangement because the motor always returns to OFF when the stick is released.
The code is in PIC assembler and anyone who wants it can have it.
https://docs.google.com/file/d/0B6MH...it?usp=sharing