yossi,
The IFI controllers are all based around interfacing with hobby servos and IFI H-Bridges that all take hobby servo pulse-train inputs, so the hardware as configured isn't going to be really useful for what you're attempting. If you're using the full-size IFI Robot Controller, then PWM outputs 13-16 are under direct control of the programmable user processor and are hooked directly into the PIC microprocessors CCP units. You can look in the PIC reference manual and datasheet on Kevin Watson's website to get info on how you could set these up to output a true 0-100% duty cycle PWM output. If you're using the Vex controller, PWM outputs 1-4 are arranged in a similar fashion. If you need more than 4 duty-cycle outputs, then your options are limited:
- Use the digital IOs combined with timers and really fast interrupt handlers to bootleg a duty-cycle generation output.
- Find or make a serial to duty-cycle PWM conversion board.
- Hack the IFI controller's Master hardware and firmware to force it to do what you want it to.
That last option is obviously the most difficult and most likely to totally hose your controller. I'm convinced it's technically possible to pull it off, but it would be very very difficult and it'd require a fairly extensive amount of code decompiling, reverse engineering, etc.