Cheaper Alternative to Tallon

[bharrison6]

Is there any pwm or CAN operated motor controllers that are cheaper to buy than what is normally used for FRC. Reason I am asking.

I am a teacher implementing a Robotics class. I have almost 0 funds. My team is a team ran by two high schools with again almost 0 funds. We only have two roborio's so this is the plan for our class.

Raspberry Pi2 Model B has some pretty impressive features. I am looking into how I might produce pwm signals from them to run motor controllers or possibly a CAN signal. They cost ~$35 each.

For motor controllers I found.
http://www.ebay.com/itm/like/2013367...lpid=82&chn=ps
These use PWM but I don't believe they will work like a talon because they are speed "forward" only. There are some that have a reverse switch which could possibly be programmed to automatically switch when you need to reverse but I think half the PWM being used for forward and half for reverse like FRC motor controllers would be easier. Any alternatives in that $15 range?