[Joe Johnson]

Concerning alternatives to CAN:

My experience (limited I know) is that I2C and SPI can work just fine with reasonable jumps to piggy back boards. We may have to slow down the clock speeds, but we are still lightyears ahead of the current situation.

Concerning 1 wire failure vs. the current 16 PWM wires:
I know which failure I would choose. With 1 wire on a serial wire at least you get feedback if a Victor goes dark. There are a lot of times when we don't know if the Victor died, or the PWM cable unplugged or the motor lead came undone. It would be a relatively simple matter to set up a dashboard program tell you "lost Victor N" rather than having to go to each Victor to look for for a solid orange LED. Also, with only one connector to the RC you may actually be able to have a connector housing that ensures good connections and perhaps even a positive locking feature.

As doing absolute position feedback with the back EMF method:
I think that end of travel switches can help calibrate the integration. Also, even without such as sync switch, this is no different then having quardrature decode on our wheels. Without a "zero" point, you can't control to absolute position. While I am on the topic, the folks on Charmed Labs claim that the drift from the integration of velocity to position is on the order of what they see from wheel slip when they use encoders. I don't know if I believe them but at least that is their claim.

As to the speed of the motors that they are controlling:
I am more impressed that they can make it go slow to be honest. From a controls point of view, I think the signal to noise problem is worse making an ungeared or lightly geared motor go slow that going fast. There are limitations to be sure. The limit on the duty cycle of the motor is definitely going to cause problems in some applications as will drift, parameter tuning etc. But on balance, I think that there may be something worth exploring for future FIRST robotic applications.

Good discussion in any case.

Joe J.