[Kevin Sevcik]

Originally Posted by dmelcer9

Recently, our team wired up a board with a few talon SRX's (using CAN) to test a few encoders, though they aren't working exactly right. I tried a few different configurations of motor controllers and recorded the results:

RoboRIO - PDP: PDP light is red, doesn't connect

RoboRIO- Motor Controller A - PDP: MCA light alternates red, PDP light is orange, and the PDP shows up in the web based config

RoboRIO- MCB - PDP: MCB works, PDP light is red and doesn't show up in config

RoboRIO- MCB(CAN wiring reversed) - PDP: MCB alternates orange and PDP flashes orange, but neither show up in the web config

RIO-MCA-MCB(original CAN wiring)-PDP: MCB works and shows up, MCA alternates red and PDP flashes red (neither show up).

RIO-MCA-MCB(reversed CAN)-PDP: MCB and the PDP both work, though MCA still alternates red.

RIO-MCB(original CAN) - MCA - PDP: both MCB and PDP are orange, but neither show up in config; MCA is red.

RIO-MCB(reversed) - MCA - PDP: both MCB and PDP work, MCA is red.

Even though it shouldn't matter what direction the CAN wiring is in, it somehow does. Also, MCB and the PDP shouldn't be affected by MCA (but of course they are). Additionally, order shouldn't matter, but it affects the motor controllers.

What exactly do you mean it shouldn't matter what direction the can wiring is in? If you mean it doesn't matter if you connect green-green and yellow-yellow, I'm pretty sure you're wrong.

Anyways, direct connection from the RoboRIO to the PDP really should work. Maybe you have a bad termination resistor. Power everything off and disconnect everything, and do a resistance check between green-yellow on the RoboRIO and the PDP. You should get 120 ohms in both locations.