during our 2017 season, our lights on our PDP never turned solid green like other teams. we ran 2 TalonSRX’s over the canbus, and they worked fine, and never had an issue. We are getting ready to redo the wiring on our old bot this weekend, and want to do it correctly to achieve those green lights!! What is the correct order to daisychain the canbus components in?
You can see the meaning of the status lights by going here.
The issue (which may not be an issue currently) is that at one point your PDP had a fault and recorded it, the lights will be yellow until you clear the sticky faults. You can do this by going to the RoboRIO Web Dashboard (hook up to your RoboRIO by ethernet or USB and point your web browser to roborio-3577-frc.local), selecting your PDP, click self-test to see the status of your PDP (this will help you evaluate if there is currently an issue), double click self-test to clear the sticky faults.
If you have any questions or need further help (or are concerned your CAN wiring is still not optimal) post again or send me a PM.
There is no correct order, except that the ends must have terminating resistors. The RIO has a resistor, so it should be at one end of the bus (it only has one pair of connectors, so that’s unusual to mess up).
The PDP also has a terminating resistor which may be enabled or disabled through a jumper. The easiest way to correctly terminate the other end is to move that jumper inboard, towards the status lights, and have the PDP be “last” in your chain.
If you want to put the PDP in the middle of your chain, move the jumper outboard and put a 120 ohm resistor at the end of the chain away from the RIO.
Can you post an image of that jumper and where it needs to be to use the PDP as an endpoint?
Here’s an example of the PDP CAN termination jumper set ON to act as an endpoint:
The PDP User’s Guide has a photo on page 13.
Would the order change at all if I added a PCM into the mix? Could I still use the pdp as the endpoint?
The PCM is a regular CAN device and can go anywhere on the bus between the terminating resistors. Because it has weidmuller connectors, it’s a great efficiency to put it between two motor controllers.