Our team is having a problem with our CAN bus that we do not know how to solve. Our talons, victors, PCM and PDP are all blinking red indicating that the CAN bus is not being seen. Our CAN setup is rio→ victor→ victor→ talon→ pcm→ talon x7→ PDP.
When we turn the robot on, for a split second, the Talon lights blink orange and the PDP and PCM blink green. However, after a split second, the talons start blinking red and the PDP and PCM start to flash red. When we unplugged the CAN connection that went from the first talon to the PCM, the lights on the talons that were past the PCM were blinking orange in normal fashion as if showing that CAN could be seen. However, the first talon, victors, and the PCM were blinking red. Lastly, when we connected USB-B to rio to see phoenix tuner, we could not see any CAN devices.
We went through a series of steps to try and debug the problem.
- The first thing we did was we bypassed the PCM and tried to connect the two CAN wires that would normally go into the PCM together. We did this because we originally thought that the PCM was the problem because of the strange light behavior when we unplugged CAN. However, this did not solve the problem.
- We also tested for continuity on the green wire and the yellow wire starting from the wire that would go in the Rio to the wire that terminates in the PDP. We did this by using a multimeter and connecting the green wire that goes into the Rio to the red pen of the multimeter and we connected the green wire that goes into the PDP to the black pen. However, we got no continuity. We did the same for the yellow wire and still got no continuity.
- We also unplugged the two CAN wires from the Rio and measured resistance between them using a multimeter (hoping to get the total resistance of the CAN bus). We got 114 ohms, fairly close to the expected 120 Ohms from the termination resistor in the PDP.
Has anyone encountered this problem and if so, what are the ways that we can debug this problem?