PDP still supplying power to all ports but CAN doesn't work

Hey so we have an old CTRE PDP which I found a while back in our backrooms of our class, and when I went to plug it in, I saw the CAN on it wasn’t working. Not just can but the lights wouldn’t go on at all. I tested all the power delivery channels and everything seems to be working fine, but it still sucks that it won’t be legal to use in comp cause the can control on that doesn’t even work. I took it apart too and when I looked at the smaller daughterboard on it meant for can, i couldn’t see any obvious signs of something on the inside blowing up. I don’t care about it too much since we already have an extra PDP and right now im just using the broken one for training my subteam and as a test bench, but if anyone has any ideas to what happened to it can someone let me know? Thanks.

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The CTRE PDP doesn’t switch power to any port under CAN control. The CAN bus just reports currents and that there is a PDP in the system (maybe some other stuff too).
The CAN circuitry might have been damaged by hooking up the input power in reverse accidentally. The “distribution” part would still work because it’s just wires but the CAN part could be damaged.

What rule requires CAN to be working on the PDP?

R716 “ Connect the PDP/PDH to the roboRIO CAN bus. The PDP/PDH CAN interface must be connected to the built-in CAN bus on the roboRIO (either directly or daisy-chained via another CAN bus device).”

The PDP doesn’t feature CAN control. It features CAN to provide current monitoring (both for individual channels and the overall current draw) and to provide an easy solution for a termination resistor at the end of the bus.

What are you trying to do that makes you sure the CAN bus isn’t working? Just looking for it over Phoenix Tuner?

I’m not actually sure this is an answer; it doesn’t technically require CAN to be working, just connected. It’s been a few years since I’ve seen an inspector check the PDP firmware in the DS as well, which is the only quick way they’d know if it were functional; nowadays they just make sure it’s physically wired to the bus.

As a CSA, I’d appreciate if all teams had working PDP/PDH CAN connections so that current draw is properly recorded in the DS logs, but I don’t think I can say it’s required.

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Usual disclaimer that I am not FIRST or the GDC and I am not a source of truth for rules unlike the manual or official Q&A.

That said I was involved in working with FIRST on the wording of this rule the last time it was changed - the intent is that “Connect” means electrically connect the wires. CAN does not actually have to be functioning, the wires just have to be connected.

This change was made a few years ago to explicitly address the situation where a team may have a damaged smart module in the PDP. This way you’re not legally required to purchase a new PDP just because yours doesn’t report current (but functions fine otherwise).

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Yeah that makes sense

Ah yeah my bad. I will ask one of the inspectors what they think about the broken CAN on the PDP at our waterloo comp

Since our current robot has a lot of high power motors I don’t think it’ll be worth the risk by connecting the bad PDP to our bot

I’ll confirm again 100% if the can monitoring board is completely dead but as of now, it’s just the lights which don’t turn on at all

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