How to better understand can bus information

Technical CAN
1

been looking into a debug tool to understand can bus problems better (like when one link shorts the entire can bus network).

in this season our lost coms several teams so if teams found a good way to analyze problems and can share it here it would be appreciated.

2

I don’t know of any software exactly like what you’re talking about, but Phoenix Tuner and REV Hardware client are good places to start.

3

Other than the two vendor tools mentioned by @IanSzalai, I’m not aware of any tools specifically for that, or at least nothing I use when assisting teams as a CSA. The most common issue teams experience is related to the wiring, so software won’t be much help. That said, the best way to troubleshoot something is to understand how it works.

Know the order devices exist on the bus. If a set of them all stop working, and you know theyre the last 3 on the bus (from the perspective of the rio), then you likely have a break right before the 3rd-to-last one. If the 3 are in the middle, then you might have the green/yellow wires flipped twice.

Work with the electrical group to ensure connections are solid. Use gendered connectors and be consistent in how theyre applied to reduce likelihood of polarity flip-flops. Use good crimping and soldering practices to ensure connections are solid. Use good wire management practices to minimize chances of wires wiggling loose or getting caught up in other mechanisms or by other bots.

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4

For issues such as shorts, there are two approaches I usually follow:

  1. use something like REV H/W Client (which does have a simple CAN sniffer in it, but usually more interesting is just “what is showing up on the bus?”) and wiggle and/or binary search to find problems;
  2. I have one of these. If you get to know how things look on a healthy CAN bus, something like this can visually show when things are less good.
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5

For shorts, use a multimeter and check the resistance across High and Low.

For everything else, Phoenix and Rev have good tools. I plan on using Vspy for educational purposes, but that’s iverkill

6

Also use the multimeter for continuity testing. This is an excellent way to narrow down the location of your issue.

7

I haven’t had the chance to check it out, but Wireshark CAN Monitor looks to have lots of potential.

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8

It’s been abandoned for a while by the looks of it, I intend to pick it up and update when i get my garage shop up and running or extended access to a robot. I may rewrite the dissectors in lua though simply because it’s shorter and easy to understand for students.

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9

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