Only alternating Spark Max work

hello, I am reaching out about our Spark Max’s. We have 6 Spark Max that we have created a CAN bus with. When you run the robot only the first, third, and fifth Sparks work from the CAN bus. We changed the order of the sparks but again the first, third, and fifth sparks in the bus worked. We have pushed new code, reinitialized them, and looked for solutions with nothing work. Are we missing something?

Hello! There are many possible root causes of the symptoms described. Have you gone through REV’s guides for troubleshooting? It has a number of procedures and ideas to try to help narrow down the cause.

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Yeah, I have gone through many of those troubleshoots but can’t seem to get the sparks to work.

Have you connected them to your computer with USB-C and configured them with the REV Hardware Client? If so, do they all show up in the client and have unique ID’s?

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If I’m reading that correctly then you’ve verified all of the Sparks are good (by changing positions), just that they don’t all work when you want them to? Can you link to a github repo with your code?

A photo of your wiring setup (emphasizing the CAN bus) wouldn’t hurt, either.

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I have put them in the REV Hardware Client and got a the first spark max located, I have it hooked up to the second, third, and fourth Spark Max. When plugged in, only the first and third spark max shows up but not the second or fourth Sparks.

we are not using Github, but we got it in a google drive, hopefully this is useful.

I suspect you have 3 different sets of ids assigned, and the first one in line responds, the second inline with the same id doesn’t. on your latest case, 1 and 2 likely have the same id, and 3 and 4 have the same id?


The code you uploaded is not valid. You do not have the REV vendor library installed and the file has nothing more than a package declaration.

I have a feeling you have duplicate IDs, but it could also be a wiring problem. Can you share a screenshot of the REV Hardware Client when you’re connected to the Sparks?

Suggested reading: Basic Setup and Configuration

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Got the code to work on google, should work now

This sounds like it could be a wiring issue, where the CAN H and CAN L wires are flipped at each junction, consistently throughout the chain. In other words, every other SPARK MAX is connected to the CAN bus backwards.

Send a photo of your wiring, and/or reach out to our support team at We’d be happy to help further troubleshooting!


we figured it out. Turned out to be a flipped connection. Thank you for the help!

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The post I made in another thread is relevant here since the cause of the problem was the same.

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