SparkMAX CAN Transmit Error

We currently have an issue with our CAN bus when involving adding a 9th SparkMAX. When using only 8 SparkMAXes, we appear to have a properly functioning CAN Bus.

Using the REV Hardware client, we see there is a CAN Transmit Error and CAN Recieve Error once the 9th SparkMAX is added. Removing the extra SparkMAX gives us a “Bus Ok”. In both cases, Rev Hardware Client is recognizing all of the connected devices, so I don’t think its a connectivity issue.

In both cases, the driverstation shows a CAN utilization of about 38%. With 9 SparkMAXes, we see spikes of Recieve errors and the CAN Bus Off is 1, but the other fault categories stay at 0.

Finally, in the 8 SparkMAX configuration, the lights are solid cyan and magenta, which looks fine based on the Status LED Documentation. In the 9 SparkMAX configuration, the motor controllers continue to show magenta and cyan, but intermittently rapidly blink yellow. The closest I can see from the docs above is a CAN Fault, though notably there isn’t any orange and the blinking is rapid.

What we’ve tried:

  1. Swapping out the added SparkMAX with a spare.
  2. Swapping out the CAN wire.
  3. A combination of 1 and 2.

Has anyone else seen this issue?

I wonder what would happen if you unplugged a confirmed working sparkMAX and plugged in the odd one? Trying that might help give you a better sense of the scope of the issue. I have not seen this issue and have limited CAN knowledge but it’s just a thought.

Hi, I’ve experienced similar issues in the past. I’m not entirely sure how I ended up fixing this but you could try:

  1. Updating the new sparkMAX via the REV hardware client to the latest firmware
  2. You might have 2 (or more) sparks with the same can ID, you can also check this through the REV hardware client.
    Let me know if this works or not, I’m always happy to help!

We can double check the IDs but we did see all 9 spark maxes with the correct and unique IDs. We also swapped out the spark max with another with a completely different ID and same issue. Pretty sure they’re all updated but not a bad check either. @alex5572

We were facing a seemingly identical issue, including the “limit” on number of SparkMAXes and yellow rapidly blinking status lights.

We just resolved it by replacing one CANcoder that seemed to be causing the issue.

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