Spark MAX Velocity PID Problems

Technical Control System
1

We have been testing code for the Spark MAX controllers with the NEO brushless motors. We have found that when using the Velocity PID function built in to the Spark library that the controllers will, in the middle of running, briefly stop and then start again. The status LEDs appear to change for this brief instant from flashing green/red (moving) to blue/magenta (disabled brushless). We are updated to the most recent firmware version and we connected a single Spark MAX on the CAN, but the problem persists. At times, the sudden stop-start behavior seems to be correlated very closely with packet loss but sometimes without packet loss, this still happens. We are wondering if other teams are facing these issues and what they are doing to solve it. Thanks for any help.

2

There’s a known problem with CAN packets being dropped periodically. I don’t remember offhand if it was fixed in the last version, planned to be fixed in the next version, or if they’re still trying to track down the cause.

I’m sure one of the REV engineers will jump in to give a more concrete answer.

3

This sounds like it is momentarily losing a valid signal. In addition to looking at your packet loss, look at your wiring. Check the integrity of your CAN wiring and make sure your CAN bus is terminated at each end by the roboRIO and the PDP.

If you can, send us some pictures or your wiring to support@revrobotics.com.

4

To clarify, this was specifically on packets from the NEO to the roboRIO, and this issue has been confirmed fixed in firmware v1.0.384 and later. I have not recieved any reports of command packets being dropped (roboRIO to SPARK MAX).

5

Thanks for the correction. Apologies for the misinformation. Glad to hear it’s fixed

6

If it keeps persisting after the firmware update, my team faced a similar problem with the signal to the roborio which would drop out randomly in the middle of driving and create a problem similar to this with the TalonSRX’s try and see if the communication is always green when the Neo stops. It turned out that it was the laptop that was the problem as we had a bunch of chrome tabs open taking all of the processing power.

7