WPILib or External HAL Error: CAN: Message not found Start Follower Mode Command on Open Loop Arcade Command example

[roberttuttle]

The [config].follow(int | SparkBase) configuration option in the Beta 3 REVLib pre-release is reporting the following error when using/testing the Open Loop Arcade Command example for 2025 beta: [CAN SPARK] IDs: 2, 4, WPILib or External HAL Error: CAN: Message not found Start Follower Mode Command.

(Side note: when attempting to use the same configuration method to set a motor controller to follow a leader in RobotPy, the same error bubbled up causes an unhandled exception in Python and crashes the code. I started with that issue and then jumped over to the most recent example Java code to confirm or deny the same issue when trying to set follow).

[roberttuttle]

After migrating to WPILib Beta 3 and upgrading the example project (Java), simulation mode still generates the HAL error reported above. Python code no longer crashes, but reports the same HAL error now and handles the exception. I have not had a chance to deploy to a differential drive / tank physical robot to validate whether or not this is just a sim mode issue. Will do that after holiday break prior to season kickoff.

[jfabellera]

Looks like we're missing a sim handler for follower mode so it attempts to communicate with the device even while in simulation.

Follower mode was refactored while simulation was being overhauled, and we totally missed this. This will be fixed before kick off 🙂