High Can Bus utilization

MSU2000 · October 13, 2024, 10:44pm

Currently, 14 Sparkmaxes on 14 motors. No other faults. The 2 NEOs on Shooters are running at the same rotation and setting. the 2 NEO 550s on for Intake are also running the same (one follower).

Tripled checked the wiring. Table below indicates the increase/decrease utilization when CAN connection is reduced.
Capture

What can I do to lower this threshold to acceptable number?

Reducing each status frame? Control Signal Frequency?

Reducing PID values?

Thanks

person4268 · October 13, 2024, 10:56pm

Reducing the status frames of things you don’t care about is probably a good first step. For instance, we set a higher interval for position status frames for motors that operated purely on velocity control, and vice versa. Your probably don’t care about the velocity of your swerve steer motors.

I think you can also set the control frame intervals but I think I don’t think you need to and it’s not super documented from what I can tell what it precisely does.

Also, avoid setting unnecessary things periodically if you are, like for instance pid constants or really anything that’s not a setpoint or duty cycle.

MSU2000 · October 13, 2024, 11:31pm

Is this done thru the code or can it be done thru REV hardware client when setting up the SparkMaxes?
Thanks

asid61 · October 13, 2024, 11:34pm

Either works.

jedgar6 · October 13, 2024, 11:38pm

Don’t forget that the through bore encoders are probably used instead of the neo 550’s.

MSU2000 · October 14, 2024, 1:57am

Which parameter in this list represents the status frame?

Thanks

Joe_Ross · October 14, 2024, 2:00am

None of them.

nevadexehs · October 14, 2024, 2:30am

im not sure where this code comes from but i had this on an old commit on our repo, feel free to take a look

github.com

vikings204/crescendo2024/blob/master/src/main/java/frc/lib/util/CANSparkMaxUtil.java

package frc.lib.util;

import com.revrobotics.CANSparkMax;
import com.revrobotics.CANSparkLowLevel;

/** Sets motor usage for a Spark Max motor controller */
public class CANSparkMaxUtil {
  public enum Usage {
    kAll,
    kPositionOnly,
    kVelocityOnly,
    kMinimal
  }

  /**
   * This function allows reducing a Spark Max's CAN bus utilization by reducing the periodic status
   * frame period of nonessential frames from 20ms to 500ms.
   *
   * <p>See
   * https://docs.revrobotics.com/sparkmax/operating-modes/control-interfaces#periodic-status-frames

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Tom_Line · October 14, 2024, 4:31am

Either works, but do it in code. Then when you swap a spark max you won’t get in trouble.

john3928 · October 14, 2024, 4:38am

FWIW, we set the intervals of all the messages we really don’t care about to large (relatively) prime numbers. If you just set them all to X, then every X ticks you get a burst of them. This really lowered our bus utilization. For next robot we bought a CANivore (I think that’s the name) that lets us have 2 separate CAN busses.

person4268 · October 14, 2024, 4:58am

Actually, i just took a further look and SPARK MAX Control Interfaces | REV ION Brushless states:

This rate can be changed manually in code, but unlike other parameters, this setting does not persist through a power cycle.

So, I think you need to set them in code. I’d go as far as refraining from making any status frames more frequent than normal in the case of a power loss event or similar so you’re not relying on the faster frame timing (some of my most annoying issues with revlib were re: it’s handling of missing status frames iirc).

MSU2000 · October 15, 2024, 4:59pm

Thank you!

We got it down to about 65% ish. A big one was what you suggested from swerve steer motors. We also tried big prime number. These seems to do the trick. Thanks again.