Measuring rotations of the wheel with encoders

[DuFish42]

I’m trying to make a command that drives forward a specified distance based on the drive wheel encoders. It uses very simple bang-bang controlling as I am just trying to get it functional, I don’t need it precise to the millimeter. This command can be found below:

public class DriveDistanceCommand extends CommandBase {
  /** Creates a new DriveDistanceCommand. */
  private DriveSubsystem driveSubsystem;
  private Translation2d translation;
  private double meters;
  private double cutoffTimeSeconds;
  private Timer timer;

  private double averageEncoderCount;

  public DriveDistanceCommand(DriveSubsystem driveSubsystem, Translation2d translation, double meters, double cutoffTimeSeconds) {
    this.driveSubsystem = driveSubsystem;
    this.translation = translation;
    this.meters = meters;
    this.cutoffTimeSeconds = cutoffTimeSeconds;
    timer = new Timer();

    addRequirements(driveSubsystem);
    // Use addRequirements() here to declare subsystem dependencies.
  }

  // Called when the command is initially scheduled.
  @Override
  public void initialize() {
    // resets encoders
    for(SwerveModule mod : driveSubsystem.mSwerveMods){
      mod.mDriveMotor.setSelectedSensorPosition(0);
    }

    timer.reset();
    timer.start();
  }

  // Called every time the scheduler runs while the command is scheduled.
  @Override
  public void execute() {
    driveSubsystem.drive(translation, 0, false, false);
    
    for(SwerveModule mod : driveSubsystem.mSwerveMods){
      averageEncoderCount += mod.getDriveMotorEncoder();
    }  
    averageEncoderCount /= 4;
  }

  // Called once the command ends or is interrupted.
  @Override
  public void end(boolean interrupted) {
    driveSubsystem.drive(new Translation2d(0, 0), 0, false, false);

    timer.stop();
    timer.reset();
  }

  // Returns true when the command should end.
  @Override
  public boolean isFinished() {
    if(timer.get() > 0){
      return Conversions.falconToMeters(averageEncoderCount) >= meters || timer.get() >= cutoffTimeSeconds;
    }
    return Conversions.falconToMeters(averageEncoderCount) >= meters;
  }
}

This logic flow works, at least in my head. The problem is that my encoders have a certain number of counts, and after that, I believe that they reset to 0. I can not confirm this as the build team is having problems with can wires and I haven’t been able to test anything for a while, but I certainly want to be prepared for it. Is there a simple way to get around this, or am I just going to have to make a variable that counts how many times the encoder has reset?

[otherguy]

Assuming you’re using falcon500 motors (given some of the method names), and reading the internal encoder values: the encoder does not roll over to zero after one revolution.

I.e. if you’re calling getSelectedSensorPosition() and the selected sensor is the internal encoder, then you won’t need to worry about it rolling over to zero in auto.

[DuFish42]

Fantastic, thanks for the help.