Understanding How Code is Updated


I was wondering if someone could explain to me what a portion of the code does in my drive subsystem.

Specifically public Drive() {



Is this code executed whenever a method inside the subsystem is called?

import com.ctre.phoenix.motorcontrol.ControlMode;
import com.ctre.phoenix.motorcontrol.can.WPI_TalonSRX;
import com.kauailabs.navx.frc.AHRS;

import edu.wpi.first.wpilibj.SerialPort.Port;
import edu.wpi.first.wpilibj.SpeedController;
import edu.wpi.first.wpilibj.SpeedControllerGroup;
import edu.wpi.first.wpilibj.drive.DifferentialDrive;
import frc.robot.config.ElectricalConstants;
import frc.robot.config.RobotConfig;
import frc.robot.lib.KvLib;

//TODO: Change TalonSRXs to FXs
public class Drive {

    // TalonFX Motors
    public WPI_TalonSRX m_leftDriveSlave, m_rightDriveSlave, m_leftDriveMaster, m_rightDriveMaster;
    private KvLib kvLib;

    SpeedController leftDriveFrController = new WPI_TalonSRX(ElectricalConstants.m_leftDriveMaster);
    SpeedController leftDriveBackController = new WPI_TalonSRX(ElectricalConstants.m_leftDriveSlave);
    SpeedController rightDriveFrController = new WPI_TalonSRX(ElectricalConstants.m_rightDriveMaster);
    SpeedController rightDriveBackController = new WPI_TalonSRX(ElectricalConstants.m_rightDriveSlave);

    private SpeedControllerGroup leftDrive = new SpeedControllerGroup(leftDriveFrController, leftDriveBackController);
    private SpeedControllerGroup rightDrive = new SpeedControllerGroup(rightDriveFrController, rightDriveBackController);

    private DifferentialDrive drive;

    // anthony stuff below
    private AHRS s_NavX;

    public Drive() {

        this.m_leftDriveSlave = new WPI_TalonSRX(ElectricalConstants.m_leftDriveSlave);
        this.m_leftDriveMaster = new WPI_TalonSRX(ElectricalConstants.m_leftDriveMaster);
        this.m_rightDriveSlave = new WPI_TalonSRX(ElectricalConstants.m_rightDriveSlave);
        this.m_rightDriveMaster = new WPI_TalonSRX(ElectricalConstants.m_rightDriveMaster);


        this.s_NavX = new AHRS(Port.kMXP);
        this.kvLib = new KvLib();

        // Current limiting

        // TODO: Current limiting does not work
         * kvLib.setDriveTrainCurrentLimiting(m_leftDriveBack);
         * kvLib.setDriveTrainCurrentLimiting(m_leftDriveFront);
         * kvLib.setDriveTrainCurrentLimiting(m_rightDriveBack);
         * kvLib.setDriveTrainCurrentLimiting(m_rightDriveFront);
        // Differential drive
        drive = new DifferentialDrive(leftDrive, rightDrive);

    // @param resets the drive encoders
    public void reset() {

    public void move(double linearSpeed, double curveSpeed, boolean quickT) {
        if (s_NavX.getVelocityX() > 1.72 || s_NavX.getVelocityY() > 1.72) {
            drive.curvatureDrive(linearSpeed, curveSpeed, quickT);
        } else {
            drive.curvatureDrive(linearSpeed * RobotConfig.transmission, curveSpeed * RobotConfig.transmission, quickT);

    public void calibrate() {

    public void tankDrive(double leftSpeed, double rightSpeed) {
        drive.tankDrive(leftSpeed, rightSpeed);

     * Drive using two TalonSRX and adjustment values for horizontal and distance
     * correction
    public static void flyWithWires(WPI_TalonSRX starboard, WPI_TalonSRX port, double heading, double throttle) {
        starboard.set(ControlMode.Velocity, -1 * heading - throttle); // Set the starboard drivetrain motor to the steering power requirement added to the base speed
        port.set(ControlMode.Velocity, -1 * heading + throttle); // Does the same but on the other side


public Drive() {

method is called a constructor. The code inside it is only called once when the Drive subsystem is first created. This is the place for any motor initialization code that only needs to be done at the very beginning. Calling another method in the Drive class doesn’t run the code in the constructor again.

Let me know if you have any questions!


public Drive() is the Constructor of the Drive class.

It is called whenever another class instantiates a Drive object.


private Drive m_MyDrive = new Drive();

Thank you that was very helpful.

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