Motor Control Example

Basic motor control with joystick input and encoder feedback

This example demonstrates:

• Controlling a motor with joystick input
• Reading encoder values
• Converting encoder ticks to distance
• Sending data to SmartDashboard

Complete Example

Java

package edu.wpi.first.wpilibj.examples.motorcontrol;

import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.Joystick;
import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.motorcontrol.PWMSparkMax;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

/**
 * This sample program shows how to control a motor using a joystick. In the operator control part
 * of the program, the joystick is read and the value is written to the motor.
 *
 * Joystick analog values range from -1 to 1 and motor controller inputs also range from -1 to 1
 * making it easy to work together.
 *
 * In addition, the encoder value of an encoder connected to ports 0 and 1 is consistently sent
 * to the Dashboard.
 */
public class Robot extends TimedRobot {
  private static final int kMotorPort = 0;
  private static final int kJoystickPort = 0;
  private static final int kEncoderPortA = 0;
  private static final int kEncoderPortB = 1;

  private final PWMSparkMax m_motor;
  private final Joystick m_joystick;
  private final Encoder m_encoder;

  public Robot() {
    m_motor = new PWMSparkMax(kMotorPort);
    m_joystick = new Joystick(kJoystickPort);
    m_encoder = new Encoder(kEncoderPortA, kEncoderPortB);
    // Use SetDistancePerPulse to set the multiplier for GetDistance
    // This is set up assuming a 6 inch wheel with a 360 CPR encoder.
    m_encoder.setDistancePerPulse((Math.PI * 6) / 360.0);
  }

  @Override
  public void robotPeriodic() {
    SmartDashboard.putNumber("Encoder", m_encoder.getDistance());
  }

  @Override
  public void teleopPeriodic() {
    m_motor.set(m_joystick.getY());
  }
}

C++

#include <numbers>

#include <frc/Encoder.h>
#include <frc/Joystick.h>
#include <frc/TimedRobot.h>
#include <frc/motorcontrol/PWMSparkMax.h>
#include <frc/smartdashboard/SmartDashboard.h>

/**
 * This sample program shows how to control a motor using a joystick. In the
 * operator control part of the program, the joystick is read and the value is
 * written to the motor.
 *
 * Joystick analog values range from -1 to 1 and motor controller inputs as
 * range from -1 to 1 making it easy to work together.
 *
 * In addition, the encoder value of an encoder connected to ports 0 and 1 is
 * consistently sent to the Dashboard.
 */
class Robot : public frc::TimedRobot {
 public:
  void TeleopPeriodic() override { m_motor.Set(m_stick.GetY()); }

  void RobotPeriodic() override {
    frc::SmartDashboard::PutNumber("Encoder", m_encoder.GetDistance());
  }

  Robot() {
    // Use SetDistancePerPulse to set the multiplier for GetDistance
    // This is set up assuming a 6 inch wheel with a 360 CPR encoder.
    m_encoder.SetDistancePerPulse((std::numbers::pi * 6) / 360.0);
  }

 private:
  frc::Joystick m_stick{0};
  frc::PWMSparkMax m_motor{0};
  frc::Encoder m_encoder{0, 1};
};

#ifndef RUNNING_FRC_TESTS
int main() {
  return frc::StartRobot<Robot>();
}
#endif

What This Example Demonstrates

Motor Control

The motor controller accepts values from -1.0 to 1.0:

• 1.0 = full speed forward
• 0.0 = stopped
• -1.0 = full speed reverse

The joystick Y-axis returns values in the same range, making direct control simple.

Encoder Setup

Encoders measure rotation with “counts per revolution” (CPR). To convert to distance:

m_encoder.setDistancePerPulse((Math.PI * 6) / 360.0);

This example assumes:

• 6-inch diameter wheel
• 360 CPR encoder
• Distance in inches

Formula: (π × diameter) / counts_per_revolution

SmartDashboard

robotPeriodic() runs in all modes (disabled, autonomous, teleop, test). This makes it perfect for updating dashboard values continuously.

Running in Simulation

1. Open SmartDashboard or Shuffleboard
2. Enable the robot in teleoperated mode
3. Move the joystick to control the motor
4. Watch the encoder distance value update on the dashboard

Source Location

• Java: wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/motorcontrol/Robot.java
• C++: wpilibcExamples/src/main/cpp/examples/MotorControl/cpp/Robot.cpp