Open-Loop Quickstart

The below example showcases controlling a four-motor drivetrain.

Declaring Motor Controllers

The TalonFX motor controller constructor (Java, C++) requires a device ID (int) and an optional CAN bus (string).

Note

The name of the native roboRIO CAN bus is rio. This is also the default CAN bus on the roboRIO when none is specified.

Java

public class Robot extends TimedRobot {
   private static final String kCANBus = "canivore";

   private final TalonFX m_leftLeader = new TalonFX(0, kCANBus);
   private final TalonFX m_rightLeader = new TalonFX(1, kCANBus);
   private final TalonFX m_leftFollower = new TalonFX(2, kCANBus);
   private final TalonFX m_rightFollower = new TalonFX(3, kCANBus);
}

C++ (Header)

class Robot : public frc::TimedRobot {
private:
   static constexpr char const *kCANBus{"canivore"};

   ctre::phoenix6::hardware::TalonFX m_leftLeader{0, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_rightLeader{1, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_leftFollower{2, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_rightFollower{3, kCANBus};
}

Configure Followers & Inverts

In a traditional robot drivetrain, there are two motors attached to each horizontal side of the drivetrain. This setup typically (unless mechanically inverted) causes the right side to rotate in an opposite direction when given the same voltage.

Java

@Override
public void robotInit() {
   // start with factory-default configs
   var currentConfigs = new MotorOutputConfigs();

   // The left motor is CCW+
   currentConfigs.Inverted = InvertedValue.CounterClockwise_Positive;
   m_leftLeader.getConfigurator().apply(currentConfigs);

   // The right motor is CW+
   currentConfigs.Inverted = InvertedValue.Clockwise_Positive;
   m_rightLeader.getConfigurator().apply(currentConfigs);

   // Ensure our followers are following their respective leader
   m_leftFollower.setControl(new Follower(m_leftLeader.getDeviceID(), false));
   m_rightFollower.setControl(new Follower(m_rightLeader.getDeviceID(), false));
}

C++ (Source)

#include "Robot.h"

using namespace ctre::phoenix6;

void Robot::RobotInit() {
   // start with factory-default configs
   configs::MotorOutputConfigs currentConfigs{};

   // The left motor is CCW+
   currentConfigs.Inverted = signals::InvertedValue::CounterClockwise_Positive;
   m_leftLeader.GetConfigurator().Apply(currentConfigs);

   // The right motor is CW+
   currentConfigs.Inverted = signals::InvertedValue::Clockwise_Positive;
   m_rightLeader.GetConfigurator().Apply(currentConfigs);

   // Ensure the followers are following their respective leader
   m_leftFollower.SetControl(controls::Follower{m_leftLeader.GetDeviceID(), false});
   m_rightFollower.SetControl(controls::Follower{m_rightLeader.GetDeviceID(), false});
}

Full Example

Java

public class Robot extends TimedRobot {
   private static final String kCANBus = "canivore";

   private final TalonFX m_leftLeader = new TalonFX(0, kCANBus);
   private final TalonFX m_rightLeader = new TalonFX(1, kCANBus);
   private final TalonFX m_leftFollower = new TalonFX(2, kCANBus);
   private final TalonFX m_rightFollower = new TalonFX(3, kCANBus);

   private final DutyCycleOut m_leftOut = new DutyCycleOut(0);
   private final DutyCycleOut m_rightOut = new DutyCycleOut(0);

   private final XboxController m_driverJoy = new XboxController(0);

   @Override
   public void robotInit() {
      // start with factory-default configs
      var currentConfigs = new MotorOutputConfigs();

      // The left motor is CCW+
      currentConfigs.Inverted = InvertedValue.CounterClockwise_Positive;
      m_leftLeader.getConfigurator().apply(currentConfigs);

      // The right motor is CW+
      currentConfigs.Inverted = InvertedValue.Clockwise_Positive;
      m_rightLeader.getConfigurator().apply(currentConfigs);

      // Ensure our followers are following their respective leader
      m_leftFollower.setControl(new Follower(m_leftLeader.getDeviceID(), false));
      m_rightFollower.setControl(new Follower(m_rightLeader.getDeviceID(), false));
   }

   @Override
   public void teleopPeriodic() {
      // retrieve joystick inputs
      var fwd = -m_driverJoy.getLeftY();
      var rot = m_driverJoy.getRightX();

      // modify control requests
      m_leftOut.Output = fwd + rot;
      m_rightOut.Output = fwd - rot;

      // send control requests
      m_leftLeader.setControl(m_leftOut);
      m_rightLeader.setControl(m_rightOut);
   }
}

C++ (Source)

#include "Robot.h"

using namespace ctre::phoenix6;

void Robot::RobotInit() {
   // start with factory-default configs
   configs::MotorOutputConfigs currentConfigs{};

   // The left motor is CCW+
   currentConfigs.Inverted = signals::InvertedValue::CounterClockwise_Positive;
   m_leftLeader.GetConfigurator().Apply(currentConfigs);

   // The right motor is CW+
   currentConfigs.Inverted = signals::InvertedValue::Clockwise_Positive;
   m_rightLeader.GetConfigurator().Apply(currentConfigs);

   // Ensure the followers are following their respective leader
   m_leftFollower.SetControl(controls::Follower{m_leftLeader.GetDeviceID(), false});
   m_rightFollower.SetControl(controls::Follower{m_rightLeader.GetDeviceID(), false});
}

void Robot::TeleopPeriodic() {
   // retrieve joystick inputs
   auto fwd = -m_driverJoy.GetLeftY();
   auto rot = m_driverJoy.GetRightX();

   // modify control requests
   m_leftOut.Output = fwd + rot;
   m_rightOut.Output = fwd - rot;

   // send control requests
   m_leftLeader.SetControl(m_leftOut);
   m_rightLeader.SetControl(m_rightOut);
}

C++ (Header)

private:
   static constexpr char const *kCANBus{"canivore"};

   ctre::phoenix6::hardware::TalonFX m_leftLeader{0, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_rightLeader{1, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_leftFollower{2, kCANBus};
   ctre::phoenix6::hardware::TalonFX m_rightFollower{3, kCANBus};

   ctre::phoenix6::controls::DutyCycleOut m_leftOut{0};
   ctre::phoenix6::controls::DutyCycleOut m_rightOut{0};

   frc::XboxController m_driverJoy{0};