Add holonomic follower examples (#2052)

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/cpp/Robot.cpp

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "Robot.h"
+
+#include <frc/smartdashboard/SmartDashboard.h>
+#include <frc2/command/CommandScheduler.h>
+
+void Robot::RobotInit() {}
+
+/**
+ * This function is called every robot packet, no matter the mode. Use
+ * this for items like diagnostics that you want to run during disabled,
+ * autonomous, teleoperated and test.
+ *
+ * <p> This runs after the mode specific periodic functions, but before
+ * LiveWindow and SmartDashboard integrated updating.
+ */
+void Robot::RobotPeriodic() { frc2::CommandScheduler::GetInstance().Run(); }
+
+/**
+ * This function is called once each time the robot enters Disabled mode. You
+ * can use it to reset any subsystem information you want to clear when the
+ * robot is disabled.
+ */
+void Robot::DisabledInit() {}
+
+void Robot::DisabledPeriodic() {}
+
+/**
+ * This autonomous runs the autonomous command selected by your {@link
+ * RobotContainer} class.
+ */
+void Robot::AutonomousInit() {
+  m_autonomousCommand = m_container.GetAutonomousCommand();
+
+  if (m_autonomousCommand != nullptr) {
+    m_autonomousCommand->Schedule();
+  }
+}
+
+void Robot::AutonomousPeriodic() {}
+
+void Robot::TeleopInit() {
+  // This makes sure that the autonomous stops running when
+  // teleop starts running. If you want the autonomous to
+  // continue until interrupted by another command, remove
+  // this line or comment it out.
+  if (m_autonomousCommand != nullptr) {
+    m_autonomousCommand->Cancel();
+    m_autonomousCommand = nullptr;
+  }
+}
+
+/**
+ * This function is called periodically during operator control.
+ */
+void Robot::TeleopPeriodic() {}
+
+/**
+ * This function is called periodically during test mode.
+ */
+void Robot::TestPeriodic() {}
+
+#ifndef RUNNING_FRC_TESTS
+int main() { return frc::StartRobot<Robot>(); }
+#endif

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/cpp/RobotContainer.cpp

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "RobotContainer.h"
+
+#include <frc/controller/PIDController.h>
+#include <frc/geometry/Translation2d.h>
+#include <frc/shuffleboard/Shuffleboard.h>
+#include <frc/trajectory/Trajectory.h>
+#include <frc/trajectory/TrajectoryGenerator.h>
+#include <frc2/command/InstantCommand.h>
+#include <frc2/command/SequentialCommandGroup.h>
+#include <frc2/command/SwerveControllerCommand.h>
+#include <frc2/command/button/JoystickButton.h>
+#include <units/units.h>
+
+#include "Constants.h"
+#include "subsystems/DriveSubsystem.h"
+
+using namespace DriveConstants;
+
+RobotContainer::RobotContainer() {
+  // Initialize all of your commands and subsystems here
+
+  // Configure the button bindings
+  ConfigureButtonBindings();
+
+  // Set up default drive command
+  m_drive.SetDefaultCommand(frc2::RunCommand(
+      [this] {
+        m_drive.Drive(units::meters_per_second_t(
+                          m_driverController.GetY(frc::GenericHID::kLeftHand)),
+                      units::meters_per_second_t(
+                          m_driverController.GetY(frc::GenericHID::kRightHand)),
+                      units::radians_per_second_t(
+                          m_driverController.GetX(frc::GenericHID::kLeftHand)),
+                      false);
+      },
+      {&m_drive}));
+}
+
+void RobotContainer::ConfigureButtonBindings() {}
+
+frc2::Command* RobotContainer::GetAutonomousCommand() {
+  // Set up config for trajectory
+  frc::TrajectoryConfig config(AutoConstants::kMaxSpeed,
+                               AutoConstants::kMaxAcceleration);
+  // Add kinematics to ensure max speed is actually obeyed
+  config.SetKinematics(m_drive.kDriveKinematics);
+
+  // An example trajectory to follow.  All units in meters.
+  auto exampleTrajectory = frc::TrajectoryGenerator::GenerateTrajectory(
+      // Start at the origin facing the +X direction
+      frc::Pose2d(0_m, 0_m, frc::Rotation2d(0_deg)),
+      // Pass through these two interior waypoints, making an 's' curve path
+      {frc::Translation2d(1_m, 1_m), frc::Translation2d(2_m, -1_m)},
+      // End 3 meters straight ahead of where we started, facing forward
+      frc::Pose2d(3_m, 0_m, frc::Rotation2d(0_deg)),
+      // Pass the config
+      config);
+
+  frc2::SwerveControllerCommand<4> swerveControllerCommand(
+      exampleTrajectory, [this]() { return m_drive.GetPose(); },
+
+      m_drive.kDriveKinematics,
+
+      frc2::PIDController(AutoConstants::kPXController, 0, 0),
+      frc2::PIDController(AutoConstants::kPYController, 0, 0),
+      frc::ProfiledPIDController<units::radians>(
+          AutoConstants::kPThetaController, 0, 0,
+          AutoConstants::kThetaControllerConstraints),
+
+      [this](auto moduleStates) { m_drive.SetModuleStates(moduleStates); },
+
+      {&m_drive});
+
+  // no auto
+  return new frc2::SequentialCommandGroup(
+      std::move(swerveControllerCommand), std::move(swerveControllerCommand),
+      frc2::InstantCommand(
+          [this]() {
+            m_drive.Drive(units::meters_per_second_t(0),
+                          units::meters_per_second_t(0),
+                          units::radians_per_second_t(0), false);
+          },
+          {}));
+}

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/cpp/subsystems/DriveSubsystem.cpp

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "subsystems/DriveSubsystem.h"
+
+#include <frc/geometry/Rotation2d.h>
+#include <units/units.h>
+
+#include "Constants.h"
+
+using namespace DriveConstants;
+
+DriveSubsystem::DriveSubsystem()
+    : m_frontLeft{kFrontLeftDriveMotorPort,
+                  kFrontLeftTurningMotorPort,
+                  kFrontLeftDriveEncoderPorts,
+                  kFrontLeftTurningEncoderPorts,
+                  kFrontLeftDriveEncoderReversed,
+                  kFrontLeftTurningEncoderReversed},
+
+      m_rearLeft{
+          kRearLeftDriveMotorPort,       kRearLeftTurningMotorPort,
+          kRearLeftDriveEncoderPorts,    kRearLeftTurningEncoderPorts,
+          kRearLeftDriveEncoderReversed, kRearLeftTurningEncoderReversed},
+
+      m_frontRight{
+          kFrontRightDriveMotorPort,       kFrontRightTurningMotorPort,
+          kFrontRightDriveEncoderPorts,    kFrontRightTurningEncoderPorts,
+          kFrontRightDriveEncoderReversed, kFrontRightTurningEncoderReversed},
+
+      m_rearRight{
+          kRearRightDriveMotorPort,       kRearRightTurningMotorPort,
+          kRearRightDriveEncoderPorts,    kRearRightTurningEncoderPorts,
+          kRearRightDriveEncoderReversed, kRearRightTurningEncoderReversed},
+
+      m_odometry{kDriveKinematics,
+                 frc::Rotation2d(units::degree_t(GetHeading())),
+                 frc::Pose2d()} {}
+
+void DriveSubsystem::Periodic() {
+  // Implementation of subsystem periodic method goes here.
+  m_odometry.Update(frc::Rotation2d(units::degree_t(GetHeading())),
+                    m_frontLeft.GetState(), m_rearLeft.GetState(),
+                    m_frontRight.GetState(), m_rearRight.GetState());
+}
+
+void DriveSubsystem::Drive(units::meters_per_second_t xSpeed,
+                           units::meters_per_second_t ySpeed,
+                           units::radians_per_second_t rot,
+                           bool fieldRelative) {
+  auto states = kDriveKinematics.ToSwerveModuleStates(
+      fieldRelative ? frc::ChassisSpeeds::FromFieldRelativeSpeeds(
+                          xSpeed, ySpeed, rot,
+                          frc::Rotation2d(units::degree_t(GetHeading())))
+                    : frc::ChassisSpeeds{xSpeed, ySpeed, rot});
+
+  kDriveKinematics.NormalizeWheelSpeeds(&states, AutoConstants::kMaxSpeed);
+
+  auto [fl, fr, bl, br] = states;
+
+  m_frontLeft.SetDesiredState(fl);
+  m_frontRight.SetDesiredState(fr);
+  m_rearLeft.SetDesiredState(bl);
+  m_rearRight.SetDesiredState(br);
+}
+
+void DriveSubsystem::SetModuleStates(
+    std::array<frc::SwerveModuleState, 4> desiredStates) {
+  kDriveKinematics.NormalizeWheelSpeeds(&desiredStates,
+                                        AutoConstants::kMaxSpeed);
+  m_frontLeft.SetDesiredState(desiredStates[0]);
+  m_rearLeft.SetDesiredState(desiredStates[1]);
+  m_frontRight.SetDesiredState(desiredStates[2]);
+  m_rearRight.SetDesiredState(desiredStates[3]);
+}
+
+void DriveSubsystem::ResetEncoders() {
+  m_frontLeft.ResetEncoders();
+  m_rearLeft.ResetEncoders();
+  m_frontRight.ResetEncoders();
+  m_rearRight.ResetEncoders();
+}
+
+double DriveSubsystem::GetHeading() {
+  return std::remainder(m_gyro.GetAngle(), 360) * (kGyroReversed ? -1. : 1.);
+}
+
+void DriveSubsystem::ZeroHeading() { m_gyro.Reset(); }
+
+double DriveSubsystem::GetTurnRate() {
+  return m_gyro.GetRate() * (kGyroReversed ? -1. : 1.);
+}
+
+frc::Pose2d DriveSubsystem::GetPose() { return m_odometry.GetPose(); }
+
+void DriveSubsystem::ResetOdometry(frc::Pose2d pose) {
+  m_odometry.ResetPosition(pose,
+                           frc::Rotation2d(units::degree_t(GetHeading())));
+}

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/cpp/subsystems/SwerveModule.cpp

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "subsystems/SwerveModule.h"
+
+#include <frc/geometry/Rotation2d.h>
+#include <wpi/math>
+
+#include "Constants.h"
+
+SwerveModule::SwerveModule(int driveMotorChannel, int turningMotorChannel,
+                           const int driveEncoderPorts[],
+                           const int turningEncoderPorts[],
+                           bool driveEncoderReversed,
+                           bool turningEncoderReversed)
+    : m_driveMotor(driveMotorChannel),
+      m_turningMotor(turningMotorChannel),
+      m_driveEncoder(driveEncoderPorts[0], driveEncoderPorts[1]),
+      m_turningEncoder(turningEncoderPorts[0], turningEncoderPorts[1]),
+      m_reverseDriveEncoder(driveEncoderReversed),
+      m_reverseTurningEncoder(turningEncoderReversed) {
+  // Set the distance per pulse for the drive encoder. We can simply use the
+  // distance traveled for one rotation of the wheel divided by the encoder
+  // resolution.
+  m_driveEncoder.SetDistancePerPulse(
+      ModuleConstants::kDriveEncoderDistancePerPulse);
+
+  // Set the distance (in this case, angle) per pulse for the turning encoder.
+  // This is the the angle through an entire rotation (2 * wpi::math::pi)
+  // divided by the encoder resolution.
+  m_turningEncoder.SetDistancePerPulse(
+      ModuleConstants::kTurningEncoderDistancePerPulse);
+
+  // Limit the PID Controller's input range between -pi and pi and set the input
+  // to be continuous.
+  m_turningPIDController.EnableContinuousInput(units::radian_t(-wpi::math::pi),
+                                               units::radian_t(wpi::math::pi));
+}
+
+frc::SwerveModuleState SwerveModule::GetState() {
+  return {units::meters_per_second_t{m_driveEncoder.GetRate()},
+          frc::Rotation2d(units::radian_t(m_turningEncoder.Get()))};
+}
+
+void SwerveModule::SetDesiredState(frc::SwerveModuleState& state) {
+  // Calculate the drive output from the drive PID controller.
+  const auto driveOutput = m_drivePIDController.Calculate(
+      m_driveEncoder.GetRate(), state.speed.to<double>());
+
+  // Calculate the turning motor output from the turning PID controller.
+  auto turnOutput = m_turningPIDController.Calculate(
+      units::radian_t(m_turningEncoder.Get()), state.angle.Radians());
+
+  // Set the motor outputs.
+  m_driveMotor.Set(driveOutput);
+  m_turningMotor.Set(turnOutput);
+}
+
+void SwerveModule::ResetEncoders() {
+  m_driveEncoder.Reset();
+  m_turningEncoder.Reset();
+}

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/Constants.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include <frc/geometry/Translation2d.h>
+#include <frc/kinematics/SwerveDriveKinematics.h>
+#include <frc/trajectory/TrapezoidProfile.h>
+#include <units/units.h>
+#include <wpi/math>
+
+#pragma once
+
+/**
+ * The Constants header provides a convenient place for teams to hold robot-wide
+ * numerical or bool constants.  This should not be used for any other purpose.
+ *
+ * It is generally a good idea to place constants into subsystem- or
+ * command-specific namespaces within this header, which can then be used where
+ * they are needed.
+ */
+
+namespace DriveConstants {
+constexpr int kFrontLeftDriveMotorPort = 0;
+constexpr int kRearLeftDriveMotorPort = 2;
+constexpr int kFrontRightDriveMotorPort = 4;
+constexpr int kRearRightDriveMotorPort = 6;
+
+constexpr int kFrontLeftTurningMotorPort = 1;
+constexpr int kRearLeftTurningMotorPort = 3;
+constexpr int kFrontRightTurningMotorPort = 5;
+constexpr int kRearRightTurningMotorPort = 7;
+
+constexpr int kFrontLeftTurningEncoderPorts[2]{0, 1};
+constexpr int kRearLeftTurningEncoderPorts[2]{2, 3};
+constexpr int kFrontRightTurningEncoderPorts[2]{4, 5};
+constexpr int kRearRightTurningEncoderPorts[2]{5, 6};
+
+constexpr bool kFrontLeftTurningEncoderReversed = false;
+constexpr bool kRearLeftTurningEncoderReversed = true;
+constexpr bool kFrontRightTurningEncoderReversed = false;
+constexpr bool kRearRightTurningEncoderReversed = true;
+
+constexpr int kFrontLeftDriveEncoderPorts[2]{0, 1};
+constexpr int kRearLeftDriveEncoderPorts[2]{2, 3};
+constexpr int kFrontRightDriveEncoderPorts[2]{4, 5};
+constexpr int kRearRightDriveEncoderPorts[2]{5, 6};
+
+constexpr bool kFrontLeftDriveEncoderReversed = false;
+constexpr bool kRearLeftDriveEncoderReversed = true;
+constexpr bool kFrontRightDriveEncoderReversed = false;
+constexpr bool kRearRightDriveEncoderReversed = true;
+
+constexpr bool kGyroReversed = false;
+
+// These are example values only - DO NOT USE THESE FOR YOUR OWN ROBOT!
+// These characterization values MUST be determined either experimentally or
+// theoretically for *your* robot's drive. The RobotPy Characterization
+// Toolsuite provides a convenient tool for obtaining these values for your
+// robot.
+constexpr auto ks = 1_V;
+constexpr auto kv = 0.8 * 1_V * 1_s / 1_m;
+constexpr auto ka = 0.15 * 1_V * 1_s * 1_s / 1_m;
+
+// Example value only - as above, this must be tuned for your drive!
+constexpr double kPFrontLeftVel = 0.5;
+constexpr double kPRearLeftVel = 0.5;
+constexpr double kPFrontRightVel = 0.5;
+constexpr double kPRearRightVel = 0.5;
+}  // namespace DriveConstants
+
+namespace ModuleConstants {
+constexpr int kEncoderCPR = 1024;
+constexpr double kWheelDiameterMeters = .15;
+constexpr double kDriveEncoderDistancePerPulse =
+    // Assumes the encoders are directly mounted on the wheel shafts
+    (kWheelDiameterMeters * wpi::math::pi) / static_cast<double>(kEncoderCPR);
+
+constexpr double kTurningEncoderDistancePerPulse =
+    // Assumes the encoders are directly mounted on the wheel shafts
+    (wpi::math::pi * 2) / static_cast<double>(kEncoderCPR);
+
+constexpr double kPModuleTurningController = 1;
+constexpr double kPModuleDriveController = 1;
+}  // namespace ModuleConstants
+
+namespace AutoConstants {
+using radians_per_second_squared_t =
+    units::compound_unit<units::radians,
+                         units::inverse<units::squared<units::second>>>;
+
+constexpr auto kMaxSpeed = units::meters_per_second_t(3);
+constexpr auto kMaxAcceleration = units::meters_per_second_squared_t(3);
+constexpr auto kMaxAngularSpeed = units::radians_per_second_t(3.142);
+constexpr auto kMaxAngularAcceleration =
+    units::unit_t<radians_per_second_squared_t>(3.142);
+
+constexpr double kPXController = 0.5;
+constexpr double kPYController = 0.5;
+constexpr double kPThetaController = 0.5;
+
+//
+
+constexpr frc::TrapezoidProfile<units::radians>::Constraints
+    kThetaControllerConstraints{kMaxAngularSpeed, kMaxAngularAcceleration};
+
+}  // namespace AutoConstants
+
+namespace OIConstants {
+constexpr int kDriverControllerPort = 1;
+}  // namespace OIConstants

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/Robot.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/TimedRobot.h>
+#include <frc2/command/Command.h>
+
+#include "RobotContainer.h"
+
+class Robot : public frc::TimedRobot {
+ public:
+  void RobotInit() override;
+  void RobotPeriodic() override;
+  void DisabledInit() override;
+  void DisabledPeriodic() override;
+  void AutonomousInit() override;
+  void AutonomousPeriodic() override;
+  void TeleopInit() override;
+  void TeleopPeriodic() override;
+  void TestPeriodic() override;
+
+ private:
+  // Have it null by default so that if testing teleop it
+  // doesn't have undefined behavior and potentially crash.
+  frc2::Command* m_autonomousCommand = nullptr;
+
+  RobotContainer m_container;
+};

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/RobotContainer.h

@@ -0,0 +1,49 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/XboxController.h>
+#include <frc/controller/PIDController.h>
+#include <frc/controller/ProfiledPIDController.h>
+#include <frc/smartdashboard/SendableChooser.h>
+#include <frc2/command/Command.h>
+#include <frc2/command/InstantCommand.h>
+#include <frc2/command/PIDCommand.h>
+#include <frc2/command/ParallelRaceGroup.h>
+#include <frc2/command/RunCommand.h>
+
+#include "Constants.h"
+#include "subsystems/DriveSubsystem.h"
+
+/**
+ * This class is where the bulk of the robot should be declared.  Since
+ * Command-based is a "declarative" paradigm, very little robot logic should
+ * actually be handled in the {@link Robot} periodic methods (other than the
+ * scheduler calls).  Instead, the structure of the robot (including subsystems,
+ * commands, and button mappings) should be declared here.
+ */
+class RobotContainer {
+ public:
+  RobotContainer();
+
+  frc2::Command* GetAutonomousCommand();
+
+ private:
+  // The driver's controller
+  frc::XboxController m_driverController{OIConstants::kDriverControllerPort};
+
+  // The robot's subsystems and commands are defined here...
+
+  // The robot's subsystems
+  DriveSubsystem m_drive;
+
+  // The chooser for the autonomous routines
+  frc::SendableChooser<frc2::Command*> m_chooser;
+
+  void ConfigureButtonBindings();
+};

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/subsystems/DriveSubsystem.h

@@ -0,0 +1,120 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/ADXRS450_Gyro.h>
+#include <frc/Encoder.h>
+#include <frc/PWMVictorSPX.h>
+#include <frc/drive/MecanumDrive.h>
+#include <frc/geometry/Pose2d.h>
+#include <frc/geometry/Rotation2d.h>
+#include <frc/interfaces/Gyro.h>
+#include <frc/kinematics/ChassisSpeeds.h>
+#include <frc/kinematics/SwerveDriveKinematics.h>
+#include <frc/kinematics/SwerveDriveOdometry.h>
+#include <frc2/command/SubsystemBase.h>
+
+#include "Constants.h"
+#include "SwerveModule.h"
+
+class DriveSubsystem : public frc2::SubsystemBase {
+ public:
+  DriveSubsystem();
+
+  /**
+   * Will be called periodically whenever the CommandScheduler runs.
+   */
+  void Periodic() override;
+
+  // Subsystem methods go here.
+
+  /**
+   * Drives the robot at given x, y and theta speeds. Speeds range from [-1, 1]
+   * and the linear speeds have no effect on the angular speed.
+   *
+   * @param xSpeed        Speed of the robot in the x direction
+   *                      (forward/backwards).
+   * @param ySpeed        Speed of the robot in the y direction (sideways).
+   * @param rot           Angular rate of the robot.
+   * @param fieldRelative Whether the provided x and y speeds are relative to
+   *                      the field.
+   */
+  void Drive(units::meters_per_second_t xSpeed,
+             units::meters_per_second_t ySpeed, units::radians_per_second_t rot,
+             bool feildRelative);
+
+  /**
+   * Resets the drive encoders to currently read a position of 0.
+   */
+  void ResetEncoders();
+
+  /**
+   * Sets the drive SpeedControllers to a power from -1 to 1.
+   */
+  void SetModuleStates(std::array<frc::SwerveModuleState, 4> desiredStates);
+
+  /**
+   * Returns the heading of the robot.
+   *
+   * @return the robot's heading in degrees, from 180 to 180
+   */
+  double GetHeading();
+
+  /**
+   * Zeroes the heading of the robot.
+   */
+  void ZeroHeading();
+
+  /**
+   * Returns the turn rate of the robot.
+   *
+   * @return The turn rate of the robot, in degrees per second
+   */
+  double GetTurnRate();
+
+  /**
+   * Returns the currently-estimated pose of the robot.
+   *
+   * @return The pose.
+   */
+  frc::Pose2d GetPose();
+
+  /**
+   * Resets the odometry to the specified pose.
+   *
+   * @param pose The pose to which to set the odometry.
+   */
+  void ResetOdometry(frc::Pose2d pose);
+
+  units::meter_t kTrackWidth =
+      .5_m;  // Distance between centers of right and left wheels on robot
+  units::meter_t kWheelBase =
+      .7_m;  // Distance between centers of front and back wheels on robot
+
+  frc::SwerveDriveKinematics<4> kDriveKinematics{
+      frc::Translation2d(kWheelBase / 2, kTrackWidth / 2),
+      frc::Translation2d(kWheelBase / 2, -kTrackWidth / 2),
+      frc::Translation2d(-kWheelBase / 2, kTrackWidth / 2),
+      frc::Translation2d(-kWheelBase / 2, -kTrackWidth / 2)};
+
+ private:
+  // Components (e.g. motor controllers and sensors) should generally be
+  // declared private and exposed only through public methods.
+
+  SwerveModule m_frontLeft;
+  SwerveModule m_rearLeft;
+  SwerveModule m_frontRight;
+  SwerveModule m_rearRight;
+
+  // The gyro sensor
+  frc::ADXRS450_Gyro m_gyro;
+
+  // Odometry class for tracking robot pose
+  // 4 defines the number of modules
+  frc::SwerveDriveOdometry<4> m_odometry;
+};

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/subsystems/SwerveModule.h

@@ -0,0 +1,65 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/Encoder.h>
+#include <frc/Spark.h>
+#include <frc/controller/PIDController.h>
+#include <frc/controller/ProfiledPIDController.h>
+#include <frc/geometry/Rotation2d.h>
+#include <frc/kinematics/SwerveModuleState.h>
+#include <frc/trajectory/TrapezoidProfile.h>
+#include <wpi/math>
+
+#include "Constants.h"
+
+class SwerveModule {
+  using radians_per_second_squared_t =
+      units::compound_unit<units::radians,
+                           units::inverse<units::squared<units::second>>>;
+
+ public:
+  SwerveModule(int driveMotorChannel, int turningMotorChannel,
+               const int driveEncoderPorts[2], const int turningEncoderPorts[2],
+               bool driveEncoderReversed, bool turningEncoderReversed);
+
+  frc::SwerveModuleState GetState();
+
+  void SetDesiredState(frc::SwerveModuleState& state);
+
+  void ResetEncoders();
+
+ private:
+  // We have to use meters here instead of radians due to the fact that
+  // ProfiledPIDController's constraints only take in meters per second and
+  // meters per second squared.
+
+  static constexpr units::radians_per_second_t kModuleMaxAngularVelocity =
+      units::radians_per_second_t(wpi::math::pi);  // radians per second
+  static constexpr units::unit_t<radians_per_second_squared_t>
+      kModuleMaxAngularAcceleration =
+          units::unit_t<radians_per_second_squared_t>(
+              wpi::math::pi * 2.0);  // radians per second squared
+
+  frc::Spark m_driveMotor;
+  frc::Spark m_turningMotor;
+
+  frc::Encoder m_driveEncoder;
+  frc::Encoder m_turningEncoder;
+
+  bool m_reverseDriveEncoder;
+  bool m_reverseTurningEncoder;
+
+  frc2::PIDController m_drivePIDController{
+      ModuleConstants::kPModuleDriveController, 0, 0};
+  frc::ProfiledPIDController<units::radians> m_turningPIDController{
+      ModuleConstants::kPModuleTurningController,
+      0.0,
+      0.0,
+      {kModuleMaxAngularVelocity, kModuleMaxAngularAcceleration}};
+};