Add holonomic follower examples (#2052)

wpilibcExamples/src/main/cpp/examples/SwerveControllerCommand/include/subsystems/DriveSubsystem.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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#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

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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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#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}};
+};