[wpilibc] Update C++ DiffDriveSim example to match Java (#2839)

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

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019-2020 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/kinematics/DifferentialDriveKinematics.h>
+#include <frc/system/plant/DCMotor.h>
+#include <frc/system/plant/LinearSystemId.h>
+#include <frc/trajectory/constraint/DifferentialDriveKinematicsConstraint.h>
+#include <units/acceleration.h>
+#include <units/angle.h>
+#include <units/length.h>
+#include <units/time.h>
+#include <units/velocity.h>
+#include <units/voltage.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 kLeftMotor1Port = 0;
+constexpr int kLeftMotor2Port = 1;
+constexpr int kRightMotor1Port = 2;
+constexpr int kRightMotor2Port = 3;
+
+constexpr int kLeftEncoderPorts[]{0, 1};
+constexpr int kRightEncoderPorts[]{2, 3};
+constexpr bool kLeftEncoderReversed = false;
+constexpr bool kRightEncoderReversed = true;
+
+constexpr auto kTrackwidth = 0.69_m;
+extern const frc::DifferentialDriveKinematics kDriveKinematics;
+
+constexpr int kEncoderCPR = 1024;
+constexpr auto kWheelDiameter = 6_in;
+constexpr double kEncoderDistancePerPulse =
+    // Assumes the encoders are directly mounted on the wheel shafts
+    (kWheelDiameter.to<double>() * wpi::math::pi) /
+    static_cast<double>(kEncoderCPR);
+
+// 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 Robot Characterization
+// Toolsuite provides a convenient tool for obtaining these values for your
+// robot.
+constexpr auto ks = 0.22_V;
+constexpr auto kv = 1.98 * 1_V * 1_s / 1_m;
+constexpr auto ka = 0.2 * 1_V * 1_s * 1_s / 1_m;
+
+constexpr auto kvAngular = 1.5 * 1_V * 1_s / 1_rad;
+constexpr auto kaAngular = 0.3 * 1_V * 1_s * 1_s / 1_rad;
+
+extern const frc::LinearSystem<2, 2, 2> kDrivetrainPlant;
+
+// Example values only -- use what's on your physical robot!
+constexpr auto kDrivetrainGearbox = frc::DCMotor::CIM(2);
+constexpr auto kDrivetrainGearing = 8.0;
+
+// Example value only - as above, this must be tuned for your drive!
+constexpr double kPDriveVel = 8.5;
+}  // namespace DriveConstants
+
+namespace AutoConstants {
+constexpr auto kMaxSpeed = 3_mps;
+constexpr auto kMaxAcceleration = 3_mps_sq;
+
+// Reasonable baseline values for a RAMSETE follower in units of meters and
+// seconds
+constexpr double kRamseteB = 2;
+constexpr double kRamseteZeta = 0.7;
+}  // namespace AutoConstants
+
+namespace OIConstants {
+constexpr int kDriverControllerPort = 1;
+}  // namespace OIConstants

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

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017-2020 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;
+  void SimulationPeriodic() 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/StateSpaceDifferentialDriveSimulation/include/RobotContainer.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019-2020 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/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();
+  const DriveSubsystem& GetRobotDrive() const;
+
+ 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;
+
+  frc2::InstantCommand m_driveHalfSpeed{[this] { m_drive.SetMaxOutput(0.5); },
+                                        {}};
+  frc2::InstantCommand m_driveFullSpeed{[this] { m_drive.SetMaxOutput(1); },
+                                        {}};
+
+  // The chooser for the autonomous routines
+  frc::SendableChooser<frc2::Command*> m_chooser;
+
+  void ConfigureButtonBindings();
+};

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

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019-2020 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/AnalogGyro.h>
+#include <frc/Encoder.h>
+#include <frc/PWMVictorSPX.h>
+#include <frc/SpeedControllerGroup.h>
+#include <frc/drive/DifferentialDrive.h>
+#include <frc/geometry/Pose2d.h>
+#include <frc/kinematics/DifferentialDriveOdometry.h>
+#include <frc/simulation/AnalogGyroSim.h>
+#include <frc/simulation/DifferentialDrivetrainSim.h>
+#include <frc/simulation/EncoderSim.h>
+#include <frc/simulation/Field2d.h>
+#include <frc2/command/SubsystemBase.h>
+#include <units/voltage.h>
+
+#include "Constants.h"
+
+class DriveSubsystem : public frc2::SubsystemBase {
+ public:
+  DriveSubsystem();
+
+  /**
+   * Will be called periodically whenever the CommandScheduler runs.
+   */
+  void Periodic() override;
+
+  /**
+   * Will be called periodically during simulation.
+   */
+  void SimulationPeriodic() override;
+
+  // Subsystem methods go here.
+
+  units::ampere_t GetCurrentDraw() const;
+
+  /**
+   * Drives the robot using arcade controls.
+   *
+   * @param fwd the commanded forward movement
+   * @param rot the commanded rotation
+   */
+  void ArcadeDrive(double fwd, double rot);
+
+  /**
+   * Controls each side of the drive directly with a voltage.
+   *
+   * @param left the commanded left output
+   * @param right the commanded right output
+   */
+  void TankDriveVolts(units::volt_t left, units::volt_t right);
+
+  /**
+   * Resets the drive encoders to currently read a position of 0.
+   */
+  void ResetEncoders();
+
+  /**
+   * Gets the average distance of the TWO encoders.
+   *
+   * @return the average of the TWO encoder readings
+   */
+  double GetAverageEncoderDistance();
+
+  /**
+   * Gets the left drive encoder.
+   *
+   * @return the left drive encoder
+   */
+  frc::Encoder& GetLeftEncoder();
+
+  /**
+   * Gets the right drive encoder.
+   *
+   * @return the right drive encoder
+   */
+  frc::Encoder& GetRightEncoder();
+
+  /**
+   * Sets the max output of the drive.  Useful for scaling the drive to drive
+   * more slowly.
+   *
+   * @param maxOutput the maximum output to which the drive will be constrained
+   */
+  void SetMaxOutput(double maxOutput);
+
+  /**
+   * Returns the heading of the robot.
+   *
+   * @return the robot's heading in degrees, from -180 to 180
+   */
+  units::degree_t GetHeading() const;
+
+  /**
+   * 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();
+
+  /**
+   * Returns the current wheel speeds of the robot.
+   *
+   * @return The current wheel speeds.
+   */
+  frc::DifferentialDriveWheelSpeeds GetWheelSpeeds();
+
+  /**
+   * Resets the odometry to the specified pose.
+   *
+   * @param pose The pose to which to set the odometry.
+   */
+  void ResetOdometry(frc::Pose2d pose);
+
+ private:
+  // Components (e.g. motor controllers and sensors) should generally be
+  // declared private and exposed only through public methods.
+
+  // The motor controllers
+  frc::PWMVictorSPX m_left1{DriveConstants::kLeftMotor1Port};
+  frc::PWMVictorSPX m_left2{DriveConstants::kLeftMotor2Port};
+  frc::PWMVictorSPX m_right1{DriveConstants::kRightMotor1Port};
+  frc::PWMVictorSPX m_right2{DriveConstants::kRightMotor2Port};
+
+  // The motors on the left side of the drive
+  frc::SpeedControllerGroup m_leftMotors{m_left1, m_left2};
+
+  // The motors on the right side of the drive
+  frc::SpeedControllerGroup m_rightMotors{m_right1, m_right2};
+
+  // The robot's drive
+  frc::DifferentialDrive m_drive{m_leftMotors, m_rightMotors};
+
+  // The left-side drive encoder
+  frc::Encoder m_leftEncoder{DriveConstants::kLeftEncoderPorts[0],
+                             DriveConstants::kLeftEncoderPorts[1]};
+
+  // The right-side drive encoder
+  frc::Encoder m_rightEncoder{DriveConstants::kRightEncoderPorts[0],
+                              DriveConstants::kRightEncoderPorts[1]};
+
+  // The gyro sensor
+  frc::AnalogGyro m_gyro{0};
+
+  // Odometry class for tracking robot pose
+  frc::DifferentialDriveOdometry m_odometry{m_gyro.GetRotation2d()};
+
+  // These classes help simulate our drivetrain.
+  frc::sim::DifferentialDrivetrainSim m_drivetrainSimulator{
+      DriveConstants::kDrivetrainPlant, DriveConstants::kTrackwidth,
+      DriveConstants::kDrivetrainGearbox, DriveConstants::kDrivetrainGearing,
+      DriveConstants::kWheelDiameter / 2};
+
+  frc::sim::EncoderSim m_leftEncoderSim{m_leftEncoder};
+  frc::sim::EncoderSim m_rightEncoderSim{m_rightEncoder};
+  frc::sim::AnalogGyroSim m_gyroAngleSim{m_gyro};
+
+  // The Field2d class simulates the field in the sim GUI. Note that we can have
+  // only one instance!
+  frc::Field2d m_fieldSim;
+};