allwpilib/wpilibcExamples/src/main/cpp/examples/SimpleDifferentialDriveSimulation/include/Drivetrain.h

// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.

#pragma once

#include <frc/AnalogGyro.h>
#include <frc/Encoder.h>
#include <frc/controller/PIDController.h>
#include <frc/controller/SimpleMotorFeedforward.h>
#include <frc/kinematics/DifferentialDriveKinematics.h>
#include <frc/kinematics/DifferentialDriveOdometry.h>
#include <frc/motorcontrol/MotorControllerGroup.h>
#include <frc/motorcontrol/PWMSparkMax.h>
#include <frc/simulation/AnalogGyroSim.h>
#include <frc/simulation/DifferentialDrivetrainSim.h>
#include <frc/simulation/EncoderSim.h>
#include <frc/smartdashboard/Field2d.h>
#include <frc/smartdashboard/SmartDashboard.h>
#include <frc/system/plant/LinearSystemId.h>
#include <units/angle.h>
#include <units/angular_velocity.h>
#include <units/length.h>
#include <units/velocity.h>
#include <wpi/numbers>

/**
 * Represents a differential drive style drivetrain.
 */
class Drivetrain {
 public:
  Drivetrain() {
    m_gyro.Reset();
    // Set the distance per pulse for the drive encoders. We can simply use the
    // distance traveled for one rotation of the wheel divided by the encoder
    // resolution.
    m_leftEncoder.SetDistancePerPulse(2 * wpi::numbers::pi * kWheelRadius /
                                      kEncoderResolution);
    m_rightEncoder.SetDistancePerPulse(2 * wpi::numbers::pi * kWheelRadius /
                                       kEncoderResolution);

    m_leftEncoder.Reset();
    m_rightEncoder.Reset();

    m_rightGroup.SetInverted(true);

    frc::SmartDashboard::PutData("Field", &m_fieldSim);
  }

  static constexpr units::meters_per_second_t kMaxSpeed =
      3.0_mps;  // 3 meters per second
  static constexpr units::radians_per_second_t kMaxAngularSpeed{
      wpi::numbers::pi};  // 1/2 rotation per second

  void SetSpeeds(const frc::DifferentialDriveWheelSpeeds& speeds);
  void Drive(units::meters_per_second_t xSpeed,
             units::radians_per_second_t rot);
  void UpdateOdometry();
  void ResetOdometry(const frc::Pose2d& pose);

  frc::Pose2d GetPose() const { return m_odometry.GetPose(); }

  void SimulationPeriodic();
  void Periodic();

 private:
  static constexpr units::meter_t kTrackWidth = 0.381_m * 2;
  static constexpr double kWheelRadius = 0.0508;  // meters
  static constexpr int kEncoderResolution = 4096;

  frc::PWMSparkMax m_leftLeader{1};
  frc::PWMSparkMax m_leftFollower{2};
  frc::PWMSparkMax m_rightLeader{3};
  frc::PWMSparkMax m_rightFollower{4};

  frc::MotorControllerGroup m_leftGroup{m_leftLeader, m_leftFollower};
  frc::MotorControllerGroup m_rightGroup{m_rightLeader, m_rightFollower};

  frc::Encoder m_leftEncoder{0, 1};
  frc::Encoder m_rightEncoder{2, 3};

  frc2::PIDController m_leftPIDController{8.5, 0.0, 0.0};
  frc2::PIDController m_rightPIDController{8.5, 0.0, 0.0};

  frc::AnalogGyro m_gyro{0};

  frc::DifferentialDriveKinematics m_kinematics{kTrackWidth};
  frc::DifferentialDriveOdometry m_odometry{m_gyro.GetRotation2d()};

  // Gains are for example purposes only - must be determined for your own
  // robot!
  frc::SimpleMotorFeedforward<units::meters> m_feedforward{1_V, 3_V / 1_mps};

  // Simulation classes help us simulate our robot
  frc::sim::AnalogGyroSim m_gyroSim{m_gyro};
  frc::sim::EncoderSim m_leftEncoderSim{m_leftEncoder};
  frc::sim::EncoderSim m_rightEncoderSim{m_rightEncoder};
  frc::Field2d m_fieldSim;
  frc::LinearSystem<2, 2, 2> m_drivetrainSystem =
      frc::LinearSystemId::IdentifyDrivetrainSystem(
          1.98_V / 1_mps, 0.2_V / 1_mps_sq, 1.5_V / 1_rad_per_s,
          0.3_V / 1_rad_per_s_sq);
  frc::sim::DifferentialDrivetrainSim m_drivetrainSimulator{
      m_drivetrainSystem, kTrackWidth, frc::DCMotor::CIM(2), 8, 2_in};
};