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综合挑战Comprehensive Challenge

6.1 任务要求6.1 Task Requirements

把 Level 1 和 Level 2 学到的东西结合起来，写一个完整的遥控程序：Combine everything you've learned in Level 1 and Level 2 to write a complete driver control program:

      目标：Arcade 底盘 + 升降臂三位置状态机Goal: Arcade Drivetrain + 3-Position Lift State Machine
      底盘：左摇杆前后控制前进后退，右摇杆左右控制转弯（Arcade 模式）Drivetrain: left stick forward/backward, right stick turning (Arcade mode)
升降臂：R1 按一下切换到下一个位置（DOWN → MIDDLE → UP → DOWN...）Lift arm: press R1 to cycle to the next position (DOWN → MIDDLE → UP → DOWN...)
升降臂在后台线程里运行，不阻塞底盘操控Lift arm runs in a background thread, not blocking drivetrain control

    

6.2 分步提示6.2 Step-by-Step Hints

不知道怎么开始？按这个顺序来：Not sure where to start? Follow this order:

先定义 enum class LiftState，三个状态First define enum class LiftState with three states
写升降臂控制函数（while + switch），准备放到后台线程Write the lift control function (while + switch), ready for a background thread
写主循环：Arcade 底盘 + R1 按钮切换状态（记得边沿检测！）Write the main loop: Arcade drivetrain + R1 button to switch states (remember edge detection!)
在 main/opcontrol 里启动线程Start the thread in main/opcontrol

先自己试！Try It Yourself First!

在看参考答案之前，先自己写一遍。写不出来也没关系，但一定要先动手试。Before looking at the answer, write it yourself. It's okay if you can't finish it, but you must try first.

提示：把 Level 1 的 Arcade 底盘代码和 Level 2 的状态机代码拼在一起，就完成了大半。Hint: combine Level 1's Arcade drivetrain code with Level 2's state machine code, and you're mostly done.

6.3 参考答案6.3 Reference Answer

C++ (VEXcode)

// ===== 升降臂状态定义 =====
enum class LiftState { DOWN, MIDDLE, UP };
LiftState liftState = LiftState::DOWN;

// ===== 升降臂后台控制 =====
void liftControl() {
  while (true) {
    switch (liftState) {
      case LiftState::DOWN:
        LiftMotor.spinToPosition(0, degrees, false);
        break;
      case LiftState::MIDDLE:
        LiftMotor.spinToPosition(90, degrees, false);
        break;
      case LiftState::UP:
        LiftMotor.spinToPosition(180, degrees, false);
        break;
    }
    wait(20, msec);
  }
}

int main() {
  // 启动升降臂后台线程
  thread liftThread = thread(liftControl);

  // 主循环：底盘 + 按钮
  while (true) {
    // ----- Arcade 底盘 -----
    int forward = Controller1.Axis3.position();
    int turn    = Controller1.Axis1.position();
    int left    = forward + turn;
    int right   = forward - turn;
    LeftMotor.spin(fwd, left, percent);
    RightMotor.spin(fwd, right, percent);

    // ----- R1 切换升降臂状态（边沿检测） -----
    // VEXcode 可以用 PRESSED 回调，这里用简单写法
    // 实际中建议用回调方式
    wait(20, msec);
  }
}

// R1 回调函数（在 main 开头注册）
// Controller1.ButtonR1.pressed([]() {
//   switch (liftState) {
//     case LiftState::DOWN:   liftState = LiftState::MIDDLE; break;
//     case LiftState::MIDDLE: liftState = LiftState::UP;     break;
//     case LiftState::UP:     liftState = LiftState::DOWN;   break;
//   }
// });

C++ (VS Code)

// ===== 升降臂状态定义 =====
enum class LiftState { DOWN, MIDDLE, UP };
LiftState liftState = LiftState::DOWN;

// ===== 升降臂后台控制 =====
void liftControl() {
  while (true) {
    switch (liftState) {
      case LiftState::DOWN:
        LiftMotor.spinToPosition(0, degrees, false);
        break;
      case LiftState::MIDDLE:
        LiftMotor.spinToPosition(90, degrees, false);
        break;
      case LiftState::UP:
        LiftMotor.spinToPosition(180, degrees, false);
        break;
    }
    wait(20, msec);
  }
}

int main() {
  // 启动升降臂后台线程
  thread liftThread = thread(liftControl);

  // 边沿检测变量
  bool lastR1 = false;

  // 主循环
  while (true) {
    // ----- Arcade 底盘 -----
    int forward = Controller1.Axis3.position();
    int turn    = Controller1.Axis1.position();
    int left    = forward + turn;
    int right   = forward - turn;
    LeftMotor.spin(fwd, left, percent);
    RightMotor.spin(fwd, right, percent);

    // ----- R1 切换升降臂状态 -----
    bool currR1 = Controller1.ButtonR1.pressing();
    if (currR1 && !lastR1) {
      switch (liftState) {
        case LiftState::DOWN:   liftState = LiftState::MIDDLE; break;
        case LiftState::MIDDLE: liftState = LiftState::UP;     break;
        case LiftState::UP:     liftState = LiftState::DOWN;   break;
      }
    }
    lastR1 = currR1;

    wait(20, msec);
  }
}

C++ (PROS)

// ===== 升降臂状态定义 =====
enum class LiftState { DOWN, MIDDLE, UP };
LiftState liftState = LiftState::DOWN;

// ===== 升降臂后台控制 =====
void liftControl() {
  while (true) {
    switch (liftState) {
      case LiftState::DOWN:
        LiftMotor.move_absolute(0, 100);
        break;
      case LiftState::MIDDLE:
        LiftMotor.move_absolute(90, 100);
        break;
      case LiftState::UP:
        LiftMotor.move_absolute(180, 100);
        break;
    }
    pros::delay(20);
  }
}

void opcontrol() {
  // 启动升降臂后台线程
  pros::Task liftTask(liftControl);

  pros::Controller master(pros::E_CONTROLLER_MASTER);

  // 主循环
  while (true) {
    // ----- Arcade 底盘 -----
    int forward = master.get_analog(ANALOG_LEFT_Y);
    int turn    = master.get_analog(ANALOG_RIGHT_X);
    int left    = forward + turn;
    int right   = forward - turn;
    LeftMotor.move(left);
    RightMotor.move(right);

    // ----- R1 切换升降臂状态 -----
    if (master.get_digital_new_press(DIGITAL_R1)) {
      switch (liftState) {
        case LiftState::DOWN:   liftState = LiftState::MIDDLE; break;
        case LiftState::MIDDLE: liftState = LiftState::UP;     break;
        case LiftState::UP:     liftState = LiftState::DOWN;   break;
      }
    }

    pros::delay(20);
  }
}

        关键点回顾Key Points Review
        底盘在主循环控制 — 实时响应摇杆Drivetrain in the main loop — real-time joystick response
升降臂在后台线程运行 — 独立执行状态机Lift arm in a background thread — runs its state machine independently
状态切换在主循环做 — 用边沿检测避免跳档State switching in the main loop — use edge detection to prevent skipping
主循环只改变量，后台线程读变量执行动作 — 从不直接控制同一个电机Main loop only changes variables, background thread reads them and acts — never directly control the same motor from both

      

检查点：综合理解Checkpoint: Comprehensive Understanding

在上面的程序中，如果把升降臂控制代码直接写在主循环里（不用后台线程），会有什么问题？In the program above, what's the problem if you put the lift control code directly in the main loop (without a background thread)?