# ROS2 Driver Observe

**What you’ll do**
- ROS2 `cmd_vel`을 받아 `setCommand(v, omega)`를 업데이트합니다.
- `Driver` 수신 큐를 처리해 `vehicle_speed`, `battery_voltage` 토픽을 발행합니다.
- 마지막 명령을 주기적으로 재전송할 수 있습니다.

**Prerequisites**
- ROS2 환경
- {doc}`ROS2 Driver Demo </page/SDK/tutorials/ros2_driver_demo>`

**Next**
- {doc}`ROS2 Driver Read AllState </page/SDK/tutorials/ros2_driver_read_allstate>`
- {doc}`ROS2 High Rate Control </page/SDK/tutorials/ros2_high_rate_control>`

---

이 튜토리얼은 `driver_observe` 예제를 ROS2 노드로 옮겨,
속도/배터리를 토픽으로 발행하는 구조를 단계별로 만들고 이해하는 데 집중합니다.

## 목표
1. ROS2 노드에서 Driver 시작
2. `/cmd_vel`을 구독해 `setCommand(v, omega)` 업데이트
3. Driver 수신 큐를 drain 해서 `/vehicle_speed`, `/battery_voltage` 발행
4. 마지막 명령을 주기적으로 재전송 (선택)

---

## 단계별 구현 가이드

### 단계 1) include 준비

```cpp
#include "KMC_driver.hpp"

#include <rclcpp/rclcpp.hpp>
#include <geometry_msgs/msg/twist.hpp>
#include <std_msgs/msg/float32.hpp>

#include <chrono>
#include <optional>
#include <string>
```

---

### 단계 2) 노드 클래스 뼈대

```cpp
class KmcHardwareDriverObserveNode final : public rclcpp::Node {
public:
  KmcHardwareDriverObserveNode() : Node("kmc_hardware_driver_observe_node") {
    // 다음 단계에서 파라미터/Driver 설정을 채운다.
  }

  ~KmcHardwareDriverObserveNode() override { driver_.stop(); }

private:
  KMC_HARDWARE::Driver driver_;
};
```

---

### 단계 3) 멤버 변수 준비

```cpp
  rclcpp::Publisher<std_msgs::msg::Float32>::SharedPtr speed_pub_;
  rclcpp::Publisher<std_msgs::msg::Float32>::SharedPtr battery_pub_;
  rclcpp::Subscription<geometry_msgs::msg::Twist>::SharedPtr cmd_sub_;
  rclcpp::TimerBase::SharedPtr rx_timer_;
  rclcpp::TimerBase::SharedPtr cmd_timer_;

  std::string port_;
  int baud_{921600};
  double control_rate_hz_{100.0};
  double vehicle_speed_rate_hz_{50.0};
  int command_timeout_ms_{200};
  double command_refresh_hz_{50.0};
  int realtime_priority_{-1};
  int cpu_affinity_{-1};
  double battery_hz_{1.0};

  float last_cmd_v_{0.0f};
  float last_cmd_w_{0.0f};
  std::optional<rclcpp::Time> last_cmd_received_;
```

---

### 단계 4) 파라미터 선언

```cpp
    port_ = declare_parameter<std::string>("port", "/dev/ttyKMC");
    baud_ = declare_parameter<int>("baud", 921600);
    control_rate_hz_ = declare_parameter<double>("control_rate_hz", 100.0);
    vehicle_speed_rate_hz_ = declare_parameter<double>("vehicle_speed_rate_hz", 50.0);
    command_timeout_ms_ = declare_parameter<int>("command_timeout_ms", 200);
    command_refresh_hz_ = declare_parameter<double>("command_refresh_hz", 50.0);
    realtime_priority_ = declare_parameter<int>("realtime_priority", -1);
    cpu_affinity_ = declare_parameter<int>("cpu_affinity", -1);
    battery_hz_ = declare_parameter<double>("battery_hz", 1.0);
```

---

### 단계 5) Driver 옵션 구성 + 시작
배터리 요청 주기(`battery_hz`)도 옵션에 반영합니다.
옵션 필드 의미는 {ref}`Driver::Options <sdk-driver-options>`를 기준으로 합니다.

```cpp
    KMC_HARDWARE::Driver::Options opt;
    opt.port = port_;
    opt.serial.baudrate = baud_;
    opt.serial.hw_flow_control = true;
    opt.control_rate_hz = control_rate_hz_;
    opt.vehicle_speed_rate_hz = vehicle_speed_rate_hz_;
    opt.command_timeout_ms = command_timeout_ms_;
    opt.realtime_priority = realtime_priority_;
    opt.cpu_affinity = cpu_affinity_;

    opt.poll_battery = battery_hz_ > 0.0;
    opt.battery_rate_hz = battery_hz_ > 0.0 ? battery_hz_ : 1.0;

    if (!driver_.start(opt)) {
      throw std::runtime_error("Failed to open UART port: " + port_);
    }
```

---

### 단계 6) 토픽 구성
속도와 배터리 토픽을 발행할 퍼블리셔를 만들고,
`/cmd_vel`을 구독해 `setCommand()`로 전달합니다.

```cpp
    speed_pub_ = create_publisher<std_msgs::msg::Float32>("vehicle_speed", 10);
    battery_pub_ = create_publisher<std_msgs::msg::Float32>("battery_voltage", 10);

    cmd_sub_ = create_subscription<geometry_msgs::msg::Twist>(
        "cmd_vel", 10, [this](geometry_msgs::msg::Twist::SharedPtr msg) {
          const float v = static_cast<float>(msg->linear.x);
          const float w = static_cast<float>(msg->angular.z);
          last_cmd_v_ = v;
          last_cmd_w_ = w;
          last_cmd_received_ = now();
          driver_.setCommand(v, w);
        });
```

---

### 단계 7) 수신 큐 drain 함수
Driver의 수신 큐에서 메시지를 꺼내서 종류별로 publish 합니다.

```cpp
  void drainDriverQueue() {
    for (int i = 0; i < 100; ++i) {
      auto msg = driver_.tryPopMessage();
      if (!msg) break;

      if (auto* vs = std::get_if<KMC_HARDWARE::VehicleSpeed>(&*msg)) {
        std_msgs::msg::Float32 out;
        out.data = vs->mps;
        speed_pub_->publish(out);
      } else if (auto* bv = std::get_if<KMC_HARDWARE::BatteryVoltage>(&*msg)) {
        std_msgs::msg::Float32 out;
        out.data = bv->volt;
        battery_pub_->publish(out);
      }
    }
  }
```

---

### 단계 8) drain 타이머 + 명령 재전송 타이머
수신 큐는 짧은 주기로 돌리고,
명령은 마지막 값을 주기적으로 업데이트합니다.

```cpp
    using namespace std::chrono_literals;
    rx_timer_ = create_wall_timer(1ms, [this]() { drainDriverQueue(); });

    if (command_refresh_hz_ > 0.0) {
      const auto period = std::chrono::duration_cast<std::chrono::nanoseconds>(
          std::chrono::duration<double>(1.0 / command_refresh_hz_));
      cmd_timer_ = create_wall_timer(period, [this]() {
        if (!last_cmd_received_.has_value()) return;
        driver_.setCommand(last_cmd_v_, last_cmd_w_);
      });
    }
```

---

### 단계 9) main 함수

```cpp
int main(int argc, char** argv) {
  rclcpp::init(argc, argv);
  try {
    auto node = std::make_shared<KmcHardwareDriverObserveNode>();
    rclcpp::spin(node);
  } catch (const std::exception& e) {
    RCLCPP_ERROR(rclcpp::get_logger("kmc_hardware_driver_observe_node"), "Fatal: %s",
                 e.what());
  }
  rclcpp::shutdown();
  return 0;
}
```

---

## Result
`examples/Driver_ROS2/src/driver_observe_node.cpp`

```cpp
#include "KMC_driver.hpp"

#include <rclcpp/rclcpp.hpp>
#include <geometry_msgs/msg/twist.hpp>
#include <std_msgs/msg/float32.hpp>

#include <chrono>
#include <optional>
#include <string>

class KmcHardwareDriverObserveNode final : public rclcpp::Node {
public:
  KmcHardwareDriverObserveNode() : Node("kmc_hardware_driver_observe_node") {
    port_ = declare_parameter<std::string>("port", "/dev/ttyKMC");
    baud_ = declare_parameter<int>("baud", 921600);
    control_rate_hz_ = declare_parameter<double>("control_rate_hz", 100.0);
    vehicle_speed_rate_hz_ = declare_parameter<double>("vehicle_speed_rate_hz", 50.0);
    command_timeout_ms_ = declare_parameter<int>("command_timeout_ms", 200);
    command_refresh_hz_ = declare_parameter<double>("command_refresh_hz", 50.0);
    realtime_priority_ = declare_parameter<int>("realtime_priority", -1);
    cpu_affinity_ = declare_parameter<int>("cpu_affinity", -1);
    battery_hz_ = declare_parameter<double>("battery_hz", 1.0);

    KMC_HARDWARE::Driver::Options opt;
    opt.port = port_;
    opt.serial.baudrate = baud_;
    opt.serial.hw_flow_control = true;
    opt.control_rate_hz = control_rate_hz_;
    opt.vehicle_speed_rate_hz = vehicle_speed_rate_hz_;
    opt.command_timeout_ms = command_timeout_ms_;
    opt.realtime_priority = realtime_priority_;
    opt.cpu_affinity = cpu_affinity_;

    opt.poll_battery = battery_hz_ > 0.0;
    opt.battery_rate_hz = battery_hz_ > 0.0 ? battery_hz_ : 1.0;

    if (!driver_.start(opt)) {
      throw std::runtime_error("Failed to open UART port: " + port_);
    }

    speed_pub_ = create_publisher<std_msgs::msg::Float32>("vehicle_speed", 10);
    battery_pub_ = create_publisher<std_msgs::msg::Float32>("battery_voltage", 10);

    cmd_sub_ = create_subscription<geometry_msgs::msg::Twist>(
        "cmd_vel", 10, [this](geometry_msgs::msg::Twist::SharedPtr msg) {
          const float v = static_cast<float>(msg->linear.x);
          const float w = static_cast<float>(msg->angular.z);
          last_cmd_v_ = v;
          last_cmd_w_ = w;
          last_cmd_received_ = now();
          driver_.setCommand(v, w);
        });

    using namespace std::chrono_literals;
    rx_timer_ = create_wall_timer(1ms, [this]() { drainDriverQueue(); });

    if (command_refresh_hz_ > 0.0) {
      const auto period = std::chrono::duration_cast<std::chrono::nanoseconds>(
          std::chrono::duration<double>(1.0 / command_refresh_hz_));
      cmd_timer_ = create_wall_timer(period, [this]() {
        if (!last_cmd_received_.has_value()) return;
        driver_.setCommand(last_cmd_v_, last_cmd_w_);
      });
    }
  }

  ~KmcHardwareDriverObserveNode() override { driver_.stop(); }

private:
  void drainDriverQueue() {
    for (int i = 0; i < 100; ++i) {
      auto msg = driver_.tryPopMessage();
      if (!msg) break;

      if (auto* vs = std::get_if<KMC_HARDWARE::VehicleSpeed>(&*msg)) {
        std_msgs::msg::Float32 out;
        out.data = vs->mps;
        speed_pub_->publish(out);
      } else if (auto* bv = std::get_if<KMC_HARDWARE::BatteryVoltage>(&*msg)) {
        std_msgs::msg::Float32 out;
        out.data = bv->volt;
        battery_pub_->publish(out);
      }
    }
  }

private:
  KMC_HARDWARE::Driver driver_;

  rclcpp::Publisher<std_msgs::msg::Float32>::SharedPtr speed_pub_;
  rclcpp::Publisher<std_msgs::msg::Float32>::SharedPtr battery_pub_;
  rclcpp::Subscription<geometry_msgs::msg::Twist>::SharedPtr cmd_sub_;
  rclcpp::TimerBase::SharedPtr rx_timer_;
  rclcpp::TimerBase::SharedPtr cmd_timer_;

  std::string port_;
  int baud_{921600};
  double control_rate_hz_{100.0};
  double vehicle_speed_rate_hz_{50.0};
  int command_timeout_ms_{200};
  double command_refresh_hz_{50.0};
  int realtime_priority_{-1};
  int cpu_affinity_{-1};
  double battery_hz_{1.0};
  float last_cmd_v_{0.0f};
  float last_cmd_w_{0.0f};
  std::optional<rclcpp::Time> last_cmd_received_;
};

int main(int argc, char** argv) {
  rclcpp::init(argc, argv);
  try {
    auto node = std::make_shared<KmcHardwareDriverObserveNode>();
    rclcpp::spin(node);
  } catch (const std::exception& e) {
    RCLCPP_ERROR(rclcpp::get_logger("kmc_hardware_driver_observe_node"), "Fatal: %s",
                 e.what());
  }
  rclcpp::shutdown();
  return 0;
}
```