1

我正在编写一个 C++ 程序来与多个设备进行通信——一个带有 ATmega328 的 Arduino Pro Mini 和一个带有 GPS 屏蔽的 Arduino Uno——同时通过 COM 端口，我正在使用 boost::asio 包。我不是 C++ 大师，所以我偶尔会搞不清楚在哪里/何时通过引用或值传递；我认为这是其中一种情况。

这是设置用于通信的串行端口的代码

std::string IMU_COM_PORT = "COM5"; // or whatever... it varies
int IMU_BAUD_RATE = 57600;
std::string ARDUINO_COM_PORT = "COM3"; // also varies
int ARDUINO_BAUD_RATE = 115200;

int main() {
    std::vector<boost::thread *> sensorThreads;
    int sensorThreadCount = 0;

    using namespace::boost::asio;

    // get the COM port handle for the IMU sensor
    boost::asio::io_service IMU_io;
    boost::asio::serial_port IMU_port(IMU_io);
    IMU_port.open(IMU_COM_PORT);
    if (!IMU_port.is_open()) {
        cerr << "Failed to connect to IMU." << endl;
    }
    else {
        IMU_port.set_option(boost::asio::serial_port_base::baud_rate(IMU_BAUD_RATE));
        // the IMU has to be put into triggered output mode with a specific command: #o0
        // to put it back into continuous output mode we can use this command: #o1
        std::string IMU_init_cmd = "#o0";
        boost::asio::write(IMU_port, boost::asio::buffer(IMU_init_cmd.c_str(), IMU_init_cmd.size()));
        // now the IMU should be ready

        sensorThreads.push_back(new boost::thread(testIMUThread, IMU_port));
        sensorThreadCount++;
    }

    // get the COM port handle for the ARDUINO board with GPS sensor
    boost::asio::io_service ARDUINO_io;
    boost::asio::serial_port ARDUINO_port(ARDUINO_io);
    ARDUINO_port.open(ARDUINO_COM_PORT);
    if (!ARDUINO_port.is_open()) {
        cerr << "Failed to connect to ARDUINO." << endl;
    }
    else {
        ARDUINO_port.set_option(boost::asio::serial_port_base::baud_rate(ARDUINO_BAUD_RATE));
        // now the ARDUINO w/GPS sensor should be ready

        sensorThreads.push_back(new boost::thread(testGPSThread, ARDUINO_port));
        sensorThreadCount++;
    }

    for (int i = 0; i < sensorThreadCount; i++) {
        sensorThreads[i]->join();
        delete sensorThreads[i];
    }
}

我的两个测试线程函数基本相同，唯一的区别是它们发送到设备的字节表明某些东西（我的计算机）正在等待从它们读取数据。

void testIMUThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

并且这两个测试线程都使用一个执行串行读/写的函数。

std::string readCOMLine(boost::asio::serial_port *port, std::string requestDataCmd) {
    char c;
    std::string s;
    boost::asio::write(port, boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size()));
    while(true) {
        boost::asio::read(port, boost::asio::buffer(&c,1));
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}

上面的代码不会编译，而是产生以下内容（在 MSVC2010 中）： Error 11 error C2248: 'boost::asio::basic_io_object<IoObjectService>::basic_io_object' : cannot access private member declared in class 'boost::asio::basic_io_object<IoObjectService>' C:\boost_1_51_0\boost\asio\basic_serial_port.hpp

错误消息是相当无用的 - 至少对我来说 - 因为我无法找到根本原因。我在这里想念什么？

谢谢你的帮助。

编辑：解决方案（感谢 Sam Miller）

使用传递引用（即boost::ref()）

sensorThreads.push_back(new boost::thread(testIMUThread, IMU_port));
sensorThreads.push_back(new boost::thread(testIMUThread, ARDUINO_port));

在main()成为

sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(IMU_port)));
sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(ARDUINO_port)));

然后主力和线程函数被修改为这样

std::string readCOMLine(boost::asio::serial_port &port, std::string requestDataCmd) {
    char c;
    std::string s;
    boost::asio::write(port, boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size()));
    while(true) {
        boost::asio::read(port, boost::asio::buffer(&c,1));
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}
void testIMUThread(boost::asio::serial_port &port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port &port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

另一方面，如果使用 pass-by-pointer，线程初始化main()看起来像这样

sensorThreads.push_back(new boost::thread(testIMUThread, &IMU_port));
sensorThreads.push_back(new boost::thread(testIMUThread, &ARDUINO_port));

和这样的线程功能

void testIMUThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

但是我必须对完成所有工作的函数（即读/写调用）进行一些额外的更改（在修改输入参数的基础上）。

std::string readCOMLine(boost::asio::serial_port *port, std::string requestDataCmd) {
    char c;
    std::string s;
    port->write_some(boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size())); // this line
    while(true) {
        port->read_some(boost::asio::buffer(&c,1)); // and this line
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}

两种解决方案都可以编译并且似乎可以满足我的目的。

谢谢！

4

1 回答 1

1

boost::asio::serial_port对象是不可复制的

你应该通过参考

sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(IMU_port)));

或指针

sensorThreads.push_back(new boost::thread(testIMUThread, &IMU_port));

这是一个显示两种方法的大肠杆菌。

于 2013-04-26T16:27:22.903 回答