c++ - 错误 5 : Access is Denied when using WriteFile to interface Arduino and C++ program

Question

我正在开发一个 C++ 控制台程序来连接 Arduino Uno。我需要向 Arduino 板发送一个 key ，以便它可以激活 RFID 传感器并将读取的 UID 发送回程序。

ReadFile 函数工作得~几乎~完美，但是当我尝试向 Arduino 发送一个“a”以便它可以开始运行它的 ReadFromRFID 函数时，我收到了这条消息:

"Error 5: Access is Denied"

有谁知道我做错了什么以及如何做对？

这是我目前的代码:

HANDLE hSerial;

void printErro() {

    printf(":: ERRO ::\n");

    wchar_t erro[1024];
    FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM, NULL, GetLastError(),
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), erro, 1024, NULL);
    printf("Erro %ld: %ls", GetLastError(), erro);

}

HANDLE conectArduino() {

    LPCWSTR porta = L"COM3";

    hSerial = CreateFile(porta, GENERIC_READ, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

    if (hSerial == INVALID_HANDLE_VALUE){
        if (GetLastError() == ERROR_FILE_NOT_FOUND){

            printErro();

        }
        //some other error occurred. Inform user.

        printErro();

    }

    DCB parametros = { 0 };
    parametros.DCBlength = sizeof(parametros);
    parametros.BaudRate = CBR_9600;
    parametros.ByteSize = 8;
    parametros.StopBits = ONESTOPBIT;
    parametros.Parity = NOPARITY;

    if (!SetCommState(hSerial, &parametros)){
        //error setting serial port state

        printErro();

    }

    COMMTIMEOUTS timeouts = { 0 };
    timeouts.ReadIntervalTimeout = 10000;
    timeouts.ReadTotalTimeoutConstant = 1000;
    timeouts.ReadTotalTimeoutMultiplier = 0;
    timeouts.WriteTotalTimeoutConstant = 100;
    timeouts.WriteTotalTimeoutMultiplier = 0;

    if (!SetCommTimeouts(hSerial, &timeouts)) {

        printErro();

    }

    return hSerial;

}

void readArduino(HANDLE hSerial) {

    printf("RECEBENDO DADOS DO ARDUINO\n\n");

    char buffer[12] = { 0 };
    DWORD qtdBytesLida = 0;

    if (!ReadFile(hSerial, buffer, 11, &qtdBytesLida, NULL)) {

        printErro();

    }

    printf("%d: %*.*s", qtdBytesLida, qtdBytesLida, qtdBytesLida, buffer);

    getchar();

    printf("\n\n");
    printf("----------------------------------------------------------------------");
    printf("\n\n");

}

void sendArduino(const char* palavra) {

    printf("ENVIANDO DADOS PARA O ARDUINO\n\n");

    char buffer[2] = "a";
    DWORD qtdBytesEscrita = 0;

    HANDLE hSerial = conectArduino();

    if (!WriteFile(hSerial, buffer, 1, &qtdBytesEscrita, NULL)) {

        printErro();

    }
    else {

        readArduino(hSerial);

    }

    CloseHandle(hSerial);

    getchar();

    printf("\n\n");
    printf("----------------------------------------------------------------------");
    printf("\n\n");

}

Answer 1

您只使用 GENERIC_READ 打开串行端口，这意味着只读访问。如果您希望能够写入，您还需要添加 GENERIC_WRITE。

hSerial = CreateFile(porta, GENERIC_READ | GENERIC_WRITE, 0, 0,
    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);