Question

我正在用Qt和arduino制作RPM计数器GUI，我正在使用冷却乐趣来获取RPM值。我正在使用串口从arduino读取值，但有时我会错过我在Qt GUI中打印的值的最后一个字节，但我在arduino串行监视器中没有相同的问题。以下是Qt的代码：

void ArduinoRpm::serialReciver()
{

    QString input_converter;
    std::string to_file_string;

    int sizeFromInput = 0;
    char *dataBuffer;

    //get the port size depending on bytes available to read
    int bufferSize = serial->bytesAvailable();
    //int bufferSize = serial->bytesAvailable();

    //dataBuffer, get the data from serial port, bufferSize + 1 for the newline
    dataBuffer = new char[bufferSize + 2];

    //flush the port before read


    //This function reads a line of ASCII characters from the device, up to a maximum of
    //maxSize - 1 bytes, stores the characters in dataBuffer, and returns the number of bytes
    //read. if a line could not be read but no error ocurred, this function returns 0. if an
    //error occurs, this function returns the length of what could read or -1 if nothing was read.
    //bufferSize is the maxsize readline can read.

    sizeFromInput = serial->readLine(dataBuffer, bufferSize);

    //to_file_string, to write data in file
    to_file_string = dataBuffer;
    input_converter = QString::fromStdString(to_file_string);


    if ((sizeFromInput >= 1) && (input_converter.toInt() <= 9999)) {
        if(input_converter.toInt() > 10) {
            ui->lcdNumber->display(input_converter);
            rpmNeedle->setCurrentValue(input_converter.toInt());
            input_file << to_file_string << std::endl;
        }

    }

    delete dataBuffer;
    bufferSize = 0;
    serial->flush();

}

 void ArduinoRpm::SerialInitializer()
{
    serial = new QSerialPort(this);
    serial->setPortName(serialPortValue); //COM-port your Arduino is connected to
    serial->open(QIODevice::ReadWrite);
    serial->setBaudRate(QSerialPort::Baud9600); //must be the same as your arduino-baudrate
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
}

例如

它应该一直读取4位数，但有时会丢失最后一位数字。对此有何解决方案？

Answer 1

你的功能应该是这样的：

void ArduinoRpm::serialReciver()
{
    char dataBuffer[6];

    if(!serial->canReadLine()) //if there isn't a whole line available
        return; //return from this call (wait for the next readyRead() signal)
    serial->readLine(dataBuffer, 6)

    /* do whatever you want with dataBuffer here */

    if(serial->bytesAvailable() > 0) //if there are still unread bytes
        QMetaObject::invokeMethod(this, "serialReciver", Qt::QueuedConnection); //call function again as if readyRead() signal was emitted
}

P.S这个答案假定输入保证总是这样：4个数字字符然后换行，然后是4个数字字符，然后再换行，等等。。因此，如果它不遵循这种模式，那么这将导致未定义的行为。

P.S我没有在 serialReciver 中解决您的拼写错误。

Qt串口有时会丢失最后一个字节

1 个答案: