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Reading continuous data from Serial Port



  • Hi friends,
    I am new for QT C++ and am trying to write a program, which could continuous read data from Serial Port. My Program works sometimes smoothly but sometimes it read wrong data. I have run debug and here is what I got:

    "61\x00\x00"
    "61\x00\x00"
    "61\x00\x00"
    "62\x00\x00"
    "62\x00\x00"
    "62\x00\x00"
    "62\x00\x00"
    "63\x00\x00"
    "63\x00\x00"
    "5"
    "3\x00\x00"
    "5"
    "2\x00\x00"
    "5"
    "2\x00\x00"
    
    "54\x00\x00"
    "54\x00\x00"
    "54\x00\x00"
    "55\x00\x00"
    "54\x00\x00"
    "54\x00\x00"
    "55\x00\x00"
    "55\x00\x00"
    "5"
    "1\x00\x00"
    "51"
    "\x00\x00"
    "5"
    "2\x00\x00"
    "5"
    "1\x00\x00"
    "5"
    "1\x00\x00"
    

    Someway QTSerialPort didn't read all data. And here is my code, where data should be read and display.

       if(serial->isOpen() && serial->isReadable()){
           QByteArray receivedData;
           receivedData = serial->readAll();
           qDebug()<<receivedData;
           ui->lcdDistance->display(receivedData.toInt());
        }else{
           QMessageBox::critical(this, tr("Error"), tr("Doesn't receive data"));
        }
    

    I think the problem came from QT, not the microcontroller because I also run debug with my microcontroller and it worked very well.

    Please help me to solve this problem. Thanks in advance.


  • Lifetime Qt Champion

    QSerialPort is async - connect to the readyRead() signal and read the data data. What you do here can't work since readAll() is non-blocking (and that's fine)



  • I used readyRead() for the very first time but it still happened

     connect(serial, SIGNAL(readyRead()), this, SLOT(serialReceived()));
    

  • Lifetime Qt Champion

    Hi,

    Serial port data are not guaranteed to arrive as full frames.

    You should cumulate the data you get and then check if a full frame can be found in that buffer, process it and then go on.


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