Reading continuous data from Serial Port

StayCool

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.

Christian Ehrlicher

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)

StayCool

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

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

SGaist

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.