QSerialPort & QDataStream - Data not sent to the Serial Device

Kevin470

Hello,
I am new to Qt and I am trying to read and write to a Serial Device using QSerialPort with Qt6.
I need to send three bytes of data for my device to respond.
Hterm was used to test if it successfully receives Hex data and it also gives a valid response.

I tried sending the same using QSerialPort. The port opens and closes successfully, but no write shown in the com port sniffer.

I am unable to find where I am making a mistake.
Any help would be amazing.

The code I run to send those three bytes is here

if (m_serialPort.isOpen()) {
        qDebug() << "Serial port is open...";
        Sleep(1000);

QByteArray buffer;
    QDataStream stream(&buffer, QIODevice::WriteOnly);

    stream << START_BYTE; //0x02
    stream << GET_TEMP;   //0x74  
    stream << LAST_BYTE;  //0x03

    qInfo() << buffer;
    qInfo() << "Buffer length:"<< buffer.length();

    if(m_serialPort.isWritable())
    {
      qInfo() <<  m_serialPort.write(buffer,buffer.length());

    } else {

            qInfo() << "Not Writable";
        }

        Sleep(6000);
        m_serialPort.close();
        qDebug() << "...serial port is closed!";

(qInfo() << buffer) gives "\x02t\x03" as output

Edit - Added QDataStream in title.

Christian Ehrlicher

@Kevin470 said in QSerialPort & QDataStream - Data not sent to the Serial Device:

 Sleep(6000);

Don't do this... To make sure the buffer is flushed you should use... QSerialPort::flush()

Kevin470

@Christian-Ehrlicher Yup, it worked! Thanks a lot.