Hey, I'm experiencing a very weird and annoying problem. While I record the data and I minimize or maximize the SW window I got corrupted data. BUT, If I first open the RealTerm and then open / close the port and then starting to record data with my SW then the problem is gone. P.S. it's happened in high rate - 400hz. Any suggestions? port = new QextSerialPort(portName,QextSerialPort::EventDriven); if(!port->open(QIODevice::ReadOnly )) return -1; connect( port, SIGNAL(readyRead()), this, SLOT(onReadyRead())); port->setBaudRate(BAUD691200); port->setDataBits(DATA_8); port->setParity(PAR_NONE); port->setStopBits(STOP_1); port->setFlowControl (FLOW_OFF); port->setRts( true ); port->setDtr( true ); My setup: Windows xp sp3 Serial port RS-422 BaudRate : 691200 Qt 4.7.0 Qextserialport 1.2 beata2.