Reading from Arduino using QSerialPort stops after a few bytes

[FlyingDude]

Hi,

I am trying to receive bytes from an Arduino's (emulated USB) serial port using QSerialPort.

Currently I simply send an incrementing / overflowing single byte on the arduno side:

void loop() {
static unsigned char cnt = 0;
cnt++;
Serial.write(&cnt, 1);
}

When I connect to the emulated COM-port using putty, I receive an endless stream of bytes, as expected.

However, when I try to achieve the same using QSerialPort, the Arduino sends for a short time (TX led is active), I receive a batch of bytes in one go but then the TX led stays dark and I don't receive any more data.

port.setPortName("COM23");
if (!port.open(QIODevice::ReadWrite)) {
printf("Error opening serial: %d\n", port.error());
}

if(!port.setParity(QSerialPort::NoParity) ||
    !port.setStopBits(QSerialPort::OneStop) ||
    !port.setDataBits(QSerialPort::Data8) ||
    !port.setFlowControl(QSerialPort::NoFlowControl ) ||
    !port.setBaudRate(115200))
 {
    qFatal("Unable to configure serial port");
    exit(1);
 }

char ackStatus = 0;
while(1) {
    int bytesRead = port.read(&ackStatus, 1);

    if(bytesRead > 0) {
      printf("Data received, length: %d, val: %d\n", bytesRead, ackStatus);
      fflush(stdout);
    }else {
      qApp->processEvents(QEventLoop::ExcludeUserInputEvents);
    }
}

Any idea what the difference between putty and QSerialPort might be in this case?

Thank you in advance, Clemens

[mrjj]

Hi could you try the "Terminal sample"
and see if it has same behavior?

[FlyingDude]

I figured out, it was nescessary to set DTR:

port.setDataTerminalReady(true);

Thanks & br, Clemens