QSerialPort is(n't) sending data to ESP8266

Gh0stShell

Hi,

this is my first time I work with QSerialPort and I try to send data to an ESP8266. I tried the tool "Serial Port Monitor" to make a test message to the ESP and the connection is working so the problem shouldn't be on the ESP's side.

QSerialPort serialo;

        Q_FOREACH(QSerialPortInfo port, QSerialPortInfo::availablePorts()) {

            if (port.description().compare("Silicon Labs CP210x USB to UART Bridge") == 0) {
                serialo.setPort(port);
                qDebug() << serialo.portName();
                serialo.setBaudRate(QSerialPort::Baud9600);
                serialo.setDataBits(QSerialPort::Data8);
                serialo.setParity(QSerialPort::NoParity);
                serialo.setStopBits(QSerialPort::OneStop);
                serialo.setFlowControl(QSerialPort::NoFlowControl);
                qDebug() << "PortOpen: " << serialo.open(QIODevice::ReadWrite);
                qDebug() << "BytesSend: " << serialo.write("test");

                serialo.close();

            }
        }

I wrote this. Qt can open the port and it sends 4 Bytes, but the ESP isn't getting anything.

Am I doing something completely wrong over there? Or is it something like a known issue or something?

Edit: The ESP is connected via USB

kuzulis

You close the serial port before that the write starts. QSP::write() does not write the data immediatelly, it starts writing when the QSP becomes ready to write, internally.

Gh0stShell

Oh, ok. Is there a function to wait for writing is done?

J.Hilk

@Gh0stShell said in QSerialPort is(n't) sending data to ESP8266:

Oh, ok. Is there a function to wait for writing is done?

yes, but rather use the BytesWritten signal.

kuzulis

@Gh0stShell said in QSerialPort is(n't) sending data to ESP8266:

Oh, ok. Is there a function to wait for writing is done?

Yes, you can use QSP::waitForBytesWritten(), but it is a very bad design. You should create your serial port instance on a heap and to use the signals/slots instead, as @J-Hilk suggested.

Gh0stShell

Thank you, the problem was, that I didn't wait for the Bytes to be written.