QSerialPort - OpenError [solved]

[don_kon]

Hello everyone,

I'm trying to use the QSerialPort to send data to a FTDI and read the data that comes back. I'm fairly new in coding, so I tried to get all the information from the examples and other posts, but nothing really helped. So my problem is that I cannot open the port and the error code that I get is number 3 OpenError what means that the port is already open?? I made sure that no other program uses the port e.g. Terminal. But still I can't open it.

meinlayout::meinlayout(QWidget *parent)
    : QMainWindow(parent)
{
    serial = new QSerialPort(this);
    //info = new QSerialPortInfo();

    foreach (const QSerialPortInfo &info, QSerialPortInfo::availablePorts())
    {
    qDebug() << "Available Ports: " << info.portName();
    }

    serial->setPortName("COM3");

    if(serial->portName()!= "COM3")
    {
        qDebug() << tr("error set name %1").arg(serial->error()) << serial->portName();
        return;
    }
    serial->setBaudRate(QSerialPort::Baud115200);

    if(serial->baudRate()!= 115200)
    {
        qDebug() << tr("error set Baud %1").arg(serial->error());
        return;
    }

    serial->setDataBits(QSerialPort::Data8);

    if(serial->dataBits()!= 8)
    {
        qDebug() << tr("error set bits %1").arg(serial->error());
        return;
    }

    serial->setParity(QSerialPort::NoParity);

    if(serial->parity()!= 0)
    {
        qDebug() << tr("error set parity %1").arg(serial->error());
        return;
    }

    serial->setFlowControl(QSerialPort::NoFlowControl);

    if(serial->flowControl()!= 0)
    {
        qDebug() << tr("error set flow %1").arg(serial->error());
        return;
    }

    serial->setStopBits(QSerialPort::OneStop);

    if(serial->stopBits()!= 1)
    {
        qDebug() << tr("error set stop %1").arg(serial->error());
        return;
    }

    if(serial->isOpen())
    {
        qDebug() << "Port already opened!";
        serial->close();
    }


   serial->open(QIODevice::ReadWrite);


    if(!serial->open(QIODevice::ReadWrite))
    {
        qDebug() << tr("error open Port %1").arg(serial->error());
        return;
    }

}

meinlayout::~meinlayout()
{
    serial->close();
}

so the output I get is:

Available Ports: "COM3"
"error open Port 3"

any suggestions what I'm doing wrong?

[jsulm]

@don_kon said in QSerialPort - OpenError:

serial->open(QIODevice::ReadWrite);

if(!serial->open(QIODevice::ReadWrite)

Why do you open it twice?!

[don_kon]

@jsulm Thank you for your help, after I annotated the first open() the program worked.
I didn't know the

if(!serial->open(QIODevice::ReadWrite))

will try to open the port again.

[jsulm]

@don_kon said in QSerialPort - OpenError [solved]:

will try to open the port again

I don't think it will try to open it again, but if it is already open it will return false.

[don_kon]

@jsulm Thanks!