[Solved] QSerialPort close() throws Unknown error

[A Former User]

Hi,
Im talking with my GSM-Modem with QSerialPort.
At the beginning i do the following:
@QSerialPort* pSerialPort = new QSerialPort(this);@

I have a "start()" Funktion within i do this:

@pSerialPort->setPortName(sPortName);

if (pSerialPort->open(QIODevice::ReadWrite))
{
    if (pSerialPort->setBaudRate(QSerialPort::Baud19200)
            && pSerialPort->setDataBits(QSerialPort::Data8)
            && pSerialPort->setParity(QSerialPort::NoParity)
            && pSerialPort->setStopBits(QSerialPort::OneStop)
            && pSerialPort->setFlowControl(QSerialPort::NoFlowControl))
    {
        connect(pSerialPort, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(serialPortError(QSerialPort::SerialPortError)));
        connect(pSerialPort, SIGNAL(readyRead()), this, SLOT(serialRead()));
        stateMaschine(START);
        emit info("GsmCommunication::start(): COM-Schnittstelle erfolgreich initialisiert", GlobalVars::SI_COM_PORT_INIT_OK);
        pSmsCheckTimer->start();

    }
    else
    {
        emit error("GsmCommunication::start(): Kann COM-Schnittstelle nicht initialisieren");
    }
}
else
{
    emit error("GsmCommunication::start(): Kann COM-Schnittstelle nicht oeffnen");
}@

I have a "stop()"-function within i do this:

@pSerialPort->clear();
pSerialPort->close();@

And i have a reInit()-function, within i do this:

@stop();
start();@

Everything works fine, but i get "Unknown error" from QSerialPort when i call my reInit()-Function. Seems like QSerialPort.close() causes the error, why is that?

[kuzulis]

1. Can you try it with the Terminal example (from the QtSerialPort package)?
   I mean just do clicks to the "connect" and "disconnect" buttons.

2. What OS is used?

3. What model of modem is used (what is device)?

4. What version of QSerialPort you use? From the Git?

5. The QObject::connect should be done once after creation of the QSerialPort's object, like:

@
QSerialPort* pSerialPort = new QSerialPort(this);

connect(pSerialPort, SIGNAL(error(QSerialPort::SerialPortError)),
this, SLOT(serialPortError(QSerialPort::SerialPortError)));

connect(pSerialPort, SIGNAL(readyRead()), this, SLOT(serialRead()));
@

[A Former User]

Ty for ur answer,
I tried it with the terminal example, i added the following code to see any kind of errors:

@void MainWindow::handleError(QSerialPort::SerialPortError error)
{
qDebug() << "ERROR: " << error; //I added this line
if (error == QSerialPort::ResourceError) {
QMessageBox::critical(this, tr("Critical Error"), serial->errorString());
closeSerialPort();
}
}@
Since then also the terminal-example shows "ERROR: 0", but not as I thought when close() is called, it appears when I click the "connect" button, also in my Program it appears in my start() function. I added "pSerialPort->clear()" just before "open()" is called, since then i get the following Error-String:
"Das Handle ist ungültig." Which i would translate in english as "The Handle is not valid". Without the clear() its "Unknown Error".

The OS is Microsoft Windows 7 32bit.
The Device is a CT63 GSM-Modem conneted with a USB->RS232 connector.
I use the build in Version of QSerialPort in QT 5.1.1
(#include <QtSerialPort/QSerialPort>)
I fixed the issue of wrong placed connect(), but that doesnt appear to make any changes.

[kuzulis]

bq. Since then also the terminal-example shows “ERROR: 0”

It is NoError.

bq. “pSerialPort->clear()” just before “open()” is called, since then i get the following Error-String

It is because your port already closed, so the clear() method can't to be success.

bq. USB->RS232 connector

What is connector model?

bq. I use the build in Version of QSerialPort in QT 5.1.1

Please download and compile the Git version of QtSerialPort and try check again.

Also:

1. Please provide a minimal compilable project that reproduce a problem (it is better - console if possible).

2. You can try to do debugging himself to help us.

[A Former User]

I changed my Modification in the terminal example:

@void MainWindow::handleError(QSerialPort::SerialPortError error)
{
qDebug() << "ERROR: " << error << "ErrorString: " << serial->errorString();
if (error == QSerialPort::ResourceError) {
QMessageBox::critical(this, tr("Critical Error"), serial->errorString());
closeSerialPort();
}
}@
Now the terminal example shows the following in debugging console:
*ERROR: 0 ErrorString: "Unknown error" *
Thats exactly the same behaivior as in my Program.

The USB->RS232 converter is type U232-P9 made in Taiwan (-: dont have more information.

I will have to read about the Git Version and how to compile it, never heard about that so far.

[kuzulis]

bq. *ERROR: 0 ErrorString: “Unknown error”

This is not an error. Just ignore/skip SerialPortError::NoError error code.. :)