QSerialPort random read timeout

[theknight47]

Hello everyone,

I have a very strange problem with the QSerialPort::waitForReadyRead method, I use the following code ( running on a thread ):

@String portCom::sendRequest( QString request )
{
serial->clear();
serial->write( request.toLocal8Bit() );

if (serial->waitForBytesWritten( 10000 )) {

 QByteArray responseData;
        if (serial->waitForReadyRead( 10000 )) {

            qint64 av = serial->bytesAvailable();
std::cout << "Bytes to write " << av << std::endl;

QByteArray oneResponse;

 while ( serial->waitForReadyRead( 100 ) )
 { 
  oneResponse = serial->readAll();

  for ( int i=0; i < oneResponse.size(); i++ )
  {
   if ( QString( oneResponse.at(i) ) == "!" ) break;
   else 

   { 
    responseData +=  oneResponse.at(i);
    qDebug ( QString( oneResponse.at(i) ).toLatin1() );
   }
   
  }
  
  
 }
//}

            QString response2( responseData );

response2.remove( "\n" );

return response2;

        } else {

std::cout << "error code AR003 : Wait read response timeout " << std::endl; 
std::cout << serial->errorString().toStdString() << std::endl;

serial->clear();
//serial->clear();
serial->close();

if ( serial->open( QIODevice::ReadWrite ) ) 
{
 std::cout << "Serial reopened" << std::endl;
}

else 
{
 std::cout << "failed to open the device" << std::endl;
}


return QString("AR_ERROR");
        }
       
    } else {

std::cout << "error code AR002 : Wait write request timeout " << std::endl;

serial->clear();
serial->close();

if ( serial->open( QIODevice::ReadWrite ) ) 
{
 std::cout << "Serial reopened" << std::endl;
}

else 
{
 std::cout << "failed to open the device" << std::endl;
}

return QString("AR_ERROR");
}

}
@

Actually, the communication with the COM port (Arduino Uno) is working fine but in some times I have a read timeout and after that no response ( only read/write timeouts )

My question is : can this problem be relative to the Qt functions (waitForReadyRead / waitForBytesWritten ) or is a hardware issue that can occur on the device.

Thank you very much

[BowCatShot]

If you're running on a Linux system, try doing a google search on EAGAIN. It's a known Linux bug and may pertain to what's going on here.

[theknight47]

Thank you BowCatShot for the reply

Actually, I am working on Windows 8.1 plate form with Qt 5.2.1

Thank you very much