Qt - serial communication - receiving

[Christian Ehrlicher]

@Damian7546 said in Qt - serial communication - receiving:

How I should wait for all bytes in frame in my slot ?

You must not wait but read the data into a custom buffer (e.g. QByteArray) and parse the data later on.

[Damian7546]

So, I changed my slot "recive()" in this way:

void SerialWorker::recive()
{
        receivedData = receivedData + m_Serial->readAll();
        if(!receivedData.isEmpty())
        {
            timeoutReciveData(this, SLOT(parseRecivedData()), 1000);
        }
}

But something is wrong with singleshot , because doesn't work:

void SerialWorker::parseRecivedData()
{
     qDebug() << receivedData ;
         /* parse should be here */

}
void SerialWorker::timeoutReciveData(const QObject *obj, const char *signalOrSlot, int msDelay)
{
     QTimer::singleShot(msDelay, obj, signalOrSlot);
}

Any idea ?

[Christian Ehrlicher]

@Damian7546 said in Qt - serial communication - receiving:

But something is wrong with singleshot , because doesn't work:

does not work? What does this mean? Why do you not directly call parseRecivedData or QTimer::singleShot()?

[yinhao.qian]

This post is deleted!

[Damian7546]

@Christian-Ehrlicher said in Qt - serial communication - receiving:

Why do you not directly call parseRecivedData

Because I do not know when my frame will be completed, so I give the some time by timeoutReciveData and next go to parseRecivedData().
I expect such a frame:
DevAddres,LengthFrame,Command,Data1...n,CRCH,CRCL

@Christian-Ehrlicher said in Qt - serial communication - receiving:

does not work? What does this mean?

The parseRecivedData() slot does not start even though buffer "receivedData" are not empty .

[Christian Ehrlicher]

@Damian7546 said in Qt - serial communication - receiving:

Because I do not know when my frame will be completed, so I give the some time by timeoutReciveData and next go to parseRecivedData().

And why should it be finished in 1000ms? It does not help at all.
Parse your buffer directly.

[Damian7546]

Ok,
thank for your suggestion. I must rewrite my parseRecivedData() function.

[Damian7546]

I wrote again my "recive()" function like you said, it works, but I have several doubt.

void SerialWorker::recive()
{
        QByteArray buff2CalcChecksum;
        Frame *m_inFrame = nullptr;
        receivedData_raw = receivedData_raw + m_Serial->readAll();
        if(!receivedData_raw.isEmpty())
        {
            for(int i=0; i <  receivedData_raw.count(); i++)
            {
                buff2CalcChecksum = buff2CalcChecksum + receivedData_raw[i];
                if ((((m_inFrame->CalculateCRC2_in(buff2CalcChecksum)) & 0xFF) == buff2CalcChecksum[i+2])  &&
                    (((m_inFrame->CalculateCRC2_in(buff2CalcChecksum) >> 8) & 0xFF) == buff2CalcChecksum[i+1]))
                {
                    qDebug() << "We have the correct frame";
                    receivedData = receivedData_raw;
                    receivedData_raw.clear();
                    parseRecivedData();
                }

                if (receivedData_raw.count() > 20 ) receivedData_raw.clear();  /// it is not a good idea...
             }
         }
}

• How to protect code when too long no CRC sums ?

• It is a good idea that from first byte, calculate CRC sum to recognize my whole frame?

[Christian Ehrlicher]

I don't think your code will ever work - the data comes in as a stream so you first have to figure out the start and end of your frame. For this a lot of protocols use a start and end-marker so you know when a frame starts and ends.

[Damian7546]

This protocol do not have marker start and end of frame. This is a frame:

[Christian Ehrlicher]

Then I don't know how you will ever find the start of a frame... they must have at least e.g. an end marker ('\r' or '\n' for example) where you can start from.