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How to get uint8_t from a QByteArray



  • Hello,
    I have the following trouble: I have a QSerialPort that read the messages from a Pixhawk (a component that transmit messages in a Hexadecimal base, with values from 0 to 255). When I read the messages I store this datas in a QByteArray, that has the following apparence:
    0_1552741930079_Problema2Foto1.PNG

    At this point, I passed this QByteArray to other one with the command toHex and I get this QByteArray:
    0_1552741984416_Problema2Foto2.PNG

    But now I want to access to the byte of the original messages thought the last one QByteArray. I know that the information in the message is store in every two characters, so every byte is a number that has some kind of meaning that I can translate with a library called MavLink.
    However I dont know how to access to one byte from the last QByteArray, i can access to the chars and the I can append this char to a string and then get to value in a int though toInt. But with this method I have two troubles: its really heavy and, overall, in some time I will need to construct variables uint16_t or uint64_t and I dont know what to do to get it.

    
    int pasarNumeroaINT8 (QByteArray as, int i1){
        char prim=as.at(i1), sec=as.at(i1+1);
        QString byte = ""; byte.append(prim); byte.append(sec);
        bool ok;
       int byteInt = byte.toInt(&ok, 16);
    
       return byteInt;
    
    }
    

    I tried other method, and it was make it with the original QByteArray and a static cast, but I dont get values between 0 and 255, but -128 and 128.

    data = serial->readAll();
    
        dataAux = data.toHex();
    
         qDebug()<<static_cast<int8_t>(data[0]);
    

    Anyone can help me? Thanks you.

    Sorry for my English.


  • Lifetime Qt Champion

    @Dooham said in How to get uint8_t from a QByteArray:

    but -128 and 128.

    Because you cast to int8_t ...



  • @Christian-Ehrlicher Thanks, that was exactly my problem.


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