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Serial data received

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qt c++serialportdatabuffer
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  • JonBJ JonB

    @manel-sam said in Serial data received:

    however I also receive data of 0 bytes, which are empty and this quite frequently

    • If you only call readAll() once in response to each readRead() signal you will never get 0 bytes.
    • If you get 0 bytes you are calling readAll() a second time/not in response to readyRead(). Find out where, and don't do it.

    I would like to receive each time the data in full form

    You cannot guarantee you will receive all bytes on any one particular readAll() call. Like @J-Hilk said you need to write code to accumulate the (potentially fragments) of data you receive.

    M Offline
    M Offline
    manel.sam
    wrote on last edited by
    #10

    Imu::~Imu()
    {
    serialPort->close();
    }

    void Imu::handleError(QSerialPort::SerialPortError error)
    {
    if (error == QSerialPort::ResourceError){
    qDebug()<<"Handle Error"<<error;
    serialPort->close();
    }
    }

    void Imu::pollSerialPort()
    {

     QByteArray d= serialPort->readAll().toHex();
    
       QByteArray hexData = d.append(serialPort->readAll().toHex());
    
    qDebug() << "Serial received " << hexData;
    

    i used it like this

    JonBJ 1 Reply Last reply
    0
    • M manel.sam

      Imu::~Imu()
      {
      serialPort->close();
      }

      void Imu::handleError(QSerialPort::SerialPortError error)
      {
      if (error == QSerialPort::ResourceError){
      qDebug()<<"Handle Error"<<error;
      serialPort->close();
      }
      }

      void Imu::pollSerialPort()
      {

       QByteArray d= serialPort->readAll().toHex();
      
         QByteArray hexData = d.append(serialPort->readAll().toHex());
      
      qDebug() << "Serial received " << hexData;
      

      i used it like this

      JonBJ Offline
      JonBJ Offline
      JonB
      wrote on last edited by JonB
      #11

      @manel-sam
      This is wrong because you have two calls to serialPort->readAll(). How many more times can I say you cannot afford to do this? [In fact you kind of get away with this the way you write, but why are you calling it twice??]

      M 1 Reply Last reply
      2
      • JonBJ JonB

        @manel-sam
        This is wrong because you have two calls to serialPort->readAll(). How many more times can I say you cannot afford to do this? [In fact you kind of get away with this the way you write, but why are you calling it twice??]

        M Offline
        M Offline
        manel.sam
        wrote on last edited by
        #12

        @JonB Sorry, I copied the wrong code

        I used the readAll once, but I still get the 0 Bytes

        J.HilkJ JonBJ 2 Replies Last reply
        0
        • M manel.sam

          @JonB Sorry, I copied the wrong code

          I used the readAll once, but I still get the 0 Bytes

          J.HilkJ Offline
          J.HilkJ Offline
          J.Hilk
          Moderators
          wrote on last edited by
          #13

          @manel-sam can you show more of your code, calling connect multiple times will lead to such a behaviour as well


          Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


          Q: What's that?
          A: It's blue light.
          Q: What does it do?
          A: It turns blue.

          M 1 Reply Last reply
          0
          • J.HilkJ J.Hilk

            @manel-sam can you show more of your code, calling connect multiple times will lead to such a behaviour as well

            M Offline
            M Offline
            manel.sam
            wrote on last edited by
            #14

            @J-Hilk

            Imu::Imu() :
            moving(false)
            {

            serialPort = new QSerialPort("COM3",this);
            
            if (serialPort->open( QIODevice::ReadWrite))
            {
            
                qDebug()<<"SerialPort"<<serialPort<<"Opened successufly";
            }
            else
            {
                qDebug()<<serialPort->error();
                QSerialPortInfo::availablePorts();
            }
            
            if (!serialPort->setBaudRate(57600))
                log_error("imu","failed to set baudrate, error no %d",serialPort->error());
            serialPort->setDataBits(QSerialPort::Data8);
            serialPort->setParity(QSerialPort::NoParity);
            serialPort->setStopBits(QSerialPort::OneStop); // One Stop bit
            serialPort->setFlowControl(QSerialPort::NoFlowControl);
            qDebug()<<"error"<<serialPort->errorString();
            
            QObject::connect(this->serialPort,SIGNAL(readyRead()),this,SLOT(pollSerialPort()));
            QObject::connect(serialPort, &::QSerialPort::errorOccurred,this,&Imu::handleError);
            
            }
            

            Imu::~Imu()
            {
            serialPort->close();
            }

            void Imu::handleError(QSerialPort::SerialPortError error)
            {
            if (error == QSerialPort::ResourceError){
            qDebug()<<"Handle Error"<<error;
            serialPort->close();
            }
            }

            void Imu::pollSerialPort()
            {

            QByteArray hexData;
            hexData.append(serialPort->readAll().toHex());
            
            qDebug() << "Serial received " << hexData;
            QByteArray data = QByteArray::fromHex(hexData);
            
            // data size
            qInfo() << QStringLiteral("data size is : ") << data.size() << " octets";
            
            QDataStream stream(data);
            
            // Read The BigIndian value
            stream.setByteOrder(QDataStream::BigEndian);
            qint16 headerSignature;
            stream >> headerSignature;
            
            M 1 Reply Last reply
            0
            • M manel.sam

              @J-Hilk

              Imu::Imu() :
              moving(false)
              {

              serialPort = new QSerialPort("COM3",this);
              
              if (serialPort->open( QIODevice::ReadWrite))
              {
              
                  qDebug()<<"SerialPort"<<serialPort<<"Opened successufly";
              }
              else
              {
                  qDebug()<<serialPort->error();
                  QSerialPortInfo::availablePorts();
              }
              
              if (!serialPort->setBaudRate(57600))
                  log_error("imu","failed to set baudrate, error no %d",serialPort->error());
              serialPort->setDataBits(QSerialPort::Data8);
              serialPort->setParity(QSerialPort::NoParity);
              serialPort->setStopBits(QSerialPort::OneStop); // One Stop bit
              serialPort->setFlowControl(QSerialPort::NoFlowControl);
              qDebug()<<"error"<<serialPort->errorString();
              
              QObject::connect(this->serialPort,SIGNAL(readyRead()),this,SLOT(pollSerialPort()));
              QObject::connect(serialPort, &::QSerialPort::errorOccurred,this,&Imu::handleError);
              
              }
              

              Imu::~Imu()
              {
              serialPort->close();
              }

              void Imu::handleError(QSerialPort::SerialPortError error)
              {
              if (error == QSerialPort::ResourceError){
              qDebug()<<"Handle Error"<<error;
              serialPort->close();
              }
              }

              void Imu::pollSerialPort()
              {

              QByteArray hexData;
              hexData.append(serialPort->readAll().toHex());
              
              qDebug() << "Serial received " << hexData;
              QByteArray data = QByteArray::fromHex(hexData);
              
              // data size
              qInfo() << QStringLiteral("data size is : ") << data.size() << " octets";
              
              QDataStream stream(data);
              
              // Read The BigIndian value
              stream.setByteOrder(QDataStream::BigEndian);
              qint16 headerSignature;
              stream >> headerSignature;
              
              M Offline
              M Offline
              mpergand
              wrote on last edited by mpergand
              #15

              @manel-sam said in Serial data received:

              QByteArray hexData;
              hexData.append(serialPort->readAll().toHex());

              hexData is local, so you append nothing !

              hexData.append(serialPort->readAll().toHex());
              qDebug() << "Serial received " << hexData;
              QByteArray data = QByteArray::fromHex(hexData);

              you convert to ascii then back to binary !!??

              You must check the packet is complete (37 bytes) before processing any further.

              M 1 Reply Last reply
              3
              • M manel.sam

                @JonB Sorry, I copied the wrong code

                I used the readAll once, but I still get the 0 Bytes

                JonBJ Offline
                JonBJ Offline
                JonB
                wrote on last edited by JonB
                #16

                @manel-sam said in Serial data received:

                I used the readAll once, but I still get the 0 Bytes

                And where in your code do you now get this?

                Separately you need to follow @mpergand's comments.

                In handleError() you only report anything if QSerialPort::ResourceError, and silently ignore if any other error, for whatever reason. Please don't write code like this, and certainly not while developing/debugging.

                M 1 Reply Last reply
                0
                • M mpergand

                  @manel-sam said in Serial data received:

                  QByteArray hexData;
                  hexData.append(serialPort->readAll().toHex());

                  hexData is local, so you append nothing !

                  hexData.append(serialPort->readAll().toHex());
                  qDebug() << "Serial received " << hexData;
                  QByteArray data = QByteArray::fromHex(hexData);

                  you convert to ascii then back to binary !!??

                  You must check the packet is complete (37 bytes) before processing any further.

                  M Offline
                  M Offline
                  manel.sam
                  wrote on last edited by manel.sam
                  #17

                  @mpergand Yes it was just to visualize the data in hexa as in the documentation of my sensor, then I preferred to work in binary.

                  So the append I should do it where§?

                  M 1 Reply Last reply
                  0
                  • M manel.sam

                    @mpergand Yes it was just to visualize the data in hexa as in the documentation of my sensor, then I preferred to work in binary.

                    So the append I should do it where§?

                    M Offline
                    M Offline
                    mpergand
                    wrote on last edited by mpergand
                    #18

                    @manel-sam said in Serial data received:

                    So the append I should do it where§?

                    Create a member variable in your imu class.

                        // _packetData  member variable of imu
                        _packetData.append(serialPort->readAll());
                        
                        if(_packetData.size()>=PACKET_LENGTH)
                            {
                            // packet complete
                            qInfo() << QStringLiteral("data size is : ") << _packetData.size() << " octets";
                            qDebug() << "Serial received " << _packetData.toHex();
                            
                            // go ahead with this packet
                            QDataStream stream(_packetData);
                            
                            // Read The BigIndian value
                            stream.setByteOrder(QDataStream::BigEndian);
                            qint16 headerSignature;
                            stream >> headerSignature;
                            }
                    

                    You may also check the data received don't exceed PACKET_LENGTH, cause it means you have already received data from the next packet. (it may be irrelevant in your case, I don't kown)

                    1 Reply Last reply
                    0
                    • JonBJ JonB

                      @manel-sam said in Serial data received:

                      I used the readAll once, but I still get the 0 Bytes

                      And where in your code do you now get this?

                      Separately you need to follow @mpergand's comments.

                      In handleError() you only report anything if QSerialPort::ResourceError, and silently ignore if any other error, for whatever reason. Please don't write code like this, and certainly not while developing/debugging.

                      M Offline
                      M Offline
                      manel.sam
                      wrote on last edited by manel.sam
                      #19
                      This post is deleted!
                      1 Reply Last reply
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