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Serial communication

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  • D Damian7546

    @Christian-Ehrlicher @JonB Thank you for yours suggestions.

    I have implemented your comments,suggestions, and now code look like:

    #include "mydevice.h"
    
    
    MyDevice::MyDevice(QObject *parent)
        : QObject{parent}
    {
        serial = new QSerialPort();
        serial->setPortName("COM9");
        serial->setBaudRate(QSerialPort::Baud9600);
        serial->setDataBits(QSerialPort::Data8);
        serial->setParity(QSerialPort::EvenParity);
        serial->open(QIODevice::ReadWrite);
    
        connect(serial, &QSerialPort::readyRead, this, &MyDevice::serialRecive);
    
        connect(&timerResponse, &QTimer::timeout, this, [&](){  m_timeoutResponse = true;
                                                                timerResponse.stop();
                                                                qDebug()<<"Timeout response";}
    
        );
        connect(&timerState, &QTimer::timeout, this, &MyDevice::stateMachine);
    
    
    
        if(!serial->isOpen()){
            qInfo() << "Serial port status: " << serial->isOpen();
        }else{
            //run state machine!
            m_state = State::state::STATUS_REQUEST;
            timerState.start(100);
        }
    
    
    
    }
    
    void MyDevice::serialRecive()
    {
        m_request_part.append(serial->readAll());
        qDebug() << "Partially received: " << m_request_part;
    
        while(!messageComplete(m_request_part)) {
            return;
        }
    
        bool crcValid=validateResponse(m_request_part);
        if(!crcValid){
            qDebug()<<"Crc error";
            m_state = State::state::STATUS_REQUEST;
            return;
        }
    
        timerResponse.stop();
        m_request = m_request_part;
        qDebug()<<"Correct response: " << m_request;
    }
    
    
    
    void MyDevice::stateMachine()
    {
        if (m_request.count() > 3)
            m_responseStatus = static_cast<Response::Status>(m_request.mid(2,1).toInt(nullptr, 16));
        else
            m_responseStatus = Response::Status::UNKNOWN;
    
    
        switch (m_state)
        {
        case State::state::STATUS_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::POLL,m_data));
            m_state = State::state::STATUS_RESPONSE;
            break;
        case State::state::STATUS_RESPONSE:
            if(m_responseStatus == Response::Status::POWER_UP)  m_state = State::state::VERSION_REQUEST;
            if(m_responseStatus == Response::Status::POWER_UP_WITH_BILL_IN_ACCEPTOR) m_state = State::state::RESET_REQUEST;
            if(m_responseStatus == Response::Status::POWER_UP_WITH_BILL_IN_STACKER) m_state = State::state::RESET_REQUEST;
            if(m_responseStatus == Response::Status::INITIALIZE) m_state = State::state::EN_DIS_REQUEST;
            if(m_responseStatus == Response::Status::ENABLE) m_state = State::state::STATUS_REQUEST;
            if(m_responseStatus == Response::Status::ACCEPTING) m_state = State::state::STATUS_REQUEST;
            if(m_responseStatus == Response::Status::ESCROW) m_state = State::state::STACK1_REQUEST;
            if(m_responseStatus == Response::Status::STACKING) m_state = State::state::STATUS_REQUEST;
            if(m_responseStatus == Response::Status::STACKED) m_state = State::state::STATUS_REQUEST;
            if(m_responseStatus == Response::Status::VALID) m_state = State::state::ACK_REQUEST;
            if(m_responseStatus == Response::Status::REJECTING) m_state = State::state::STATUS_REQUEST;
            if(m_responseStatus == Response::Status::JAM_IN_ACCEPTOR) m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
        case State::state::VERSION_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::GET_VERSION,m_data));
            m_state = State::state::VERSION_RESPONSE;
            break;
        case State::state::VERSION_RESPONSE:
            if(m_responseStatus == Response::Status::STAT_VERSION) m_state = State::state::RESET_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
        case State::state::RESET_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::RESET,m_data));
            m_state = State::state::RESET_RESPONSE;
            break;
        case State::state::RESET_RESPONSE:
            if(m_responseStatus == Response::Status::ACK) m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
        case State::state::EN_DIS_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            m_data = QByteArray("\xff\xff",2);
            serial->write(createMessage(Commands::deviceCommand::ENABLE,m_data));
            m_state = State::state::EN_DIS_RESPONSE;
            break;
        case State::state::EN_DIS_RESPONSE:
            if(m_responseStatus == Response::Status::STAT_EN_DIS) m_state = State::state::SECURITY_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
        case State::state::SECURITY_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            m_data = QByteArray("\xff\xff",2);
            serial->write(createMessage(Commands::deviceCommand::SECURITY,m_data));
            m_state = State::state::SECURITY_REQUEST;
            break;
        case State::state::SECURITY_RESPONSE:
            if(m_responseStatus == Response::Status::CMD_ENABLE_SECURITY) m_state = State::state::OPTIONAL_FUN_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
    
        case State::state::OPTIONAL_FUN_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::OPTIONAL,m_data));
            m_state = State::state::OPTIONAL_FUN_RESPONSE;
            break;
        case State::state::OPTIONAL_FUN_RESPONSE:
            if(m_responseStatus == Response::Status::CMD_OPTIONAL) m_state = State::state::INHIBIT_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
        case State::state::INHIBIT_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::INHIBIT,m_data));
            m_state = State::state::INHIBIT_RESPONSE;
            break;
        case State::state::INHIBIT_RESPONSE:
            if(m_responseStatus == Response::Status::CMD_INHIBIT)  m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
        case State::state::STACK1_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::STACK1,m_data));
            m_state = State::state::STACK1_RESPONSE;
            break;
    
        case State::state::STACK1_RESPONSE:
            if(m_responseStatus == Response::Status::ACK) m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
    
        case State::state::STACK2_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::STACK2,m_data));
            m_state = State::state::STACK2_RESPONSE;
            break;
    
        case State::state::STACK2_RESPONSE:
            if(m_responseStatus == Response::Status::ACK) m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
    
    
    
    
    
        case State::state::ACK_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::ACK,m_data));
            m_state = State::state::STATUS_REQUEST;
            break;
    
    
    
    
    
    
        case State::state::RETURN_REQUEST:
            timerResponse.start(m_timeout);
            clearBuffers();
            serial->write(createMessage(Commands::deviceCommand::RETURN,m_data));
            m_state = State::state::RETURN_RESPONSE;
            break;
    
        case State::state::RETURN_RESPONSE:
            if(m_responseStatus == Response::Status::ACK) m_state = State::state::STATUS_REQUEST;
            if(m_timeoutResponse) {
                m_timeoutResponse = false;
                m_state = State::state::STATUS_REQUEST;
            }
            break;
        default:
            break;
        }
    
    
    }
    
    void MyDevice::clearBuffers()
    {
        m_request.clear();
        m_data.clear();
        m_request_part.clear();
    }
    
    bool MyDevice::messageComplete(const QByteArray &data) const
    {
        if(data.size()>=3){
            quint8 length=(unsigned char)data[1];
            if(length==data.length())
                return true;
        }
        return false;
    }
    
    bool MyDevice::validateResponse(QByteArray data)
    {
        if(data.size()<3)
            return false;
    
        QByteArray crc=data.right(2);
        std::reverse(crc.begin(),crc.end());
        bool ok=false;
    
        quint16 messageCRC=crc.toHex().toUInt(&ok,16);
        if(!ok)
            return false;
    
        data.chop(2);
    
        return (messageCRC==crc16(data));
    }
    QByteArray MyDevice::createMessage(const Commands::deviceCommand &cmd, const QByteArray &data)
    {
        QByteArray message;
        message.append(0xFC);
    
        if(data.count() > 0) {
            message.append(0x05+data.count());
        }
        else{
            message.append(0x05);
        }
        message.append((char)cmd);
    
        if(data.count() > 0) {
            for (int i= 0 ; i< data.count() ; i++)
                message.append(data[i]);
        }
    
    
        quint16 crc=crc16(message);
        QByteArray crcData=QByteArray((char *)&crc,2);
    
        message.append(crcData);
    
        return message;
    
    
    }
    
    quint16 MyDevice::crc16(const QByteArray &data)
    {
        unsigned int CRC;
        unsigned char j;
        CRC = 0;
        for(int i=0; i < data.size(); i++)
        {
            CRC ^= (unsigned char)data[i];
            for(j=0; j < 8; j++)
            {
                if(CRC & 0x0001) {CRC >>= 1; CRC ^= POLYNOMIAL;}
                else CRC >>= 1;
            }
        }
        return CRC;
    }
    
    
    

    I would be rally gratefull for more suggestions.

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by jsulm
    #14

    @Damian7546 said in Serial communication:

    while(!messageComplete(m_request_part)) {
    return;
    }

    Why do you have a loop here if you anyway do a return?

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    D 1 Reply Last reply
    1
    • jsulmJ jsulm

      @Damian7546 said in Serial communication:

      while(!messageComplete(m_request_part)) {
      return;
      }

      Why do you have a loop here if you anyway do a return?

      D Offline
      D Offline
      Damian7546
      wrote on last edited by
      #15

      @jsulm Better?

      if(!messageComplete(m_request_part)) {
      return;
      }
      
      JonBJ 1 Reply Last reply
      1
      • D Damian7546

        @jsulm Better?

        if(!messageComplete(m_request_part)) {
        return;
        }
        
        JonBJ Offline
        JonBJ Offline
        JonB
        wrote on last edited by
        #16

        @Damian7546 More readable/clear :)

        Christian EhrlicherC 1 Reply Last reply
        0
        • JonBJ JonB

          @Damian7546 More readable/clear :)

          Christian EhrlicherC Offline
          Christian EhrlicherC Offline
          Christian Ehrlicher
          Lifetime Qt Champion
          wrote on last edited by
          #17

          From my pov the parsing is incorrect as there may be more than one message in the buffer so the second (or even the first part of the second) is thrown away.

          Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
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          D 1 Reply Last reply
          1
          • Christian EhrlicherC Christian Ehrlicher

            From my pov the parsing is incorrect as there may be more than one message in the buffer so the second (or even the first part of the second) is thrown away.

            D Offline
            D Offline
            Damian7546
            wrote on last edited by
            #18

            @Christian-Ehrlicher so how to fix it?

            JonBJ 1 Reply Last reply
            0
            • D Damian7546

              @Christian-Ehrlicher so how to fix it?

              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by
              #19

              @Damian7546
              Remove only what is used for a message from the buffer, leaving any further unused bytes there might be for appending to create next "message".

              1 Reply Last reply
              0
              • jsulmJ jsulm

                @Damian7546 Something like this. But better don't use c-style casts:

                m_responseStatus = static_cast<Response::Status>(m_request.mid(2,1).toInt(nullptr, 16));
                
                D Offline
                D Offline
                Damian7546
                wrote on last edited by Damian7546
                #20

                @jsulm
                This conversion doesn't work.

                class Response
                {
                public:
                    enum class Status : quint8{
                         DISABLE = 0x1A,
                    };
                    Response();
                };
                
                

                In m_responseStatus variable I have 0x1A value, but below statement is not equal:

                m_responseStatus = static_cast<Response::Status>(m_request.mid(2,1).toInt(nullptr, 16));
                    qDebug() << "m_responseStatus: " << m_request.mid(2,1);
                
                    if(Response::Status::DISABLE == m_responseStatus)
                        qDebug() << "ok convert";
                    else
                        qDebug() << "bad convert";
                
                

                Problem is in toInt conversion:

                qDebug() << "m_responseStatus: " << m_request.mid(2,1);
                qDebug() << "m_responseStatus: " << m_request.mid(2,1).toInt(nullptr, 16);
                

                result:
                m_responseStatus: "\x1A"
                m_responseStatus: 0

                JonBJ 1 Reply Last reply
                0
                • D Damian7546

                  @jsulm
                  This conversion doesn't work.

                  class Response
                  {
                  public:
                      enum class Status : quint8{
                           DISABLE = 0x1A,
                      };
                      Response();
                  };
                  
                  

                  In m_responseStatus variable I have 0x1A value, but below statement is not equal:

                  m_responseStatus = static_cast<Response::Status>(m_request.mid(2,1).toInt(nullptr, 16));
                      qDebug() << "m_responseStatus: " << m_request.mid(2,1);
                  
                      if(Response::Status::DISABLE == m_responseStatus)
                          qDebug() << "ok convert";
                      else
                          qDebug() << "bad convert";
                  
                  

                  Problem is in toInt conversion:

                  qDebug() << "m_responseStatus: " << m_request.mid(2,1);
                  qDebug() << "m_responseStatus: " << m_request.mid(2,1).toInt(nullptr, 16);
                  

                  result:
                  m_responseStatus: "\x1A"
                  m_responseStatus: 0

                  JonBJ Offline
                  JonBJ Offline
                  JonB
                  wrote on last edited by JonB
                  #21

                  @Damian7546 said in Serial communication:

                  In m_responseStatus variable I have 0x1A value, but below statement is not equal:

                  Sorry, I don't believe that. Start with:

                  qDebug() << int(m_responseStatus)  << int(Response::Status::DISABLE) << 0x1A;
                  

                  [I assume int() is good enough here to test. You can go static_cast<int>(...) if necessary.]

                  D 1 Reply Last reply
                  0
                  • JonBJ JonB

                    @Damian7546 said in Serial communication:

                    In m_responseStatus variable I have 0x1A value, but below statement is not equal:

                    Sorry, I don't believe that. Start with:

                    qDebug() << int(m_responseStatus)  << int(Response::Status::DISABLE) << 0x1A;
                    

                    [I assume int() is good enough here to test. You can go static_cast<int>(...) if necessary.]

                    D Offline
                    D Offline
                    Damian7546
                    wrote on last edited by
                    #22

                    @JonB said in Serial communication:

                    Sorry, I don't believe that. Start with:
                    qDebug() << int(m_responseStatus) << int(Response::Status::DISABLE) << 0x1A;

                    Result:
                    0 26 26

                    JonBJ 1 Reply Last reply
                    0
                    • D Damian7546

                      @JonB said in Serial communication:

                      Sorry, I don't believe that. Start with:
                      qDebug() << int(m_responseStatus) << int(Response::Status::DISABLE) << 0x1A;

                      Result:
                      0 26 26

                      JonBJ Offline
                      JonBJ Offline
                      JonB
                      wrote on last edited by JonB
                      #23

                      @Damian7546
                      So you have your answer from the first 2 outputs. 0 != 26, the two values being compared are indeed not equal/the same.

                      Behaviour is quite correct given your m_request.mid(2,1).toInt(nullptr, 16);, which (QByteArray::toInt()) is quite incorrect to use on your byte array containing a byte with value \x16 (26). toInt() is not for use in your case, as you do not have a string representation of an integer to convert.

                      D 1 Reply Last reply
                      0
                      • JonBJ JonB

                        @Damian7546
                        So you have your answer from the first 2 outputs. 0 != 26, the two values being compared are indeed not equal/the same.

                        Behaviour is quite correct given your m_request.mid(2,1).toInt(nullptr, 16);, which (QByteArray::toInt()) is quite incorrect to use on your byte array containing a byte with value \x16 (26). toInt() is not for use in your case, as you do not have a string representation of an integer to convert.

                        D Offline
                        D Offline
                        Damian7546
                        wrote on last edited by
                        #24

                        @JonB So ho to compare Response::Status::DISABLE to byte in QByteArray m_request[2] ?

                        JonBJ 1 Reply Last reply
                        0
                        • D Damian7546

                          @JonB So ho to compare Response::Status::DISABLE to byte in QByteArray m_request[2] ?

                          JonBJ Offline
                          JonBJ Offline
                          JonB
                          wrote on last edited by
                          #25

                          @Damian7546
                          Exactly as you have just written it!

                          qDebug() << Response::Status::DISABLE << m_request[2];
                          

                          [You may have to do casting.] Sightly better is to use m_request.at(2) in place of m_request[2] here, but that is a detail and not related to your issue. You want to inspect the actual bytes in the QByteArray, not call QByteArray::toInt().

                          J.HilkJ 1 Reply Last reply
                          1
                          • JonBJ JonB

                            @Damian7546
                            Exactly as you have just written it!

                            qDebug() << Response::Status::DISABLE << m_request[2];
                            

                            [You may have to do casting.] Sightly better is to use m_request.at(2) in place of m_request[2] here, but that is a detail and not related to your issue. You want to inspect the actual bytes in the QByteArray, not call QByteArray::toInt().

                            J.HilkJ Offline
                            J.HilkJ Offline
                            J.Hilk
                            Moderators
                            wrote on last edited by
                            #26

                            @JonB casting is highly suggested, as Response::Status is an uint_8t and at() returns a char, aka int8_t


                            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.

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

                              @JonB casting is highly suggested, as Response::Status is an uint_8t and at() returns a char, aka int8_t

                              JonBJ Offline
                              JonBJ Offline
                              JonB
                              wrote on last edited by JonB
                              #27

                              @J-Hilk
                              Yes, but what I meant is I don't have anything available to test what compiler says as I write answers. So that detail is left to OP :) Since the OP asks about comparing (with ==) one should be able to compare a unit_8t against a char/int8_t, I think, using C++ automatic expression promotion without bothering to cast/convert, I think? But maybe not/warning for enum value against integer?

                              The important thing is no QByteArray::toInt() here!

                              D J.HilkJ 2 Replies Last reply
                              0
                              • JonBJ JonB

                                @J-Hilk
                                Yes, but what I meant is I don't have anything available to test what compiler says as I write answers. So that detail is left to OP :) Since the OP asks about comparing (with ==) one should be able to compare a unit_8t against a char/int8_t, I think, using C++ automatic expression promotion without bothering to cast/convert, I think? But maybe not/warning for enum value against integer?

                                The important thing is no QByteArray::toInt() here!

                                D Offline
                                D Offline
                                Damian7546
                                wrote on last edited by Damian7546
                                #28

                                @JonB It doesn't work:
                                qDebug() << static_cast<int>(Response::Status::DISABLE) << m_request.at(2);

                                Result:
                                ASSERT: "uint(i) < uint(size())" in file C:/Qt/5.15.2/mingw81_32/include/QtCore/qbytearray.h, line 500

                                And this way:
                                qDebug() << static_cast<int>(Response::Status::DISABLE) << m_request[2];

                                Result:
                                Bez tytułu.jpg

                                Where :
                                m_request response: "\xFC\x05\x1A\xF4\xE8"

                                JonBJ 1 Reply Last reply
                                0
                                • D Damian7546

                                  @JonB It doesn't work:
                                  qDebug() << static_cast<int>(Response::Status::DISABLE) << m_request.at(2);

                                  Result:
                                  ASSERT: "uint(i) < uint(size())" in file C:/Qt/5.15.2/mingw81_32/include/QtCore/qbytearray.h, line 500

                                  And this way:
                                  qDebug() << static_cast<int>(Response::Status::DISABLE) << m_request[2];

                                  Result:
                                  Bez tytułu.jpg

                                  Where :
                                  m_request response: "\xFC\x05\x1A\xF4\xE8"

                                  JonBJ Offline
                                  JonBJ Offline
                                  JonB
                                  wrote on last edited by JonB
                                  #29

                                  @Damian7546
                                  How difficult to try:

                                  qDebug() << static_cast<int>(Response::Status::DISABLE) << static_cast<int>(m_request[2]);
                                  // or
                                  qDebug() << static_cast<int>(Response::Status::DISABLE) << static_cast<int>(m_request.at(2));
                                  

                                  ? I leave you to resolve the C++ to your satisfaction.

                                  D 1 Reply Last reply
                                  0
                                  • JonBJ JonB

                                    @J-Hilk
                                    Yes, but what I meant is I don't have anything available to test what compiler says as I write answers. So that detail is left to OP :) Since the OP asks about comparing (with ==) one should be able to compare a unit_8t against a char/int8_t, I think, using C++ automatic expression promotion without bothering to cast/convert, I think? But maybe not/warning for enum value against integer?

                                    The important thing is no QByteArray::toInt() here!

                                    J.HilkJ Offline
                                    J.HilkJ Offline
                                    J.Hilk
                                    Moderators
                                    wrote on last edited by
                                    #30

                                    @JonB said in Serial communication:

                                    one should be able to compare a unit_8t against a char/int8_t, I think, using C++ automatic expression promotion without bothering to cast/convert, I think?

                                    nono, comparing different types via == or != will never promote any side "automatically"

                                    you can get something like that fi you wrap it in a function call or something but.

                                    But comparing uint8_t and int_8 will only work correctly if both values are between 0 and 128.


                                    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.

                                    JonBJ 1 Reply Last reply
                                    0
                                    • JonBJ JonB

                                      @Damian7546
                                      How difficult to try:

                                      qDebug() << static_cast<int>(Response::Status::DISABLE) << static_cast<int>(m_request[2]);
                                      // or
                                      qDebug() << static_cast<int>(Response::Status::DISABLE) << static_cast<int>(m_request.at(2));
                                      

                                      ? I leave you to resolve the C++ to your satisfaction.

                                      D Offline
                                      D Offline
                                      Damian7546
                                      wrote on last edited by
                                      #31

                                      @JonB Sill of topic.
                                      I have variable: Response::Status m_responseStatus.
                                      How properly assign byte form QByteArray to m_responseStatus?

                                      J.HilkJ 1 Reply Last reply
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                                      • D Damian7546

                                        @JonB Sill of topic.
                                        I have variable: Response::Status m_responseStatus.
                                        How properly assign byte form QByteArray to m_responseStatus?

                                        J.HilkJ Offline
                                        J.HilkJ Offline
                                        J.Hilk
                                        Moderators
                                        wrote on last edited by
                                        #32

                                        @Damian7546 you were originally pretty spot on:

                                        static_cast<Response::Status>(m_request.at(0));
                                        

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


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

                                        JonBJ D 2 Replies Last reply
                                        0
                                        • J.HilkJ J.Hilk

                                          @JonB said in Serial communication:

                                          one should be able to compare a unit_8t against a char/int8_t, I think, using C++ automatic expression promotion without bothering to cast/convert, I think?

                                          nono, comparing different types via == or != will never promote any side "automatically"

                                          you can get something like that fi you wrap it in a function call or something but.

                                          But comparing uint8_t and int_8 will only work correctly if both values are between 0 and 128.

                                          JonBJ Offline
                                          JonBJ Offline
                                          JonB
                                          wrote on last edited by JonB
                                          #33

                                          @J-Hilk said in Serial communication:

                                          nono, comparing different types via == or != will never promote any side "automatically"

                                          Umm, C or C++

                                              char c('A');
                                              if (c == 65)
                                              {}
                                          
                                          example.cpp
                                          Compiler returned: 0
                                          

                                          From Godbolt. That's "automatically promoting" char c to int 65, per C/C++ expression rules. Has done since K&R... ?
                                          https://en.cppreference.com/w/cpp/language/implicit_conversion, e.g. Integral conversions topic.

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