Serial communication

[Damian7546]

Hi,

I would like to write serial communication to my device but I don't know how start. I would be really grateful if anyone can get me code skeleton to realising below timing diagram:

I was thinking about using an example: "Blocking Master Example", and use three signals:

void response(const QString &s);
void error(const QString &s);
void timeout(const QString &s);

And inside the response slot I should use state machine based about switch instruction ?

Please for any tips.

[J.Hilk]

@Damian7546 yes, but not the cast or assignment fails, but the access of your QByteArray, it doesn't have 3 Bytes in it and you try to access it outside of the range

[J.Hilk]

@Damian7546 said in Serial communication:

I was thinking about using an example: "Blocking Master Example"

No, please use the async and not the blocking functions. The blocking ones are only meant to be used on systems without an event loop.

You can either do your "State machine" yourself, or you use the convenient https://doc.qt.io/qt-6/qstatemachine.html class :D

---

+1 for ai generated code examples:

#include <QCoreApplication>
#include <QStateMachine>
#include <QSerialPort>
#include <QTimer>
#include <QDebug>

class SerialComm : public QObject
{
    Q_OBJECT
    QStateMachine machine;
    QState *s1;
    QState *s2;
    QSerialPort serial;
    QTimer timer;

public:
    SerialComm() {
        s1 = new QState();
        s2 = new QState();

        s1->addTransition(this, SIGNAL(requestSent()), s2);
        s2->addTransition(this, SIGNAL(doneReading()), s1);
        s2->addTransition(&timer, SIGNAL(timeout()), s1);

        machine.addState(s1);
        machine.addState(s2);

        machine.setInitialState(s1);
        machine.start();

        connect(&serial, SIGNAL(readyRead()), this, SLOT(readData()));
        connect(this, SIGNAL(doneReading()), &serial, SLOT(clear()));

        serial.setPortName("COM1");
        serial.setBaudRate(QSerialPort::Baud9600);
        serial.open(QIODevice::ReadWrite);

        timer.setInterval(3000); // 3 seconds timeout
        timer.setSingleShot(true);
    }

public slots:
    void sendRequest() {
        QByteArray request = "Your request data";
        serial.write(request);
        emit requestSent();
        timer.start();
    }

    void readData() {
        QByteArray data = serial.readAll();
        qDebug() << "Received: " << data;
        emit doneReading();
        timer.stop();
    }

signals:
    void doneReading();
    void requestSent();
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    SerialComm comm;
    QTimer::singleShot(0, &comm, SLOT(sendRequest()));
    return a.exec();
}

[Damian7546]

@J-Hilk Would you put in my timing chart to your code? only by using mnemonic

[JonB]

@J-Hilk said in Serial communication:

+1 for ai generated code examples:

Just a shame that it uses SIGNAL()/SLOT() when a far better replacement was introduced before ChatGPT was even born. I guess now these will never, ever be removed from example code if ChatGPT recommends it now....

[Pl45m4]

@JonB

Haha, you are on a misson to personally ban the old syntax from the Internet, aren't you? 🤣

But serious, it's kinda interesting that even beginners who start with Qt6, use the good old Qt4 string based connections :D

[Damian7546]

Back to the topic of discussion, I have a little problem:
I defined class like below:

class Response
{
public:
    enum class Status : quint8{
        ENABLE = 0x11,
    };
    Response();
};

In other class I have defined vriables:

Response::Status m_responseStatus;
QByteArray m_data;

How I can assign below variables ?

m_responseStatus = m_data[2];
if (m_responseStatus == Response::Status::ENABLE)

[jsulm]

@Damian7546 said in Serial communication:

How I can assign below variables ?

You need to extract the part of the byte array containing the status and cast it to Response::Status. You can for example use https://doc.qt.io/qt-6/qbytearray.html#mid to get the part of the byte array containing status, convert it to int using https://doc.qt.io/qt-6/qbytearray.html#toInt and then cast.

[Damian7546]

@jsulm Do you mean about this notation:
m_responseStatus = (Response::Status)m_request.mid(2,1).toInt(nullptr, 16);

?

[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));

[Damian7546]

@jsulm Thank you.

On base above proposition, I prepared conception synchronous serial communication (without blocking) with my device using state machine.

• Firstly I changed old Qt4 string based connections,
• Secondly I prefer use switch instruction instead QStateMachine

This is only skeleton, without any tests . I would like to know yours opinion, What do you think about below solution:

#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.append(serial->readAll());

    while(!messageComplete(m_request) && !m_timeoutResponse) {
        if(!serial->waitForReadyRead(20)){
            qDebug()<<"Incomplete response";
            m_state = State::state::STATUS_REQUEST;
            return;
        }
        m_request.append(serial->readAll());
    }

    bool crcValid=validateResponse(m_request);
    if(!crcValid){
        qDebug()<<"Crc error";
        m_state = State::state::STATUS_REQUEST;
        return;
    }

    if(m_timeoutResponse)
    {
        qDebug()<<"Timeout response";
        m_state = State::state::STATUS_REQUEST;
        return;
    }

    timerResponse.stop();
    qDebug()<<"Correct response: " << m_request;
}



void MyDevice::stateMachine()
{

    m_responseStatus = static_cast<Response::Status>(m_request.mid(2,1).toInt(nullptr, 16));


    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();
}

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;
}

[JonB]

@Damian7546
I have an observation. Perhaps it is me/only a matter of approach or preference, but why do you choose to introduce waitForReadyRead() calls (in a loop) inside the slot handler for readyRead signal? It may work, but mixes asynchronous and synchronous approach.

I would make serialRecive() do nothing if messageComplete(m_request) is false. Just buffer the bytes into m_request and exit the slot (set m_state if appropriate). Then next time readyRead emitted and slot called append the new bytes and see whether now message completed again. When so, process the bytes received in the buffer, either directly in serialRecive(), or probably better emit a messageCompleted() signal of your own from there, and do your processing in a slot on that. Seems cleaner to me, but maybe up to you.

[Christian Ehrlicher]

@JonB said in Serial communication:

It may work, but mixes asynchronous and synchronous approach.

But is also may eat kitten...
Don't do that. Buffer the data read in a member variable and wait for the next readyRead()

[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.

[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?

[Damian7546]

@jsulm Better?

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

[JonB]

@Damian7546 More readable/clear :)

[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.

[Damian7546]

@Christian-Ehrlicher so how to fix it?

[JonB]

@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".

[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