QModbusDevice connect/disconnect

[J.Hilk]

Hello everyone,

I'm useing the QModbusDevice class to exchange data over a serial bus with an external device.

So far everything works fine, but the programm needs to be as fool proof as possible, so I need to catch wrong parameters, reconnects, etc.

When I call void QModbusDevice::disconnectDevice(), the state QModbusClient does not change from QModbusDevice::ClosingState to QModbusDevice::UnconnectedState and therefore does not accept new parameters and does not allow a reconnect.

I was able to circumvent this by re-initializating the QModbusClient. But there has to be a better way.

The question:
What is the right way to disconnect a QModbusClient?

Here, the 2 functions I wrote, that handle the Connect/Disconnet:

void Modbus::connectDevice(bool connect)
{
    qDebug() << "connectDevice" << connect << mDevice->state();

    if(connect){
        switch (mDevice->state()) {
        
        case QModbusDevice::ClosingState:
        case QModbusDevice::ConnectedState:
        case QModbusDevice::ConnectingState:
            mDevice->deleteLater();
            mDevice = new QModbusRtuSerialMaster(this);
            setupSignalSlots();
            QTimer::singleShot(100,this, [=]{setConnectParamter(m_port,m_paramter);});
            break;
        
        case QModbusDevice::UnconnectedState:
        default:
            if(!mDevice->connectDevice()){
                emit signalModbusError("Verbindungsfehler: "+mDevice->errorString());
                mDevice->disconnectDevice();
            }
            break;
        }
    }else{
        mDevice->disconnectDevice();
    }
}

void Modbus::setConnectParamter(QString port, QList<int> Paramter)
{
    qDebug() << "setConnectParamter" << port << Paramter;
    if(!mDevice){
        qDebug() << "Error setConnectParamter";
        emit signalModbusError("Modbus not initialised!");
        return;
    }
    if(Paramter.size() >= 7){
        m_paramter = Paramter; m_port = port;
        mDevice->setConnectionParameter(QModbusDevice::SerialPortNameParameter,port);
        mDevice->setConnectionParameter(QModbusDevice::SerialParityParameter, Paramter[0]);
        mDevice->setConnectionParameter(QModbusDevice::SerialBaudRateParameter,Paramter[1]);
        mDevice->setConnectionParameter(QModbusDevice::SerialDataBitsParameter,Paramter[2]);
        mDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,Paramter[3]);
        mDevice->setTimeout(Paramter[4]);
        mDevice->setNumberOfRetries(Paramter[5]);
        deviceID = Paramter[6];
        connectDevice(true);
    }else{
        qDebug() << " Error setConnectParamter, Parameter mismatch";
    }
}

[tangxinzhou]

Excuse , do you have the answer to this question? I encountered the same problem.

[J.Hilk]

@tangxinzhou I'm afraid I do not have a solid solutions. I'm running a workaround now.

Let me post it for you:

void connectDevice(bool connect)
{
    if(connect){
        switch (mDevice->state()) {

        case QModbusDevice::ClosingState:
        case QModbusDevice::ConnectedState:
        case QModbusDevice::ConnectingState:
            mDevice->deleteLater();
            mDevice = new QModbusRtuSerialMaster(this);
            setupSignalSlots();
            QTimer::singleShot(100,this, [=]{setConnectParamter(m_port,m_paramter);});
            break;

        case QModbusDevice::UnconnectedState:
        default:
            if(!mDevice->connectDevice()){
                emit signalModbusError(mDevice->errorString());
                mDevice->disconnectDevice();
            }
            break;
        }
    }else{
        stopPoll();
        mDevice->disconnectDevice();
        QTimer::singleShot(200,this,[=]{checkDisconnected();});
    }
}

void checkDisconnected()
{
    if(mDevice->state() != QModbusDevice::UnconnectedState){
        mDevice->deleteLater();
        mDevice = new QModbusRtuSerialMaster(this);
        setupSignalSlots();
    }
}