Modbus TCP Client write holding registers

Damian7546

Hi,

I wrote simple Modbus TCP client to reading Input Registers cyclicly. It works Now I would like to write value to Holding Register form Modbus TCP Client, so I wrote wr_redy function to my thread, but I do not know how run it, any idea ?

void ClientMachine1::run()
{
    QModbusTcpClient mc;
    QTimer tim_event_timer;
    tim_event_timer.setSingleShot(true);
    QModbusDataUnit du(QModbusDataUnit::InputRegisters,0,10);
    QModbusReply *replyRd;
    QModbusDataUnit wr(QModbusDataUnit::HoldingRegisters,0,10);


    //define modbus write function
    auto wr_redy = [&](){
        for(int i=0; i < 10; i++)
            wr.setValue(i, m_holdRegArray[i]);
        if (auto *replyWr = mc.sendWriteRequest(wr,255)){
            if (!replyWr->isFinished()) {
                connect(replyWr, &QModbusReply::finished, this, [this, replyWr]() {
                    if (replyWr->error() == QModbusDevice::ProtocolError) {
                        qDebug() << "Modbus TCP Client write response error";
                    } else if (replyWr->error() != QModbusDevice::NoError) {
                        qDebug() << "Modbus TCP Client write response error";
                    }
                    replyWr->deleteLater();
                });
            } else {
                replyWr->deleteLater();
            }
        }
        else {
            qDebug() << "Modbus TCP Client write error";
        }
    };

    //define modbus reply function
    auto rpl_redy =[&](){
        if(!replyRd->error()){
            emit updateDataInReg(id, replyRd->result().value(0)
                                 , replyRd->result().value(1)
                                 , replyRd->result().value(2)
                                 , replyRd->result().value(3)
                                 , replyRd->result().value(4)
                                 , replyRd->result().value(5)
                                 , replyRd->result().value(6)
                                 , replyRd->result().value(7)
                                 , replyRd->result().value(8)
                                 , replyRd->result().value(9));
        }else{
            exit();
        }
        replyRd->deleteLater();
    };

    //define timer timeout function
    auto timeoutRd = [&](){
        replyRd=mc.sendReadRequest(du,255);
        if(replyRd->isFinished()){
            delete replyRd;
        }else{
            connect(replyRd,&QModbusReply::finished,rpl_redy);
        }
    };

    //define modbus device state change function
    auto stateChange = [&](QModbusClient::State state){
        if(state==QModbusClient::ConnectedState){
            tim_event_timer.start(1000);
            qDebug() << "ModbusTCPClient is connected";
        }else if(state==QModbusClient::UnconnectedState){
            qDebug() << "ModbusTCPClient is disconnected";
            exit();
        }
    };



    connect(&tim_event_timer, &QTimer::timeout,timeoutRd);
    connect(&mc, &QModbusClient::stateChanged,stateChange);



    mc.setConnectionParameter(QModbusDevice::NetworkAddressParameter, "192.168.1.18");
    mc.setConnectionParameter(QModbusDevice::NetworkPortParameter, 5020);
    mc.setTimeout(500);
    if(!mc.connectDevice()){
        exit();
        return;
    }
    exec();
}

jsulm

@Damian7546 If you want to connect a lambda to a signal then do it properly:

connect(this, ClientMachine1::holdRegArrayChanged, this, wr_redy);

wr_redy is NOT a member of your class, so simply do not prefix it with your class name.

Damian7546

How connect wr_redy to signal from ClientMachine1 , inside run() ?

jsulm

@Damian7546 said in Modbus TCP Client write holding registers:

How connect wr_redy to signal from ClientMachine1 , inside run() ?

Using connect.
What exact problem do you have?

Damian7546

Look..
I wold like call wr_ready when QbyteArray (m_holdRegArray) was changed, so I created code like below:


void ClientMachine1::run()
{
   ///my Modbus TCP Client code 
   ///........  
   how connect wr_redy  with  signal   holdRegArrayChanged 	
   
}

QByteArray ClientMachine1::holdRegArray() const
{
    return m_holdRegArray;
}

void ClientMachine1::setHoldRegArray(const QByteArray &newHoldRegArray)
{
    if (m_holdRegArray == newHoldRegArray)
        return;
    m_holdRegArray = newHoldRegArray;
    emit holdRegArrayChanged();
}

How connect holdRegArrayChanged with wr_ready inside run() thread ?

jsulm

@Damian7546 I still don't understand the problem. If wr_ready is a slot and holdRegArrayChanged a signal then simply connect them like any other signal/slot. Can you explain what exactly is not clear?

Damian7546

Because wr_ready is not visible in the constructor:

ClientMachine1::ClientMachine1(QObject *parent)
    : QThread{parent}
{

    connect(this, ClientMachine1::holdRegArrayChanged, this, ClientMachine1::wr_ready);
}

In othe hand, the holdRegArrayChanged I can not connect inside run() because I have errors:

Reference to non-static member function must be called; did you mean to call it with no arguments? (fix available)
insert '()'

No member named 'wr_redy' in 'ClientMachine1'

jsulm

@Damian7546 said in Modbus TCP Client write holding registers:

Because wr_ready is not visible in the constructor

Of course it's not, because you defined it inside run().
Simply define it as normal member of ClientMachine1...

Damian7546

Can you tell me how create definition in *.h file to my wr_redy lambda contruction and auto type ?

jsulm

@Damian7546 said in Modbus TCP Client write holding registers:

Can you tell me how create definition in *.h file to my wr_redy lambda contruction and auto type ?

Why does it have to be a lambda?

jsulm

@Damian7546 I'm also wondering why you use threads at all?
If you need to do something periodically then simply use QTimer.

Damian7546

@jsulm said in Modbus TCP Client write holding registers:

@Damian7546 said in Modbus TCP Client write holding registers:

Can you tell me how create definition in *.h file to my wr_redy lambda contruction and auto type ?

Why does it have to be a lambda?

I just want to know how to do it - for my own knowledge

Damian7546

@jsulm said in Modbus TCP Client write holding registers:

@Damian7546 I'm also wondering why you use threads at all?
If you need to do something periodically then simply use QTimer.

I would like to run Client on thread and test with several clients(threads) ... how will it be with stability and read/write speed,
So how define wr_redy in *.h file ?

jsulm

@Damian7546 said in Modbus TCP Client write holding registers:

So how define wr_redy in *.h file ?

Don't define it as lambda, but a normal method.

Damian7546

@jsulm How do I do that?
When I declare my function in *.h file :
void wr_redy();

And I will create definition this function outside my run() function , I do not have acces to variables defined in run()...

jsulm

@Damian7546 If you want to connect a lambda to a signal then do it properly:

connect(this, ClientMachine1::holdRegArrayChanged, this, wr_redy);

wr_redy is NOT a member of your class, so simply do not prefix it with your class name.

Damian7546

@jsulm said in Modbus TCP Client write holding registers:

@Damian7546 If you want to connect a lambda to a signal then do it properly:
connect(this, ClientMachine1::holdRegArrayChanged, this, wr_redy);
wr_redy is NOT a member of your class, so simply do not prefix it with your class name.

Right

Damian7546

@jsulm Unfortunetly my write function still doesn't work:/

auto wr_redy = [&](){
            for(int i=0; i < m_holdRegArray.count(); i++){
                qDebug() << "count: " << i;
                wr.setValue(i, m_holdRegArray[i]);
            }
    };

The application was crash when it wr.setValue(i, m_holdRegArray[i]); is called...

jsulm

@Damian7546 said in Modbus TCP Client write holding registers:

The application was crash when

So, did you use debugger to see why it crashes?
What is wr?

Damian7546

@jsulm When I have status: "ModbusTCPClient is disconnected" my app crash when I try write registers..

jsulm

@Damian7546 Then don't write registers if there is no connection...