QModbusRtuSerialMaster wrong CRC received

juanras

Hello, I'm trying to deploy an QT application to communicate with a slave device on MODBUS RTU RS-485, on an embedded linux board.
I have correctly set up my development environment with QT Creator 5.1 and their corresponding Compiler, debugger obtained from the Yocto SDK.

When I try to run my application to read some registers or when i sendReadRequest I'm always getting a wrong CRC received.

void modbusMaster::readRegisterData(quint16 startAddress, quint16 num, quint16 slaveAddress)
{
if(!m_master)
return;

qDebug()<<"Read Register Data";


QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters,startAddress,num);

if(auto *reply = m_master->sendReadRequest(readUnit,slaveAddress))
{

    qDebug() << reply->isFinished();

    if(!reply->isFinished())
    {
        connect(reply,&QModbusReply::finished,this,&modbusMaster::readyRead);
    }
    else
    {
        delete reply;
    }

}
else
{
    qDebug()<<m_master->errorString();
}

}

void modbusMaster::readyRead()
{
qDebug()<<"Ready Read Function";

auto reply = qobject_cast<QModbusReply*>(sender());
if(!reply)
    return;


if(reply->error() == QModbusDevice::NoError)
{
    //qDebug() << "Reply";
    const QModbusDataUnit unit = reply->result();

    for(uint i=0; i< unit.valueCount();i++)
    {
       const QString entry = tr("Address: %1, Value: %2").arg(unit.startAddress() + i)
                                     .arg(QString::number(unit.value(i),
                                          unit.registerType() <= QModbusDataUnit::Coils ? 10 : 16));

       qDebug()<<entry;

       //emit readData_signal(unit.startAddress()+i,unit.value(i));

    }

}
else if (reply->error() == QModbusDevice::ProtocolError) {
    qDebug()<<"error Protocol Error"<<reply->errorString();
}
else {
    qDebug()<<"error:"<<reply->errorString();
}

reply->deleteLater();

}

The response I get is:

Init mosbusMaster Class
Read Register Data
false
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 0 , calculated CRC: 8432
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 2020 , calculated CRC: 9022
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 0 , calculated CRC: 8432
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 2020 , calculated CRC: 9022
Ready Read Function
error: "Request timeout."

I have tried to debug my application in many ways but I cannot stil make it work.

Does anyone have some related issues with the ModbusRtuSerialMasterClass?

Thanks