modbus component. a lot of crc errors.

Pavel Romankov

Hello.
I use QModbusRtuSerialMaster class in my project.

if (auto *reply
    = m_modbusDevice->sendReadRequest(QModbusDataUnit(QModbusDataUnit::Coils, 0x0004, 1), 1)) {
    if (!reply->isFinished()) {
        connect(reply, &QModbusReply::finished, this, [this, reply] {
            if (reply->error() == QModbusDevice::NoError) {
               //logic
            } else {
                qDebug() << reply->error();
            }
            reply->deleteLater();
        });
    } else {
        delete reply;
    }
}

And i have a lot of modbus errors like:

qt.modbus: (RTU client) Discarding response with wrong CRC, received: 48379 , calculated CRC: 58176
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 63487 , calculated CRC: 26643
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 40447 , calculated CRC: 9460
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 60062 , calculated CRC: 49258
qt.modbus: (RTU client) Discarding response with wrong CRC, received: 65511 , calculated CRC: 58230

qt.modbus: (RTU client) Cannot match response with open request, ignoring
qt.modbus: (RTU client) Cannot match response with open request, ignoring
qt.modbus: (RTU client) Cannot match response with open request, ignoring
qt.modbus: (RTU client) Cannot match response with open request, ignoring

is it problem of connection or I need to check crc by myself?

J.Hilk

@Pavel-Romankov what version of Qt ? and are you sure the slaves calculates the correct CRC?

Can you verify with a 3rd party tool ?

Pavel Romankov

Qt 5.11.3
I receive data from different devices and problem is everywhere.