Qt C++：使用 Modbus RTU 类 (RS485) 从多个从站读取数据

Question

I tried reading values from 1 temperature sensor using Qt modbus class in the following way :

QModbusDataUnit(QModbusDataUnit::InputRegisters, /*startAddress*/ 1000, /*numberOfEntries*/ 1 );

Now what I want is reading values from different slaves ( different device ID's same port).

I tried pymodbus as its functions has device id argument (example : unit=0x03) :

result = client.read_input_registers(0x03E8 ,1, unit=0x03)

But I can't figure out how to do the same using Qt.

Any kind of help is appreciated.

Answer 1

That's not so straightforward as you might think and QtModbus is not very well documented but I think you need to do it in the query using serverAddress as your slave ID:

QModbusReply *QModbusClient::sendReadRequest(const QModbusDataUnit &read, int serverAddress)

See here for some (not much) more detail.