Response address xxx is different from request address 33

[Syavash-kazemi]

Hi, I am trying to read some Modbus addresses from a multi-transducer through a serial port. I am running a loop to get around 5 readings per second.

Here is a snippet of the code:

    try:
        # Connect to the slave
        master = modbus_rtu.RtuMaster(
            serial.Serial(port=CONFIGS["PORT"], baudrate=CONFIGS["SERIAL_BAUDRATE"],
                          bytesize=CONFIGS["SERIAL_BYTESIZE"], parity=CONFIGS["SERIAL_PARITY"],
                          stopbits=CONFIGS["SERIAL_STOPBITS"], xonxoff=0)
        )
        master.set_timeout(0.5)
        master.set_verbose(False)
        logger.info("connected")
        LOGGER_MTR.debug("modbus slave connected")

        while True:
            utc_now = datetime.utcnow()

            master.open()
            try:
                frequency = master.execute(slave=CONFIGS["MODBUS_SLAVE"],
                                           function_code=CONFIGS["MODBUS_HZ_FUNCTION_CODE"],
                                           starting_address=CONFIGS["MODBUS_HZ_STARTING_ADDRESS"],
                                           quantity_of_x=CONFIGS["MODBUS_HZ_BYTES"])
                frequency = unsigned_measurement_to_float(frequency)
            except Exception as try_error:
                LOGGER_MTR.error("failed reading from slave")
                LOGGER_MTR.error(try_error)
                frequency = None
            master.close()

            time.sleep(0.15)

So the loop works well and I get readings. However, sometimes I get the next error (this is just an example) for some minutes, before coming back and streaming values again:

...
failed reading from slave
Response address 193 is different from request address 33
Freq: None
failed reading from slave
Response address 193 is different from request address 33
....

So MODBUS_SLAVE is 33, but I don't understand why the master is calling the address 193. I have seen any number being called between 1 and 255.

Am I missing something? What could it be the reason to end up