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I'm trying to write values above 1000 using the minimalmodbus library, but my code generates the following error:

Traceback (most recent call last):
  File "D:/Projetos/ON/HMI/modbus_tk_test.py", line 19, in <module>
    instrument.write_register(38, 1001)
  File "D:\Projetos\ON\HMI\venv\lib\site-packages\minimalmodbus.py", line 511, in write_register
    self._generic_command(
  File "D:\Projetos\ON\HMI\venv\lib\site-packages\minimalmodbus.py", line 1177, in _generic_command
    payload_from_slave = self._perform_command(functioncode, payload_to_slave)
  File "D:\Projetos\ON\HMI\venv\lib\site-packages\minimalmodbus.py", line 1250, in _perform_command
    payload_from_slave = _extract_payload(
  File "D:\Projetos\ON\HMI\venv\lib\site-packages\minimalmodbus.py", line 1776, in _extract_payload
    _check_response_slaveerrorcode(response)
  File "D:\Projetos\ON\HMI\venv\lib\site-packages\minimalmodbus.py", line 3436, in _check_response_slaveerrorcode
    raise error
minimalmodbus.IllegalRequestError: Slave reported illegal data value

If I use values below 1001 no error is generated. Here is my code:

import minimalmodbus
import serial.serialutil
import time

instrument = minimalmodbus.Instrument('COM4', 247, minimalmodbus.MODE_RTU)

instrument.serial.baudrate = 115200
instrument.serial.bytesize = 8
instrument.serial.parity = serial.PARITY_NONE
instrument.serial.stopbits = 1
instrument.serial.timeout = 1          # seconds
instrument.clear_buffers_before_each_transaction = False
instrument.close_port_after_each_call = False
instrument.precalculate_read_size = False
print(minimalmodbus._calculate_minimum_silent_period(115200))

while True:
    data = instrument.read_registers(38, 1, 3)
    instrument.write_register(38, 1001)
    print(data)
    time.sleep(minimalmodbus._calculate_minimum_silent_period(115200))

Any help is appreciated.

aldosola
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    It's not `minimalmodbus` complaining here, it's the device itself. Is that value scaled in some way? Do you have the device doc to know what its limits are? – Tim Roberts Jul 23 '21 at 19:07
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    As the error says `Slave reported illegal data value` it's the slave that does not accept the value, the problem is not in your code – from56 Jul 23 '21 at 20:12
  • Thanks, for the help. There was a bug in the device firmware. – aldosola Jul 26 '21 at 14:23

0 Answers0