read_holding_registers returns None

[al37919]

I show a minimal code example indicating problem and output which I receive using pymodbus-1.2.0 and pymodbus3-1.0.0. to_string() is omitted for clarity. It's just a magic function to convert array of registers to a readable string. The question is why read_holding_registers() returns None when using pymodbus3?
Thanks

#! /usr/bin/env python3

from pymodbus3.client.sync import ModbusSerialClient as ModbusClient

pymc = ModbusClient(method="ascii", port="/dev/ttyUSB2", baudrate=9600, timeout=0.25)
ret = pymc.read_holding_registers(0x130, 13, unit=1)
print(ret)
print(to_string(ret.registers[1:]))

pymodbus-1.2.0 response:

ReadRegisterResponse (13)
Meradat-VIT19IT1

pymodbus3-1.0.0 response:

None
Traceback (most recent call last):
  File "./test_pymodbus3.py", line 33, in <module>
    print(to_string(ret.registers))
AttributeError: 'NoneType' object has no attribute 'registers'

[pikowai]

Had a similar issue which was solved by adding sleep(1) to give the slave time to respond, would be interested to see if this helps.

…

On Tue, Feb 28, 2017 at 2:19 AM, al37919 ***@***.***> wrote: I show a minimal code example indicating problem and output which I receive using pymodbus-1.2.0 and pymodbus3-1.0.0. to_string() is omitted for clarity. It's just a magic function to convert array of registers to a readable string. The question is why read_holding_registers() returns None when using pymodbus3? Thanks #! /usr/bin/env python3 from pymodbus3.client.sync import ModbusSerialClient as ModbusClient pymc = ModbusClient(method="ascii", port="/dev/ttyUSB2", baudrate=9600, timeout=0.25) ret = pymc.read_holding_registers(0x130, 13, unit=1) print(ret) print(to_string(ret.registers[1:])) pymodbus-1.2.0 response: ReadRegisterResponse (13) Meradat-VIT19IT1 pymodbus3-1.0.0 response: None Traceback (most recent call last): File "./test_pymodbus3.py", line 33, in <module> print(to_string(ret.registers)) AttributeError: 'NoneType' object has no attribute 'registers' — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#3>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ATosu5OBfkIFSxSrqw_EQRBOe8sd5A8lks5rgs1vgaJpZM4MNGA8> .

[al37919]

unfortunately, time.sleep(1) between ModbusClient() and read_holding_registers() doesn't help.
The response stays None

[pikowai]

try after read_holding_registers() i.e. client = ModbusSerialClient(method='rtu', port='/dev/ttySC0', timeout=1, baudrate=115200, retry_on_empty=1) res = client.read_input_registers(0x3100, 8, unit=mb_address) time.sleep(1)

…

On Thu, Mar 2, 2017 at 10:38 PM, al37919 ***@***.***> wrote: unfortunately, time.sleep(1) between ModbusClient() and read_holding_registers() doesn't help. The response stays None — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#3 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ATosu9p-7Nag0oW4NQD5k6pF-uuR_35eks5rho4TgaJpZM4MNGA8> .

[perkarlberg]

I experienced the issue you are describing (serial client returning None when reading registers), when using pymodbus3 installed via pip. When instead running a (newer) version cloned from master, the issue was solved.

I think this was addressed in #5.

[HeathKang]

I used @perkarlberg way, and succeed!
In pypi.python, pymodbus3 1.0.0 was uploaded on 2014-07-18, and #5 was merged on 04-04, so I think you had install a old version by pip.

[eterey]

Fixed now,