writing registers with modpoll - how to do....? ...reading works fine ! about modpoll

[gavinying]

Hi, the holding_register writing function can be achieved via MQTT publish, take the online modsim as an example, when you run modpoll with MQTT broker specified,

modpoll --tcp modsim.topmaker.net --config https://raw.githubusercontent.com/gavinying/modpoll/master/examples/modsim.csv --mqtt-host mqtt.eclipseprojects.io

the tool will automatically subscribe to the topic modpoll/modsim001/set, so if you want to write to a specific holding_register, you can use any MQTT client tool, like mosquitto-clients or MQTTX, publish the following message to the target device's topic, e.g. modpoll/modsim001/set for device modsim001,

{
  "object_type": "holding_register",
  "address": 40001,
  "value": 12
}

Attention: you need to keep the modpoll tool running (subscriber) while you publish new values, open a new terminal, here is an example command using mosquitto_pub,

mosquitto_pub -h mqtt.eclipseprojects.io -t modpoll/modsim001/set -m "{\"object_type\":\"holding_register\",\"address\":40001,\"value\":12}"

After the message succesfully published, you will see the value changed in modpoll output.

Hope it helps.
Thanks for your interest for modpoll. Cheers.

Gavin

[gavinying]

BTW, you can find more details here in README.

[pythonlubo]

Hi Gavin, with your documentation i've no positive result on my RPi-system....

now I've check what journalctl says to published messages on the modpoll RPi.....

My Inverter has a Remote Shutdown Register : {"object_type": "holding_register", "address": 420, "value": 0} to swich off (..and "1" for on)

Modpoll has in .csv the lines:

---

device,wr1,1,,

poll,holding_register,400,50,BE_BE

ref,rs1,420,int16,rw # ( rs1 means remote switch 1 )

---

In mosquitto broker will publish the register in /hs36/wr/wr1/rs1/"1" (...for ON)

...works fine....

Now I published with mosquitto_pub from an other system:

mosquitto_pub -h xxx.xxx.xxx.xxx -p 1883 -t /hs36/wr/wr1/set -m "{"object_type": "holding_register", "address": 420, "value": 0}" #...for shut down the inverter...

journalctl shows an error:

Fail to parse json message: b'{object_type: holding_register, address: 420, value: 0}'

---

If I give the message without " ---- -m "{.........}" as {....}

Error Message from mosquitto:

Error: Unknown option 'holding_register,'.

---

If I give the message with -m '{....}'

It will break the modpoll completly....

AttributeError: 'ModbusIOExeption' object has no attribute 'function_code'

---

...what other solutions I've to test....?

Thanks for help....

[pythonlubo]

Hello again,
the right mosquitto_pub line is:

mosquitto_pub -h xxx.xxx.xxx.xxx -p 1883 -t /hs36/wr/wr1/set -m '{"object_type": "holding_register", "address": 406, "value": 1}'

(for example)

In journalctl i've see that the message arrive....after polling all csv-lines modpoll give the message:

• Writing Register(s): device=wr1, address=406, value=1 -

...after that modpoll stops with errorcode:

return.result.function_code < 0x80
AttributError: 'ModbusIOException' object has no attribute 'function_code'

My Inverter need to write a register the functioncode 10H .....

modpoll has the possibility to give the function_code "10H" to the inverter ?

Thanks a lot.....

[gavinying]

Yes, modpoll does support "10H", which writes mutiple registers, but in your case, looks only writing a single register, which shall use function code "06".

In fact, modpoll supports the following function codes, fyi.

• read coils (01)
• read descrete inputs (02)
• read holding registers (03)
• read input registers (04)
• write single coil (05)
• write single register (06)
• write multiple coils (15 or 0x0F)
• write multiple registers (16 or 0x10)

Can you share the complete logs? including the command you used to start modpoll for further investigation.

[pythonlubo]

...now I try "minimalmodbus" to write the Inverter registers - it works fine....

The correct "minimalmodbus"-Line here is:

instrument.write_register(324, 560, 0, 16)

324 is the registeraddress
560 is the value without decimal - means 56.0 Volt finaly
0 - i dont know for what....
16 is the right command to write the register

I think modpoll should use the "16" command to write - not "10" or "6"....
Ii it possible to advise modpoll to use the 16 command for writing registers...?
tks.....

[gavinying]

Close it due to no activities for long time.