Sending time on MODBUS TCP, setting MSB and LSB

Configuration
1

My ventilation system doesn’t have a very accurate clock, but the time can be set using MODBUS. I’m trying to figure out how I can send the hour and minute in the following format:

image
image872×48 7.13 KB

My current script looks like this:

alias: Komfovent set current time
sequence:
  - service: modbus.write_register
    data:
      address: 28
      hub: komfovent
      unit: 1
      value: "{{ now().timestamp() | timestamp_custom('%H%M') }}"

But this number, e.g. 1215, gets converted to hex as a whole, so the result becomes: 4BF, but the correct value should be 0C0F (0C = 12 and 0F = 15)

How can I do this with a template?

1 Like
2

Hopefully someone can help with a template, but if I could make a suggestion - why not do it in Node red? Would be easy to do and you could schedule a clock update for every 10 minutes or longer, depending on how badly your ventilation system drifts so you are not writing to that register every few seconds.

3

My goal is not to write to the register every few seconds, but once a week. And that can easily be scheduled in Home Assistant as well.

4

Just spilt them ??

{{"%02x" | format( (now().timestamp()| timestamp_custom('%H'))|int)+ "%02x" | format( (now().timestamp()| timestamp_custom('%M'))|int)}}
5

I also stumbled on this in another topic, where msb and lsb are actually split :thinking:

  - service: modbus.write_register
    data:
      address: 28
      unit: 1
      hub: komfovent
      value:
        - '{{ "%02x" | format( (now().timestamp()| timestamp_custom('%H'))|int) }}' #msb
        - '{{ "%02x" | format( (now().timestamp()| timestamp_custom('%M'))|int) }}' #lsb

And shouldn’t it be address 29 (as shown in your screen shot :thinking:)

6

I still haven’t been able to figure this out, but instead resorted to setting the time to 0:30 every Monday.

alias: Komfovent reset time 0:30
sequence:
  - data:
      address: 28
      hub: komfovent
      unit: 1
      value: 30
    action: modbus.write_register
mode: single
description: ""

Documented here: (Re)set the time on our Komfovent ventilation system :: Cavelab blog — Stories from the Cavelab

Modbus addressing in Home Assistant starts at 0, but the document starts at 1.