Modbus write operation takes very long time

Configuration
1

Hi,
I have a central heating unit that speaks modbus (De Dietrich), and for the last 2 years I’ve been using Home assistant to poll its status (temperatures, operation mode) succesfully. However I have not been able to succesfully write modbus commands to it. Nothing seems to happen.
E.g. I have a Home Assistant script that looks like this :

service: modbus.write_register
data_template:
  hub: Waveshare
  unit: 10
  address: 15
  value:
    - 12

If I run the script, the script seems to ‘hang’ : when I get the scripts status, minutes after launching it, it is still ‘executing’.
There seems nothing usefull in the trace of the script, or the logging.

It seems very related to this topic.
Does anybody know how to solve it? I would like to avoid a 3rd party modbus library, as I think it might do some modbus ‘writes’ at the same time on my cyclic polling of some modbus registers, which might get things garbled.

PS regarding my example code : I know that in the last line, I should not use the syntax for multiple values, but this is to avoid a small modbus bug in my heater. See here.

2

up. no one?

3

Solved!
I had too many variables (15+), that I polled every 30s, with a 2s delay between each variable.
That’s why there was no ‘time slot’ available anymore to do the write commands.

I decreased the " message_wait_milliseconds", so that there was time available.
So now the write operation succeeds each time within 30s.

Would there be a way to have write commands take precedence over read commands, so that the reaction time of a user action is faster?