OH3 - mqtt common channel for state and command

Add-ons Bindings
,
1

Hi,
since upgrading to OH3 from 2, I’ve encountered following problem;

Thing topic myTopic "My Topic" {
        Channels:
            Type number : myNum "mynum name" [stateTopic="smth/smth/one", commandTopic="smth/smth/one"]

and Item

Number myNum "mynum name" (Group) {channel="mqtt:topic:broker:myTopic:myNum"}

This combination unfortunately does not work anymore, I have to manually create two channels and connect them both to my only item. I want to read and command the same topic through one item.

I wonder why this does not work in OH3 anymore? Why do I have to create two channels? I got it into a working state, but it’s rather unfortunate and too much repetitive code to create two channels when one is enough, especially when I need to handle like 100 or more items like this.

Maybe there is just a change in the syntax, but I didn’t find any info about that.

Thanks for any reply.

2

Why not? What happens? Can you show a log extract?

(Note that it is considered unusual to use the same topic for state and command messages in MQTT)

3

There is nothing in the log. No error, it just does not work. I noticed it takes the first topic, either state or command, that works just fine, but the other one gets ignored. So when i have

stateTopic=“smth/smth/one”, commandTopic=“smth/smth/one”

I can succesfully read from the topic, but cannot change the value on broker via this item.

4

This is bonkers. You do understand it risks creating a loop?

How exactly are you attempting to do that? How are looking at what the broker receives? Is it just openHAB using this topic for now, no other device yet?

5

+1

You have given an XY problem that is a little silly for home automation.

What is happening is you are sending a command to the topic then openHAB is reading that state and sending it into a loop.

The way to stop this from happening is having 2 topics.

Lets say the number is the set temperature of your HVAC device.

You have a stateTopic and a commandTopic.

Lets say topics are bedroom/aircon/state and bedroom/aircon/command

You have 3 devices connected to MQTT that want to change the temp they would do this by sending the number to the bedroom/aircon/command topic then the HVAC would receive the command and only the HVAC will publish to the bedroom/aircon/state topic.