Basic mqtt channel problem

Setup, Configuration and Use Beginners
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  • Platform information:
    • Hardware: Generic Server
    • OS: FreeBSD 13.0-RELEASE-p5
    • Java Runtime Environment: openjdk version “11.0.13” 2021-10-19
    • openHAB version: openHAB 3.2.0
  • Issue of the topic: basic mqtt channel problem
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I’m trying to use Openhab3 to visualize some measurements. These measurements come via mqtt in two different formats:

Payload Type1

Topic is "xxx/c052719c-29a7-a6d4-bfe5-0b96027cfaec
payload is {“id”:c052719c-29a7-a6d4-bfe5-0b96027cfaec,“value”:3.45,“ts”:1643887734}

I created a mqtt binding and a channel, used a incoming transformation “JSONPATH:$.value” and everything works fine.

Payload type 2:

Topic is “xxx/01af17b2-a448-474c-787a-44014b091067/channel_1”,
Payload is “123.45”

I’m trying for hours to get this payload into Openhab3. I left everything on default, “Incoming Value Transformations” is left empty. The thing shows “online”, but no values are coming. What did I do wrong?

Martin

PS. This is the channel code:

UID: mqtt:topic:mosquitto_birdland:f65944decc
label: Sensor Channel 1
thingTypeUID: mqtt:topic
configuration: {}
bridgeUID: mqtt:broker:mosquitto_birdland
channels:

  • id: sensor_channel_1
    channelTypeUID: mqtt:number
    label: Channel 1 Temperatur
    description: “”
    configuration:
    formatBeforePublish: “%s °C”
    stateTopic: xxx/01af17b2-a448-474c-787a-44014b091067/channel_1
    unit: °C
2

Try a brand new Channel, but use a String Channel, and link it to a String thing. Don’t add fancy units, or formatBeforePublish. See if that works first.

1 Like
3

What have you linked your channel to, i.e. Item type?

Background - at OH3.1, units on incoming MQTT messages were not applied, the channel’s “unit” was only tacked on to outbound messages.
I know there was some interest in enhancing that so that “unit” got tacked on to incoming messages as well, but not sure if that got included in OH3.2

4

It did not but I’m pretty sure it’s in OH 3.3 M1.

5

Thank you for your input. I created a new thing with a channel “channelTypeUID: mqtt:string” and that delivered the value from the mqtt message.

I don’t understand at this time why this value isn’t saved and I can’t see the graph over the time. I created a item type Number:Temperature for one of the sensors that send JSON messages and this gives me a diagram of the historic values.

Martin

6

What value? Is this an Item, what Item type? String type Items cannot be charted’

So, that’ one is working fine then, yes?

7

Yes, the Number:Temperature item works fine. The MQTT message in JSON format gets decoded and the values charted. Now I’m trying to get the other kind of MQTT messages to work.

Can I set the loglever higher to see the workings of the MQTT message processing?

Update: Changed the (now working) item for the non-JSON message from “string” to “Number:Temperature”. Stopped working… don’t understand why. Obviously something like “22.33” as payload in the MQTT message is recognized as string, but not as number.