[SOLVED]MQTT 1.x follow channel

Add-ons Bindings
1

Hello,

Here is the things, I have an item that is polling its value from a modbus sensor and I would like to forward that value to a MQTT broker using the follow profile and the MQTT 1.x binding. It seems to connect to the broker but not to send the correct payload.

Number TemperatureKMInt16            "[%.1f °C]"    <temperature> (Room001)    { channel="modbus:data:PLCTCP:holding:temperatureKM:number", mqtt=">[mybroker:modbus/temperature:command:*:JSONPATH($.Temperature)" [profile="follow"] }

I would like the JSON payload to be:
{“Temperature”: 24.2}

Any idea of what am I doing wrong ?

thank you in advance

2

As I understand it, the [profile="follow"] part would require you to specify another Item to follow - so I don’t think that does anything at all here and can be left out.

mqtt=">[mybroker ... should be sufficient to what you want, but I know nothing of configuring MQTT 1.x

3

I do.

First, use the state instead of command.
Second, the JSONPATH transform only works one way. You can’t do it this way.
You will need to use a JS transformation

tojson.js In transformation folder

(function(temp) {
    return '{"Temperature":' + temp + '}';
})(input)

Your item:

Number TemperatureKMInt16            "[%.1f °C]"    <temperature> (Room001)    { channel="modbus:data:PLCTCP:holding:temperatureKM:number", mqtt=">[mybroker:modbus/temperature:state:*:JS(tojson.js)" }
4

Well, well well, I really through that it would work but it doesn’t and I don’t know why. It should.
Maybe I am now on 2.5…

You are going to need a proxy item young man

5

Actually I’ve found a solution using version 2 that adds mqtt as a channel. I don’t know why it did not get to my mind yesterday. Way easier !!!

Need to add a mqtt Bridge thing with channels and commandTopic. Then add an item and the correct channel, in order to format to json, there’s the Format before Publish feature that allows that.

6

Yes, good find. well done