Suggestion : Allow for MQTT topic assigment for attributes in objects

[analystcmyk]

Running Version 0.7.0-rc6

I have an object defined as :

{"page":0,"id":5,"obj":"bar","x":0,"y":30,"h":30,"w":100, "min":0, "max":100,"val":22}

I can change the text by publishing raw value 88 via MQTT to topic hasp/plate/command/p0b5.val

My sensor publishes every 5 seconds a raw temperature value to sensor1/temp

Suggest

Allow for topic to be added directly to the object.

{"page":0,"id":5,"obj":"bar","x":0,"y":30,"h":30,"w":100, "min":0, "max":100,"val":{"srctopic":"sensor1/temp"}}

The "val":{"srctopic":"sensor1/temp"} would mean that published value in the srctopic would set the value.

This would save a lot of workarounds like mqtt-mqtt republishing, and in the case of multiple devices would ease the effort of configuring.

A lot of smart devices eg the ones flashed with OpenBeken https://github.com/openshwprojects/OpenBK7231T_App publish directly any value there.

Questions

• topic should be within same broker? If not it would mean a lot of extra work, or
  complex syntax like user:passw@mqtt://topicpath/:1883
• limit to read published values only?
  Or allow actions to publish to custom topics as well?

Any thoughts would be appreciated.

[smcgann99]

The main issue I can see is why should val be treated differently to other objects?
What I mean is that it would also be nice to apply this function to a text property or a switch toggle state etc etc ....
I haven't used OpenBK but in the case of Tasmota for example you could easily get the device to publish the value to the hasp topic directly.

[analystcmyk]

I'll try with OpenBEKEN.
Espurna afaik does not support specific values to be published in a different topic.

[analystcmyk]

OpenBEKEN can handle it with this command.

addEventHandler OnChannelChange 2 publish hasp/plate/command/p0b5.val $CH2 1

Nevertheless you are not always in control of the topic (third party devices etc), so it still might be something to consider.

And yes I like your suggestion to not only allow that for val, but for any variable. That would allow for example to autoscale objects or ranges:

{
  "page": 0,
  "id": 5,
  "obj": "bar",
  "x": 0,
  "y": 30,
  "h": 30,
  "w": 100,
  "min": 0,
  "max": {
    "srctopic": "sensor1/maxtemp"
  },
  "val": {
    "srctopic": "sensor1/temp"
  }
}

[smcgann99]

The "val":{"srctopic":"sensor1/temp"} would mean that published value in the srctopic would set the value.

It's not just the topic but also the payload property to use, so not quite that simple.
It would also potentially add a lot of additional subscriptions to the device, which impact memory and performance.

[fvanroie]

This is typically the function of an Home Automation System, to keep tabs on all devices and convert topic/payload/protocol where needed. This should not be the functionality of a display-controller.