Is it possible to connect thing's channel with follow profile to a group item?

  • Platform information:
    Release = Raspbian GNU/Linux 9 (stretch)
    Kernel = Linux 4.19.66-v7+
    Platform = Raspberry Pi 3 Model B Plus Rev 1.3
    openHAB 2.5.1-2 (Release Build)
  • Issue of the topic:
    I am trying (using Paper UI) to send the result status ON/OFF of a group of switch items to a KNX channel using a follow profile. When I link the same channel of the KNX device to single switch item with the follow profile, it works as expected. However when I link the channel to the group, no communication is sent to the KNX bus.

Is it by design, or am I just doing sth wrong?

I’m not sure you’ve grasped what the follow profile does.
It takes an incoming channel (incoming only) which would normally update the state of the linked Item. But instead, it issues a command to that Item instead.

So if we link a KNX channel with follow profile to a Group Item, it should in theory issue a command to the Group when an incoming KNX message arrives.
Group states never respond to commands - they are only updated by the member aggregation function, if defined.
Group will pass on an incoming command to all member Items, as a command.

It sounds like you want to send the Group state to KNX ?
I don’t think theres any direct way to do that, but it’s easy to create an interim Item linked to your KNX channel and have a rule triggered by group state change that sends command to interim Item.

EDIT - Maybe there is a direct way. I don’t know if it would work, but if you use a control-xxx type KNX channel it works “backwards” - normally used to make incoming messages as commands, but also takes openHAB Item state changes and sends them out over KNX.
It’s very rare to link a Group to any channel … you don’t usually get any useful functionality.

A - Thanks for extra explanation of the follow profile, you got it right with the grasping.
B - I’ll look into the KNX control type.
C - I did think about creating rules, but my initial grasping of the follow profile looked like to quicker alternative.
D - I see 2 possible applications, if this is achievable:

  1. Sending On/Off to KNX actuators based on logic from multiple motions sensors from different bindings.
  2. Sending an avarage of temperatures form multiple sensors to a signle thermostat without additional rules.
    Both are achievable with rules, however so far I was only using the Paper UI experimental rules, which are a nice feature if you want to sequence multiple actions with simple trigger/condition. But if i’ts a simple action, but more complex logic they are a little troublesome. Maybe the trick is in combining both groups and rules.

In most cases like that, you end up wanting to do extra stuff like varying the response by time-of-day or adding timing functions. i.e. work for rules

This is a powerful technique.

I did try your proposal. The result is the same as previously.

Anyhow, moving on to learning more about rules.

Thanks for the suggestions.