Connecting an existing KNX installation to Home assistant without ETS

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I am sharing this post as I didn’t really find anywhere a proven solution that would allow to connect an existing KNX setup to Home Assistant, without access to the original ETS project. Hoping that it might be useful to other people.

The existing installation

I recently moved to an apartment built about 15 years ago with an existing KNX setup. The original installation was done so that it could be controlled by calling some phone number and pressing some keys on the phone keyboard.
But who has a landline nowadays…

Since I moved I have always wanted to connect it to my existing Home Assistant platform but I didn’t have access to the ETS software or to the ETS project that was setup originally.

The initial idea

After some initial research I realized that the “official” way would be to buy a KNX interface or router and connect it to my network via ethernet. Some of them can be powered via the ethernet port and don’t require addition power supply. The problem is that

  • my router is far from my cabinet with the KNX devices and running an ethernet cable between the two would have been quite complex
  • an IP interface or router is quite expensive (about 170€ for some entry level ones)

I also read in some threads that there might be a need to register the IP interface in the ETS software but wasn’t entirely sure if it would be the case.

The final solution

After more research, I realized that busware.de developed the TUL board based on ESP32 that can connect to an existing KNX setup and be connected to home assistant via WiFI. The TUL board can’t be powered by the KNX bus though and needs to be powered from its USB-c port.

I just bought one, connected it, and it just worked! After flashing the TUL and setting up KNX in Home Assistant following the official integration I was able to listen to the KNX traffic from Home assistant.

I originally powered the TUL from a power bank as I didn’t have access to a power plug next to my KNX connections, but I then moved to powering it directly plugging it to 12V DC transfomer in my KNX cabinet.

In the end what I needed to buy was:

  • a TUL device from busware
  • some KNX bus cable to connect the TUL to the KNX bus using the black/red wires (I originally tried to use standard stranded wires but those don’t really work when connecting to KNX bus connectors) – I just needed 20 cm but couldn’t find any place where I could buy less than 5m
  • a 12V DC red/black to 5.5V DC USB-c transformer (like the ones used in cars) to power the TUL from my cabinet

With all that, I was able to listen to events on the KNX bus and retro-engineer the devices I need to setup

The Home Assistant setup

On the Home Assistant side, after having connected the TUL by providing its IP I checked the “KNX” > “Group Monitor” tab to listen to the messages being sent when I was pressing buttons on switches/controllers in the apartment.

I realized that my lights and electrical blinds don’t seem to be connected to KNX but that all my climate control devices are.

I was then able to map the AC controllers and KNX addresses to the sensors in my home. Here is an example for the AC controller in my living room.

knx:
  sensor:
    - name: "Temp Living"
      state_address: "1/1/6"
      type: temperature
      sync_state: 3
  number:
    - name: "Temperature threshold Living"
      address: "1/1/7"
      state_address: "1/1/7"
      type: temperature
      min: 18
      max: 23
      step: 0.5
      mode: slider

And with this, I am now able to see the temperature in the different rooms and set the threshold for those. This then triggers cooling/heating automatically.

Also, in my case, if I update the temperature threshold from the physical controllers, it gets updated automatically in Home Assistant, but your mileage might very much vary based on the existing KNX configuration.

With this setup I can now automate changing the threshold based on some rules or from my phone when I am not at home.

Conclusion

It is possible to connect an exisiting KNX setup to Home Assistant without access to the ETS project using a TUL from busware and connecting it to both the KXN bus and an existing WiFi.

This won’t give you the full power of KNX automations, but it can allow people to interact with existing KNX devices and sensors from Home Assistant.

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2

Hi

Thanks a lot for the share and can be a good solution for existing KNX installations you just need to interface with HA and that you don’t have ETS project files.

Vincèn

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Great solution without getting too deep into KNX. If you know the installer, there is quite a good chance they can give you the file and a Report of all the Group Addresses used.
You could have gone the official route and used an IP interface. Most of them are powered by the Bus itself and can be put wherever you have a KNX Cable connection. For example this one. You can also look for them used. They are usually quite cheap when used.

Then you could use a ETS 6 Demo License (free) to configure the Interface and import your Group Addresses. Or if you have a friendly electrician they might even be able to lend you the Professional Dongle.

If its a rented condo you might even be able to convince the owner to reimburse you for the interface. If its your own, I would make an effort to have a full KNX Project file so any further work on the whole system is much easier.

For the server you should find out which one it is. When you say calling them prominently the Gira Homeserver comes to mind.

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Hi :wave:!

This is in fact the only interface I’d not recommend to buy for use with HA. It has several bugs regarding Knx Secure which may lead to confusion at some point.
There are better ones for a similar price. I have good experience with Enertex, Weinzierl or Gira devices.

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