Minimum KNX set-up?

I realised the other day that I have a KNX interface for the ConfoAir350.
Now I am wondering, what is the minimum set-up to integrate KNX with OH?
Can imagine I need a gateway of sort?!
Aha, did some reading… a gateway is needed… saw the binding for it…
Would most likely build one myself…
May even use other KNX devices…

Does the KNX network have to be on a different IP, or can it be on the same network as the rest of the home.

Any advice from people who have a KNX network, what the best way forward would be?
Pit falls; issues, gotchas?

Any hints appreciated.

I believe that the answer to this is:

  1. A KNX TP - UART (Twisted Pair - Universal Asynchronous Receive Transmit)
    One option is the TPUART USB Adapter, another the TPUART Bluetooth Light and finally there is also the Pigator Stuff [Link 1 2 3 4]. Some newer options include: ESP based TPUART solution

  2. KNX Bus Twisted Pair Wires (2x2x0,8mm) + KNX Bus Power Supply (24-30V DC)
    I believe that you will need to provide Power to the Bus, even if you connect only 1 endpoint (the KNX interface on the ConfoAir350). Other opinions are needed here… @george.erhan @Udo_Hartmann

  3. A network gateway daemon on your Linux host to handle comms between the 2 interfaces (IP & TPUART): KNXd is what people use the most with the TPUART

  4. The KNX Binding of course :slight_smile:

If you build a low cost (but reliable solution) using one of the 2 TPUART interfaces, you don’t have an IP involved.
You will use a Raspberry Pi to connect with either USB or BT to the KNX Bus.

There are more expensive options with IP Gateways of course. In this case, it is recommended (but not needed) to create a VLAN to seperate the KNXnet/IP traffic from the rest of the IP traffic. I would say that this is good from a security perspective, not so much functionality. The communications will work without any problems even if you keep everything on the same (V)LAN/IP Subnet/Broadcast domain.

Start low cost (I would say the USB UART for higher reliability, but I also I like the new Bluetooth TPUART which is Bus powered but it adds a small delay in the comms :frowning: )

You can’t go wrong with KNX (although it’s an old protocol with only 9.600bps)… it is very stable and reliable (if deployed correctly) and I don’t see any big challenge (cost of devices is an issue but this goes down over time)


Thank you kindly for this comprehensive response… I do appreciate it… exactly what I was after… this I understand :slight_smile:
Still reading… researching… :slight_smile:
Looks like others like your post too, given the number of link visits already…

1 Like

I had in my to-do list an entry titled: "create a How-To connect openHAB to the KNX world with ALL possible options"
I think that you helped me to kick start it :slight_smile:
There are more options (IP Interfaces, IP Routers, etc, etc)

1 Like

Hi @Max_G,

The minimum setup needed for a KNX system consists of:

  • 1 KNX power supply with a current rate depending on the number of devices in the KNX network (ranging between 120 mA and 640 mA) - the KNX standard rates a maximum of 10mA per KNX device. So, depending on the number of devices you can have a maximum of 64 devices per KNX TP line.
  • 1 KNX/IP gateway/router. This can be bought from a producer as a standalone device, or as @Dim suggested you can buy a tpuart USB adaptor and use knxd or eibd for setting up a software ip gateway/router
  • KNX devices for interfacing with other systems, switches, sensors, thermostats, etc.

For a production environment I definitely recommend using a standalone IP router manufactured by a KNX certified producer.




I definitely agree with this statement.
That’s why for my own setup (not very large… 40 Switch actuator channels and 12 Shutter actuator channels), I didn’t go the DIY way and I bought the GIRA KNX/IP Router. There are many manufacturers out there. One good option is: MDT

George’s list is more accurate also. The items 1 & 3 in my list are basically a “DIY / home-made” KNX/IP gateway.
The KNX/IP gateway can be either a standalone device (like the GIRA) or a “construction” of hardware (TPUART+Raspberry) and software (knxd) components

I agree with @Dim and @george.erhan about the KNX components involved. Most of my KNX parts in my house are MDT, but i also have Busch/Jäger, ABB and others installed - that’s one of the beauties of KNX - mix and match as you see fit, they all speak the same (admitedly old but reliable) language.

My KNX components do their work independently (another beauty - KNX is decentralized), but openHAB makes the cherry on top, interweaving KNX with all the other components, that’s where smart home starts :slight_smile:


Well, I owe a knx System, and I like it very much. But there is a big con, that is, you will need to use ETS to configure knx. Of course, with a minimal knx system, you could use the free demo version, but I’m not sure if programming of devices is possible with the demo version, and if you want to use more than 5 devices (openHAB does not count as a device), you will have to use lite version for 200 € (20 devices maximum). If this is not enough, ETS professional price is 1000 €, that’s… really… :frowning:
You should use knx certified cabling, at least, if wiring the whole house, simply because it’s very easy to recognize the green cable.
Of course, you could use any shielded twisted pair, best practice is black and red wires, because each device has a black and a red clamp (see picture above).
Be aware that knx wires are knx exclusive, so you must not use other pairs of wire from the same cable for other purposes, so knx is mostly interesting when planning to build a house or when rewiring the house.

1 Like

It was a challenge for me originally to learn how to use ETS but I haven’t used it for a long time now.
I reprogrammed every device in my house when I moved in because the original installer made a mess and since then I haven’t changed my configs. Of course, I haven’t added any more endpoints since the original installation so it was not really needed.

The cherry on top (openHAB2) allows me to play as much as I want with KNX without touching ETS :slight_smile:

Agreed… but there is always google… :wink: (search string: ETS 5.0.5)

To be honest: Just for interfacing this one device it is an overkill.
KNX is an option when rewiring complete buildings, as a small solution for just one device one must decide if it´s worth the effort. And just because there is a knx interface in the device, it might not be the easiest solution (see below)

You´d require an IP-Interface (A PI with e.g. Pigator should work), a knx power supply for the bus, some knx cable plus, and that´s the most expensive part, the ETS software (Min 200€). There is an option to use ETS Demo (5 devices, free), details here.
Overall, with used components in a dirty hack, I´d estimate 300 Euros.

There is a solution for FHEM, that utilizes the built-in serial port. Maybe interfacing there is the better way (How about an ESP ?)

And finally there is a binding for openHAB as well, see
this page, it may have what you need.

Hope I could help,


I understood that hint, but I don´t like it. :smirk:
There is a demo version (5 devices) for free, if you need some more devices it 200€ and if you plan a professional setup with more than 20 devices you should buy the software for 1000€. Compared to the costs for a complete knx setup in a house or even building a house from scratch theses costs can be considered “minor”.

I don´t like the pricing model of the knx foundation, but if this does not fit one could go for other solutions.


When I bought the Zehnder 350, I had to make a quick decision about which controller to buy.

The idea was to integrate and control of the 350 via OH alone; so there is no Zehnder wall controller for the 350. I thought it was redundant, because the posts I read on this forum indicated there is no need for it.
When I was reading I saw quite a few issues with the serial interface, and decided to use KNX, without knowing what else would be involved… this seemed to be a mistake in hindsight, but with this post, and only this 350 to be connected, I know now which route to go.

While I appreciate standards, there is an extra cost for bearing the KNX logo (and associated licensing), and worse, the ETS software requirement and cost. In my books they are fools; had they provided the software for free the uptake of KNX would be higher. One reason why I have no desire to use more KNX devices.

By the way, the KNX protocol is easily replicated with MQTT – as far as I understand the structure of KNX.

Anyway… keep it coming :slight_smile: – thanks for all the input.

Correct. I actually paid the entire amount for the Pro license and I recommend the same.
If someone wants to do a pilot/test lab (not production)… he could use google :stuck_out_tongue:

Also correct that putting together a KNX Bus for just 1 endpoint it’s an overkill. Much better to interface to the existing serial port.

I don’t know about that… KNX is a proprietary / closed system and it is complex (according to my understanding).
KNX Telegrams are not very similar to the MQTT messages (and the architecture is different)

Don’t agree on the ‘minor’ in cost… I actually do not want to know what my to be system would cost if I were to use KNX controllers.

I am in the process of designing the control boards (drivers) for the LEDs in the house – all dimmable, as I augment internal lighting based on external ambient light levels (with OH based on time of day). I’ll get the boards manufactured in numbers, keep a few and sell the rest.

The house is all Ethernet, hence, why I would not like another cabling type to be installed.
I will have room speakers with individual little amplifiers, getting digital streams.
I am even considering building an Arduino UNO board with Ethernet on board, including PoE… as there is no such thing, because most go wireless.

I wasn’t clear enough, you could set-up a message structure like blah/blah/3/4/10/3 in MQTT mimicking the KNX command structure; yes, understood different everything.

1 Like

If you think about it: Normally, the ETS license cost is born by the KNX certified installer who “subsidizes” the investment over time while he deploys KNX installations for the end-Customers.

We (as end-Customers) are not the main target group of the KNX association and we are not “supposed” to use ETS :slight_smile: (in theory we should call the installers to modify the configs).

Of course, this does not apply to openHAB users who are going to scratch the surface of any system :smile:

Back to the original min KNX setup discussion (I also don’t agree with the KNX association policy but I can’t change it… of course giving access to ETS for a lower cost to the end-Customer would increase the adoption)


To be honest, knx wasn’t designed for hobby but only for professionals. knx as a ISO/IEC standard (14543-3) is not proprietary nor closed, but ETS is.
I think, the idea was, to protect electricians against hobby enthusiasts. :wink:
The Database is encrypted and there is no way not to use ETS for configuration (well, you could use tebis instead, but you would have to use only Hager tebis devices, but you could reuse tebis devices with ETS later…)

knx, formerly known as EIB, was designed in the late 1970’s, so this is some sort of Methusalem soft/hardware. And now look at the possibilities, wide range of manufacturers and the evolution…

I did the electric installation myself (yes, I can…;)), so I saved much money (to pay knx…) and I bought the devices with a big discount, and my installation was about the same prize, as it would have been with a conventional installation, done from a professional, not to say, I got an old ETS license very cheap :slight_smile:

1 Like

Correct. I mixed ETS with KNX :stuck_out_tongue:

I think this might be what you are looking at building?

hi i buy one of this dongles but in ets5.5.2 not discovered
is it need any drivers?:pensive::pensive: