This page last changed on Mar 04, 2013 by hapmore.


For school I need to make some sort of home automation project. But I've got 2 choices.
I can use O.R. (open remote) to send KNXnet/IP to my gateway which sends KNX to my UART and arduino which then control my stepping switches.
I can use O.R. to send KNXnet/IP directly to my arduino which then interprets it and controls my stepping switches.

now for my questions.

  • What would be the best choice?
  • Is there a library from KNXnet/IP to KNX that I can run on my arduino (without using a gateway)?
  • Is there a way to interpret KNX directly on my arduino (without using an UART)?

that's it for now.
Thanks in advance.

Haven't heard of KNXnet/IP stacks for Arduino, so don't know if one exists or not.

Just curious why you've chosen to combine KNX with Arduino devices? Is it a requirement for your project? Using anything but KNX would simplify the task.

Posted by juha at Mar 05, 2013 17:14

The situation: In a house they have installed stepping switches to control the lights. We must make a system that controls these stepping switches maybe with openremote so we have chosen for the combination of Arduino and KNX because Openremote can send KNXnet/ip.

1. A possible way of or project is that we use a normal KNX system so with a gateway to receive the commands of openremote and use the arduino as a KNX module to control the stepping switches (

2. Another way is that we receive the commands of openremote with the arduino and use the arduino for controlling the stepping switches so that there doesn't have to be a gateway and maybe no knx-bus. So you can save money by buying an arduino instead of a gateway.

So these are the requirements. in the link of point 1 there is a library for arduino so maybe there is a way that we can add something to that to make point 2.

Posted by hapmore at Mar 06, 2013 13:04

What do you mean with stepping switches?
If you have KNX you normally have a KNX dim actuator and a KNX wall switch which sends the commands to the actuator.

Posted by mredeker at Mar 10, 2013 00:05

stepping switches, teleruptors,impulse switches like,or.r_qf.&bvm=bv.43287494,d.ZGU&biw=1525&bih=743&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=nRc9UcyeAbTe7AbUqICAAg#um=1&hl=nl&tbm=isch&sa=1&q=teleruptor&oq=teler&gs_l=img.3.0.0l10.151.3420.1.4993.,or.r_qf.&bvm=bv.43287494,d.ZGU&fp=270f3e8d4addcbbe&biw=1525&bih=743

so a pushbutton gives a pulse to the teleruptor an this switch on a lamp, there is not yet KNX in the house.
Butt openremote send only commands like KNX or X10 etc. And we need the arduino to recive the commands like an actuator.

Posted by hapmore at Mar 10, 2013 23:26

Referring to a myriad of switches and solutions does not really help to narrow down your problem. Actually it is unclear to me what your problem is, because you start with a half baked solution rather than with a design.
Getting back to your first post: You say this is a school project. Are using KNX and Arduino requirements given by your teachers? Must it be a real house installation, or does a lab setting suffice. Those issues determine your otions.


Posted by pz1 at Mar 11, 2013 09:40

Ok, so you don't have a KNX installation but you want to talk the KNX protocol to your arduino which then controls those propriatary devices.
We have a lot of users already who use TCP or HTTP to talk to arduino.

Why do you want to talk KNX if you don't even have KNX devices?

Posted by mredeker at Mar 11, 2013 09:45

In the first post we say there are 2 options and we must make a decision of which is the best. The goal of the project is that it works in a real home. We must use the Arduino to control the stepping-switches. And use Openremote as interface to send commands.

So the first option is that we make something like and we can control the arduino with openremote. Is this a good option does it work??

The other option is that we make a gateway with the Arduino Ethernet. Is this possible? Are there already project like this??

Posted by hapmore at Mar 11, 2013 10:14

If I understand correct, you don't have a KNX installation which means there is nothing where arduino can connect to.
The URL you gave is a system where arduino is physically connected to a KNX bus which is not the case in your scenario.

I can only see the solution where you use arduino as a gateway.

This means on arduino you need a process which receives commands via ethernet and controls your devices.
This is possible but depends on your arduino software and is not really related to OpenRemote.

Posted by mredeker at Mar 11, 2013 10:20

Yes indeed, maybe it is a easy way to use TCP or HTTP to talk to the arduino. But if we can make it talk to KNX we have a DIY solution for people that have KNX devices. So we make the arduino like a gateway but cheaper. if this isn't possible we buy a gateway and make the physical connection so in the future we can add KNX devices and keep the old installation like it is.
Are there projects on arduino that receive the commands from openremote?

Posted by hapmore at Mar 11, 2013 10:36

Search our forums for arduino. I think something was posted already.
I don't recall any details at the moment.

Posted by mredeker at Mar 11, 2013 10:59

Hi Marcus

adding to the KNX arduino question.
Looking through some OR threads, lots of people want to connect an arduino to OR. It looks to me that if we have an implementation on arduino for KNXnet/IP that would be great for a lot of people. Hence to choice to use KNX as the protocol. The knx info is spread out but google helps a lot. I have a couple of questions:

Is it necessary to implement the ACK in KNX to use it with OR? In other words: can you just set-up OR to use a certain IP address an port for KNX communication and listen (on de arduino) to incoming UDP connections without sending back an ACK (from the arduino)? Can you simple sent a KNX message (containing the info from the arduino) to the OR controller which updates the states? Without opening a connection first or managing ACK messages.

Posted by pspl at May 22, 2013 18:55

Why would you want to implement the rather complex KNX IP stack on Arduino to control something else?
The KNX protocol was designed 30 years ago to send data between hardware devices connected to 2 wires.
Just define yourself a UDP based protocol to speak to Arduino with that.

Posted by mredeker at May 22, 2013 22:01

Hi Marcus

thanks for the reply. I agree that creating a custom UDP would be faster for a one off project. I want to create something reusable for different systems (OR, misterhouse, openhab, ...) Although it is old KNX seems to be a dominating protocol. Therefore I would like my system to be KNX compatible. Figuring out the message is fine (info is scattered but google helps The info I'm missing is on the ACK part.

Posted by pspl at May 23, 2013 07:10

I don't know the details about the KNX protocol, but I would assume that you need to implement the complete stack to be compatible.

Posted by mredeker at May 23, 2013 07:52
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