To set up group addresses in KNX ETS programming, you create logical address objects in the ETS software, assign them to device communication objects, and then download the configuration to your KNX installation. Group addresses are the backbone of any KNX project — they define which devices talk to each other and how. The sections below walk through every key question, from basic structure to real-world troubleshooting.
What are group addresses used for in KNX ETS?
Group addresses in KNX ETS are logical identifiers that link communication objects across different devices, allowing them to exchange data on the KNX bus. When a button is pressed or a sensor sends a value, the associated group address tells every subscribed device what to do with that signal. Without group addresses, KNX devices have no way to communicate with each other.
Think of a group address as a shared channel. A push button sends a telegram to a specific group address, and every actuator or device that is linked to that same address will respond. This makes KNX extremely flexible: you can link one switch to multiple lights, or one temperature sensor to multiple thermostats, simply by assigning them to the same group address.
Group addresses also carry data types, which define what kind of information is transmitted. A switching command uses a 1-bit data type, a dimming value uses a percentage-based type, and a temperature reading uses a 2-byte floating point value. Matching data types correctly across all linked objects is essential for the system to function as intended.
How are group addresses structured in ETS?
Group addresses in ETS follow a hierarchical structure with either two or three levels, expressed as numbers separated by slashes. The most common format is three-level addressing, written as Main/Middle/Sub (for example, 1/1/1). This gives installers a logical way to organise addresses by function, floor, or room across large projects.
In the three-level model, the main group typically represents a functional category such as lighting or heating. The middle group narrows it down to a zone or floor, and the sub group identifies the specific function or device within that zone. A well-planned group address structure makes the project far easier to maintain, expand, and hand over to other engineers.
ETS also supports a two-level structure (Main/Sub) and a free structure where addresses are entered as plain numbers. For most professional installations, the three-level structure is the preferred standard because it scales cleanly and remains readable as projects grow.
What is the difference between a sending and receiving group address?
In KNX ETS programming, a sending group address is the address assigned to a communication object that transmits telegrams onto the bus. A receiving group address is one assigned to an object that listens for incoming telegrams and acts on them. A single group address can have one sender and multiple receivers, but the roles are defined at the communication object level, not the address itself.
Every communication object in ETS has flags that determine its behaviour. The most important flags are:
- Transmit (T): the object sends a telegram when its value changes
- Write (W): the object accepts incoming write telegrams
- Read (R): the object responds to read requests from the bus
- Initialise (I): the object reads its value from the bus on startup
A button input typically has the Transmit flag active, while a light actuator has the Write flag active. Both are linked to the same group address. Understanding these flags is critical in KNX ETS programming because incorrect flag settings are one of the most common causes of devices not responding as expected.
How do you create and assign group addresses in ETS step by step?
Creating and assigning group addresses in ETS is a straightforward process once your devices are added to the project. You work within the Group Addresses panel to create the addresses, then link them to communication objects in the Building or Topology view.
Here is the typical workflow:
- Open your ETS project and navigate to the Group Addresses panel.
- Create a main group by right-clicking and selecting “Add Main Group.” Name it clearly, for example “Lighting.”
- Add a middle group under the main group, such as “Ground Floor.”
- Create a sub group within the middle group for the specific function, such as “Living Room On/Off.” ETS will assign the next available address automatically.
- Link the group address to a communication object by dragging it onto the relevant object in the device view, or by right-clicking the object and selecting the address from the list.
- Repeat for all functions in your project, then download the configuration to your devices.
A clean naming convention from the start saves significant time during commissioning and future modifications. Many experienced KNX installers define the full group address structure on paper or in a spreadsheet before opening ETS.
Why are some group addresses not working after programming?
Group addresses that do not work after KNX ETS programming are almost always caused by one of three issues: incorrect communication object flags, mismatched data types between sender and receiver, or the configuration not being properly downloaded to one or more devices.
Start troubleshooting by using the ETS Group Monitor. This tool displays live bus traffic and shows you which telegrams are actually being sent and received. If a telegram appears in the monitor but the actuator does not respond, the issue is likely a missing Write flag on the receiving object or a data type mismatch. If no telegram appears at all when you trigger the source device, the Transmit flag on the sending object may be inactive, or the device download was incomplete.
Another common cause is assigning the same group address to objects with incompatible data types. For example, linking a 1-bit switch object to a 1-byte value object will result in no visible response even though the telegram is transmitted correctly. Always verify that the data point type (DPT) matches across every object linked to a group address.
How do KNX group addresses connect to the xxter controller?
The xxter controller integrates directly with your KNX installation and reads the group addresses from your ETS project. Once the controller is connected to the KNX bus, it can send and receive telegrams on any group address, making it possible to control and monitor your entire installation through the xxter app on a smartphone, tablet, or computer.
You do not need to reprogram your ETS group addresses to work with xxter. The controller sits alongside your existing KNX infrastructure and communicates using the same group addresses already configured in ETS. You simply link the relevant group addresses to the functions you want to expose in the xxter interface, such as lights, blinds, thermostats, or scenes.
How xxter supports KNX professionals
xxter is built specifically for professional KNX installers who want to deliver a reliable, user-friendly end result without adding complexity to their programming workflow. The xxter controller works directly with your ETS group address structure, requiring no changes to your existing configuration. Here is what xxter brings to a professional KNX project:
- Direct KNX bus integration: the controller connects to your installation and communicates via group addresses without additional middleware
- Free app on unlimited devices: clients can use the xxter app on smartphones, tablets, and computers with no subscription fees or licence costs
- Voice control via Pairot: the Pairot bridge makes any KNX installation compatible with Apple HomeKit, Amazon Alexa, and Google Assistant
- Smart Energy Management: the xxter Smart Energy Manager monitors and optimises energy use based on weather data and dynamic pricing
Whether you are commissioning a residential project or a larger building installation, xxter gives your clients a polished, intuitive interface built on top of the professional KNX foundation you have already programmed. Explore the xxter controller and compatible KNX products and discover how it fits into your next KNX project at xxter.com. For questions about your specific installation, you can also get in touch with the xxter team。