ETS6 (Engineering Tool Software, version 6) is the single software tool used by all KNX integrators worldwide for programming KNX installations. It is the only way to configure a KNX device: download applications, set parameters, and assign group addresses. Understanding ETS6 correctly — rather than learning it by trial and error — dramatically reduces commissioning time and prevents the address-structure mistakes that cause integration problems months after handover.

The ETS6 project structure

An ETS6 project has two parallel hierarchies that must both be configured. The building structure (topology view) organises by physical location: Area → Line → Device. This matches the physical KNX bus topology. The function structure (group addresses view) organises by function: lighting, blinds, HVAC, etc. A device in the topology view has communication objects — these are the "ports" through which data flows. Communication objects are linked to group addresses. The group address is the shared "channel" on which multiple devices communicate.

Individual addresses and the topology view

Every KNX device must have a unique individual address in the format Area.Line.Device. Area = 1-15, Line = 1-15 per area, Device = 1-255 per line. First device on any line should be the line coupler at 1.1.255 (or area coupler at 1.0.255 if at area level). Normal devices number from 1.1.1 to 1.1.64. Important rule: a KNX line (segment) supports maximum 64 devices, not 255 — even though the address space allows 255. Maximum 64 because the bus power supply supports 64 × 18mA ≈ 1152mA, and the collision detection protocol degrades above 64 devices.

In ETS6 topology view: right-click on Area 1 → Add Line → assign coupler. Right-click on Line → Add Device → select from catalogue. Assign individual address. The individual address is programmed to the device using the learn button (press button on device → ETS6 downloads address). This physical programming step is separate from the application/parameter download.

Group addresses: the link between devices

Group addresses are how devices talk to each other. When a KNX pushbutton is pressed, it sends a telegram to a group address. All devices that are "linked" to that group address (subscribed via the send/receive flag) respond. Standard 3-level group address format: Main/Middle/Sub. Create group addresses in ETS6 group view: right-click → Add main group → name it (e.g., "1 - Lighting"). Right-click on main group → Add middle group (e.g., "1/0 - Living Room"). Right-click on middle group → Add group address (e.g., "1/0/1 - Ceiling Light On/Off").

Then link devices: navigate to device in topology view → click on communication object (e.g., "Switch" object on pushbutton, output channel 1) → drag to group address "1/0/1". Or right-click → Link to group address. Do the same for the switch actuator's "Switch" object (output channel 1). Both devices are now linked: pushbutton send → telegram on 1/0/1 → actuator receives → output switches.

Data Point Types (DPTs)

Every group address and communication object has a DPT — the data type that defines the telegram format. Critical: both the sending and receiving device must use the same DPT on the same group address. Mismatched DPTs are the most common silent failure in KNX programming — the telegram is sent correctly but the receiving device ignores it. Common DPTs: DPT 1.001 (1-bit, switch: 0=off, 1=on), DPT 5.001 (1-byte, percentage 0-100%), DPT 9.001 (2-byte float, temperature °C), DPT 18.001 (1-byte, scene number + activate/learn), DPT 20.102 (1-byte, HVAC mode 0-4). ETS6 displays the DPT for each communication object — verify that linked devices show the same DPT.

Parameter pages

After assigning a device to the topology and linking group addresses, configure device parameters. Parameters control device behaviour: dimmable or switched operation, travel time for shutters, hold time for presence detectors, scene values, input type (NO/NC contact), cyclic sending interval. Navigate to device → Properties → Parameters. Work through each parameter page systematically. Key parameters for common devices: MDT Switch Actuator — channel type (switching/dimming/shutter), current limit, safety priority enable. MDT Dimmer — minimum brightness (%), maximum brightness (%), fade time (seconds). MDT Blind Actuator — travel time up (seconds), travel time down (seconds), slat travel time (seconds), automatic stop on limit position.

After configuring parameters, download to device: right-click device → Download → Application. The download writes the application firmware, parameters and filter table simultaneously. If you change parameters after the initial download, download again — parameters are not applied until downloaded.

The filter table: often forgotten

The filter table controls which telegrams pass through KNX line couplers and area couplers. If a telegram from Line 1 needs to reach a device on Line 2, the line coupler between them must have the group address in its filter table. ETS6 builds the filter table automatically based on the group address links in the project. However, the filter table must be downloaded to the coupler separately from the device application. Common error: adding a new group address link after the initial commissioning and forgetting to re-download the coupler filter table. Result: telegram sent from pushbutton never reaches the actuator on the other line, and no error appears anywhere in the system.

ETS6 group monitor for verification

After programming, use ETS6 Group Monitor (Project → Group Monitor or keyboard shortcut) to verify telegrams in real time. For each group address, you can see: value, last send time, last receive time, DPT. When you press a KNX pushbutton: you should immediately see the group address value change in group monitor. If you see the value change but the actuator doesn't respond: check the group address link on the actuator's communication object. If you don't see the value change: check the pushbutton group address link, check the coupler filter table, check the bus voltage.

Backup discipline

Before any ETS6 programming session, export the project (.knxproj file) to a dated backup location. After commissioning, export the final project with all group addresses and parameters. Provide a copy to the client and record the backup location in the O&M manual. ETS6 projects are the irreplaceable record of the installation — if the project file is lost, re-programming requires visiting every device individually, which can take days for a large installation.