KNX Application Program

A switching actuator may have eight channels, but whether these become eight simple switching outputs or eight outputs with staircase lighting, scenes, lock function and status feedback is not decided by the hardware but by the application program. It brings along the list of communication objects and the parameter pages that appear in the ETS.

The hardware sets the limit, the program exploits it. A relay that measures no current will not gain energy metering from even the best application program. This is why many manufacturers offer several programs for the same hardware, a simple one and an extensive one, and the choice belongs in the planning.

The manufacturer supplies its application program as a product database, downloaded from their site and imported into the ETS. Since ETS4 the format is called `.knxprod` and is XML. Older files carry `.vd1` to `.vd5` and are containers holding the same thing; the ETS can convert them.

Only after the import does the device appear in the product catalogue and can be dragged into a project. Without a matching product database there is no device, even if it has long been physically on the wall.

For the project file the direction runs only one way: a project can be imported into the same or a newer ETS version, never into an older one. Anyone taking over an installation therefore first checks which version it was built with.

The ETS does not load one file but several things in sequence: the individual address, the application program itself, the configured parameters and the assignment of group addresses to communication objects.

This is why programming a device for the first time takes longer than any later run. On the second occasion the ETS transfers only what has changed, as long as the application program has stayed the same.

When a manufacturer releases a new version of its application program, that is not always a mere update. If the structure of the communication objects or parameters changes, the ETS treats it as a different program, and the device settings are gone afterwards.

The effort does not hit one device but all of the same type in the project. With twelve identical actuators that is an afternoon of work nobody planned for.

The rule that follows is inconvenient, but it saves those afternoons: **a running installation does not get a new application program just because one exists.** A change happens when a function is needed that did not exist before, or when a fault affecting the installation has been fixed. Before that, the project gets backed up.