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Introduction: Programming KNX Installations using ETS, Now and in the Future

By Vassilios Lourdas, KNX Association.

KNX is the leading global standard for home and building control and is complied with by numerous manufacturers. This means that you can mix and match products from different companies, and they will all work together. But what is the technology behind KNX, and what is the future of its only commissioning tool, ETS? The following short overview summarises some major points.

KNX system architecture

KNX is based on a bus technology. This means that all physical devices in a KNX system use the same transmission method and are able to exchange data via a common bus network. Access to the bus network is clearly regulated using the ‘bus access’ method.

All KNX devices are connected to a common bus, so they all see the same information. Most of the data transmitted are not payloads (e.g. light on/light off signals), but address information (i.e. where have the data come from? Where are they going to?)

An important feature of the KNX bus system is its decentralised structure. Every KNX device has its own microprocessor, which means that there is no need for a central control unit, because the ‘intelligence’ of the system is spread across all of its devices. Centralised units are possible, but these tend to be used for very specialised applications.

A major advantage of KNX’s decentralised structure is that, if one device fails, the others continue to function, since the configuration is done individually, at device level. Only those applications dependent on the failed device will be interrupted.

Generally, in a KNX system, devices fall into three categories: • Sensors. • Actuators. • System devices.

Sensors are devices that detect events or actions in the building. Sensors can include presence detectors, push buttons, touch panels, apps for mobile devices etc. Events or actions could include things such as someone pressing a button, someone moving, a temperature falling above or below a set value, etc. Sensors convert events into telegrams (data packets), and send them along the bus cable.

Examples of KNX sensors
Examples of KNX sensors

Actuators are devices that receive these telegrams and convert the commands embedded in them, into actions. They are basically switches and dimmers for lighting, shading, heating etc. Sensors issue commands, while actuators receive them.

System devices are products such as power supplies, programming interfaces, couplers, etc.

KNX Actuator
Examples of actuators

System devices are products such as power supplies, programming interfaces, couplers, etc.

KNX system device
The Power Supply from Ekinex is an example of a system device

Creating the KNX bus

KNX has been designed to be very flexible, so that it can be installed in all kinds of building and environment. If a new building is being created, it would be usual to create the KNX bus using a cable, but for retrofit in existing buildings, re-wiring is not always possible. KNX offers a number of ways to create the bus:

• KNX Twisted Pair (KNX TP) – communication via a twisted pair data cable (bus cable). • KNX Powerline (KNX PL) – uses the existing mains network. • KNX Radio Frequency (KNX RF) – wireless communication via radio signal. • KNX IP – communication via Ethernet.

KNX Twisted Pair (KNX TP) cable. Only one cable is required to create the bus.
KNX Twisted Pair (KNX TP) cable. Only one cable is required to create the bus.

Programming the KNX system

A KNX system can be programmed by one of the following two modes:

• S-Mode : the majority of KNX products today are designed to be configured and commissioned using S-Mode. To do this, a special software, namely ETS Professional, is required. This is Windows-based software that runs on a PC.

• E-Mode: products designed for E-mode are configured not using a PC, but a handheld unit, push buttons, or other means. This configuration method is suitable for electricians with a basic knowledge of bus technology, but no software skills. S-Mode devices can, however, always be added to an E-Mode installation at a later stage.