Buses, Protocols and Systems for Home and Building Automation

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choose from a very large portfolio of KNX devices (more than 7000) which are the most
suitable with a function, price and design for their project. Product lines include not only
actors, sensors or visualization panels, but also gateways, which are capable to interconnect
the KNX system with all other building automation systems (e.g. BACnet, LON, EnOcean,
DALI, OpenTherm).
The system can be used for automation of every type and size of a building – from family
houses to office complexes and airports. A classical and basic application of the protocol is a
sophisticated light control, but today it covers all main tasks in building automation: energy
management; energy consumption measure; HVAC control (using KNX meteo-station);
advanced shutter and jalousie control; control of electronic devices; security and safety
tasks…
Similarly to other typical complex standardized protocol KNX uses more than one physical
layer:
- Twisted pair wiring (inherited from the BatiBUS and EIB)
- Powerline networking 230V (inherited from the EIB and EHS)
- Wireless KNX-RF (carrier frequency 868.3 MHz)
- Infrared
- Ethernet (KNXnet/IP)
The most frequently used medium is a twisted pair (called TP1) with a speed of 9600 bit/s,
which enables an interconnection of basic sensors and actors (field level). TP1 is also used as
a power supply for sensors. Ethernet physical layer is used mainly for a connection of
“higher” devices (automation level) like gateways, touch-panels, computers or PLCs with the
rest of the system.
The communication itself is based on two types of addresses: individual and group address.
Every device in a KNX net has a unique individual address. This address is used only for
programming, configuration and monitoring of the device – not for transferring process
data. For this purpose, there are dedicated group addresses. This type of address is not
bundled with a device, but with a “shared” variable of a specified type (we can also call them
net-variables). This variable forms the connection between sensors and actors, because it
logically connects together a group of variables of the same type located in different devices.
More than one device can listen to one group address and react on changes, but only one
device can write data to the group address (1 producer and 1 or more consumers). So, for
example, when a push-button is pressed, then it sends a packet with some group address.
Then a light actor, which is listening to this group address on the bus, recognizes the change
of the variable and switches the light on. Important fact is that there is no packet sent
directly (a packet with destination address equals to the individual address of the device)
from the push-button to the actor.
The KNX system can be configured and parameterized very easily. For this purpose, there
exists a tool called Engineering Tool Software (ETS) which is manufacturer independent and
easy to learn. So the KNX system avoids typical problems of other standardized systems (e.g.
BACnet) where exists a special configuration tool for every manufacturer quite often (you
cannot use a tool from one producer for devices using the same protocol/bus from another
producer). The ETS tool is managed by the KNX association and the manufacturers only have
to add a plug-in into the ETS tool. This plug-in is designed for a detailed configuration of a
device and its functions. The ETS tool exists in several modifications based on skills of a user.
Of course, there are still some bugs in the ETS tool. If the possibilities of the
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