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KNX is an
open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a common prerequisite that open standards use an open license that provides for extensibility. Typically, anybody can participate in their development due to ...
(see EN 50090,
ISO/IEC ISO/IEC JTC 1, entitled "Information technology", is a joint technical committee (JTC) of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Its purpose is to develop, maintain and ...
14543) for commercial and residential
building automation Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, HVAC (heating, ventilation and air conditioning), electrical, light ...
. KNX devices can manage lighting, blinds and shutters,
HVAC Heating, ventilation, and air conditioning (HVAC ) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. ...
, security systems, energy management, audio video, domestic appliances, displays, remote control, etc. KNX evolved from three earlier standards; the European Home Systems Protocol (EHS), BatiBUS, and the
European Installation Bus Instabus, is a decentralized open system to manage and control electrical devices within a facility. It is developed by Berker, Gira, Jung, Merten and Siemens AG. There are about 200 companies of electrical supplies using this communication protoco ...
(EIB or Instabus). It can use
twisted pair Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced ...
(in a
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...
, line or
star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
topology Topology (from the Greek language, Greek words , and ) is the branch of mathematics concerned with the properties of a Mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformat ...
), powerline, RF, or IP links. On this network, the devices form distributed applications and tight interaction is possible. This is implemented via interworking models with standardised datapoint types and
objects Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an ai ...
, modelling
logical Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure of arg ...
device channels.


Standard

The KNX standard has been built on the OSI-based EIB communication stack extended with the
physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechani ...
s, configuration modes and application experience of BatiBUS and EHS. KNX installations can use several physical communication media: *
Twisted pair Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced ...
wiring (TP1 Cable) (inherited from the EIB standard). (The previously inherited BatiBUS communication medium (TP0) is no longer part of the KNX Specifications.) * Power-line networking (inherited from EIB standard). (The previously inherited EHS communication medium (PL132) is no longer part of the KNX Specifications.) *
Radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
(KNX-RF) * IP (also referred to as EIBnet/IP or KNXnet/IP) KNX is not based on a specific hardware platform and a network can be controlled by anything from an 8-bit
microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...
to a PC, according to the demands of a particular building. The most common form of installation is over twisted pair medium. KNX is an approved standard by the following organisations, ( inter alia): * International standard (ISO/IEC 14543-3) * European standard (
CENELEC CENELEC (; ) is responsible for European standardization in the area of electrical engineering. Together with ETSI (telecommunications) and CEN (other technical areas), it forms the European system for technical standardization. Standards harmon ...
EN 50090 and CEN EN 13321–1) *US standard (
ANSI The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...
/
ASHRAE The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE ) is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration (HVAC&R) systems design and constructio ...
135) * China
Guobiao The National Standards of the People's Republic of China (), coded as , are the standards issued by the Standardization Administration of China under the authorization of Article 10 of the Standardization Law of the People's Republic of China. ...
(GB/T 20965) It is administered by the KNX Association cvba, a non-profit organisation governed by Belgian law which was formed in 1999. The KNX Association had 500 registered hardware and software vendor members from 45 nations as at 1 July 2021. It had partnership agreements with 100,000 installer companies in 172 countries and more than 500 registered training centres. This is a royalty-free
open standard An open standard is a standard that is openly accessible and usable by anyone. It is also a common prerequisite that open standards use an open license that provides for extensibility. Typically, anybody can participate in their development due to ...
and thus access to the KNX specifications is unrestricted.


Architecture

KNX devices are commonly connected by a twisted pair bus and can be modified from a controller. The bus is routed in parallel to the electrical power supply to all devices and systems on the network linking:All information in this and subsequent sections is summarised from *
Sensors A sensor is often defined as a device that receives and responds to a signal or stimulus. The stimulus is the quantity, property, or condition that is sensed and converted into electrical signal. In the broadest definition, a sensor is a devi ...
(e.g. push buttons, thermostats, anemometers, movement) gather information and send it on the bus as a data telegram; *
Actuators An actuator is a component of a machine that produces force, torque, or displacement, when an electrical, pneumatic or hydraulic input is supplied to it in a system (called an actuating system). The effect is usually produced in a controlled way. ...
(dimming units, heating valves, displays) receive data telegrams which are then converted into actions; and *Controllers and other logic functions (room temperature controllers, shutter controllers and other) * System devices and components (e.g. line couplers, backbone couplers). Classifying devices as either "sensor" or "actuator" is outdated and simplistic. Many actuators include controller functionality, but also sensor functionality (for instance measuring operating hours, number of switch cycles, current, electrical power consumption, and more). Application software, together with system topology and commissioning software, is loaded onto the devices via a system interface component. Installed systems can be accessed via LAN, point to point links, or phone networks for central or distributed control of the system via computers, tablets and touch screens, and smartphones. The key features of the KNX architecture are: * Interworking and distributed application models for the building automation various tasks; * Schemes for configuration and management of resources on the network, and to permit the binding of parts of a distributed application in different nodes; * A communication system with a message protocol and models for the communication stack in each node (capable of hosting distributed applications (KNX Common Kernel); and *Models for the realization of these elements when developing actual devices to be mounted and linked in an installation.


Applications, interworking and binding

Central to the KNX architecture concepts are datapoints (inputs, outputs, parameters, and diagnostic data) which represent process and control variables in the system. The standardised containers for these datapoints are group objects and interface object properties. The communication system offers a reduced instruction set to read and write datapoint values. Datapoints have to conform to standardised datapoint types, themselves grouped into functional blocks. These functional blocks and datapoint types are related to applications fields, but some of them are of general use (such as date and time). Datapoints may be accessed through unicast or multicast mechanisms. To logically link applications' datapoints across the network, KNX has three underlying binding schemes: one for free, one for structured and one for tagged binding: * In ''free binding,'' links between datapoints are not prescribed - in combination with free addressing, this supports customized multicast grouping at the level of individual datapoints and is central to S-mode configuration (see below); * In ''structured binding,'' the KNX specification stipulates a precise pattern for linking a whole set of datapoints, usually corresponding to a Functional Block or Channel (push-button modes follow this concept); * ''Tagged binding'' is also pre-structured by the application models, but the numerical value of address is part of its value.


Kernel and message protocol

The common kernel sits on top of the physical layers and the medium-specific data link layer and is shared by all the devices on the KNX Network. It is OSI 7-layer model compliant: * A general data link layer, which sits above the specific data link layers for each medium, provides access control and the logical link control; * A network layer (for nodes with routing functionality) provides a segment-wise acknowledged telegram (
frame A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (con ...
) and controls the
hop count In wired computer networking a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices thro ...
of a frame; * A transport layer enables four types of communication: one-to-many connectionless (multicast), one-to-all connectionless (broadcast), one-to-one connectionless, one-to-one connection-oriented; * (OSI session and presentation layers are empty); and * An application layer offers a toolkit of services to the application process.


Configuration modes

An installation has to be configured at the network topology level and at individual nodes or devices. The first level is a precondition or “bootstrap” phase, prior to the configuration of the distributed applications, i.e. binding and parameter setting. Configuration may be achieved through a combination of local activity on the devices (such pushing a button), and active network management communication over the bus (peer-to-peer, or more centralized master-slave). The KNX configuration mode: * picks out a certain scheme for configuration and binding; * maps it to a particular choice of address scheme; and * completes all this with a choice of management procedures and matching resource realizations. Some modes require more active management over the bus, whereas some others are mainly oriented towards local configuration. There are three categories of KNX devices: *A-mode or "Automatic mode" devices which can configure themselves, and are able to be installed by the end user; *E-mode or "Easy mode" devices that require basic training to install: their behaviour is pre-programmed, but configuration parameters need to be tailored to the user's requirements; or *S-mode or "System mode" devices that can be used to create sophisticated
building automation Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, HVAC (heating, ventilation and air conditioning), electrical, light ...
systems: they have no default behaviour, and must be programmed and installed by specialists. KNX encompasses tools for project engineering tasks such as linking a series of individual devices into a functioning installation and integrating different media and configuration modes. This is embodied in an ''Engineering Tool Software'' (ETS) suite.


Devices

A KNX installation always consists of a set of devices connected to the bus or network. Device models vary according to node roles, capabilities, management features and configuration modes, and are all laid down in the profiles. There are also general-purpose device models, such as for bus coupling units (BCUs) or bus interface modules (BIMs). Devices may be identified and subsequently accessed throughout the network either by their individual address, or by their unique serial number, depending on the configuration mode. (Unique serial numbers are allocated by the KNX Association Certification Department.) Devices can also disclose both a manufacturer specific reference and functional (manufacturer independent) information when queried.


Topology and addressing

A KNX wired network can be formed with
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...
, line and
star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
topologies, which can be mixed as needed;
ring (The) Ring(s) may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell Arts, entertainment, and media Film and TV * ''The Ring'' (franchise), a ...
topologies are ''not'' supported. A tree topology is recommended for a large installation. KNX can link up to 57,375 devices using
16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...
addresses. * The lowest eight bits provide up to 256 addresses within one line, which can consist of up to four segments, each having a maximum of 64 (TP1-64) devices, or up to 256 (TP1-256) devices. Each segment requires a local power supply and the maximum length of a segment is 1000 m. (The actual number of devices supported is dependent on the power supply and the power load of the individual devices.) Segments connected with line
repeater In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some ...
s can extend to a length of 4000 m and link up to 256 devices. * Lines may be grouped together into an area, with up to 15 lines connected to a main line via line couplers. The next four bits of the address are used to identify individual lines. * An entire domain can be formed with 15 areas linked by a backbone line using backbone couplers, and the top four bits of the address space identify an area. (Line repeaters may not be used on a backbone or mainline.) Coupling units allow address filtering which helps to improve performance given the limited bus signal speed. An installation based on KNXnet/IP allows the integration of KNX sub networks via IP as the KNX address structure is similar to an IP address.


Physical layer


TP 1

The TP1
twisted pair Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced ...
bus (inherited from EIB) provides
asynchronous Asynchrony is any dynamic far from synchronization. If and as parts of an asynchronous system become more synchronized, those parts or even the whole system can be said to be in sync. Asynchrony or asynchronous may refer to: Electronics and com ...
, character oriented data transfer and
half-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...
bidirectional
differential signaling Differential signalling is a method for electrically transmitting information using two complementary signals. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conduc ...
with a signaling speed of 9600 bit/s.
Media access control In IEEE 802 LAN/MAN standards, the medium access control (MAC), also called media access control, is the layer that controls the hardware responsible for interaction with the wired (electrical or optical) or wireless transmission medium. Th ...
is via
CSMA/CA Carrier-sense multiple access with collision avoidance (CSMA/CA) in computer networking, is a link layer multiple access method in which carrier sensing is used. Under CSMA/CA, nodes attempt to avoid collisions by beginning transmission only af ...
. Every bus user has equal data transmission rights and data is exchanged directly (peer-to-peer) between bus users.
SELV Extra-low voltage (ELV) is an electricity supply voltage and is a part of the low-voltage bandIEC 61140:2016 Chapter 4.2 in a range which carries a low risk of dangerous electrical shock. There are various standards that define extra-low voltage. ...
power is distributed via the same pair for low-power devices. A deprecated specification, TP0, running at a slower signalling speed of , has been retained from the BatiBUS standard but KNX products cannot exchange information with BatiBUS devices.


PL 110

PL 110 power-line transmission is delivered using spread frequency shift keying signalling with asynchronous transmission of data packets and half duplex bi-directional communication. It uses the central frequency 110 kHz (CENELEC B-band) and has a data rate of 1200 bit/s. It also uses CSMA. KNX Powerline is aimed at smart
white goods A major appliance is a non-portable or semi-portable machine used for routine housekeeping tasks such as cooking, washing laundry, or food preservation. Such appliances are sometimes collectively known as white goods, as the products were tradi ...
, but the take-up has been low. An alternative variant, PL 132, has a carrier frequency centred on 132.5 kHz (CENELEC C-band).


RF

RF enables communication in the 868.3 MHz band for using
frequency shift keying Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is encoded on a carrier signal by periodically shifting the frequency of the carrier between several discrete frequencies. The technology is used for c ...
with Manchester data encoding.


IP

KNXnet/IP port 3671 has integration solutions for IP-enabled media like
Ethernet Ethernet ( ) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
(IEEE 802.2),
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is li ...
, WiFi/Wireless LAN (IEEE 802.11),
FireWire IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony a ...
(IEEE 1394) etc.


Frame format

Ignoring any preamble for medium-specific access and collision control, a frame format is generally:


Security

KNX Telegrams can be signed or encrypted thanks to the extension of the protocol that was developed starting in 2013, KNX Data Secure for securing telegrams on the traditional KNX media TP and RF and KNX IP Secure for securing KNX telegrams tunnelled via IP. KNX Data Secure became an EN standard (EN 50090-3-4) in 2018, KNX IP Secure an ISO standard (ISO 22510) in 2019.


Conformity

Any product labeled with the KNX trademark must be certified to conform with the standards (and thus interoperable with other devices) by accredited third party test labs. All products bearing the KNX logo are programmed through a common interface using the vendor-independent ETS software.


See also

* DOLLx8 * EnOcean *
Home automation Home automation or domotics is building automation for a home. A home automation system will monitor and/or control home attributes such as lighting, climate, entertainment systems, and appliances. It may also include home security such ...
* INSTEON *
Z-Wave Z-Wave is a wireless communications protocol used primarily for residential and commercial building automation. It is a mesh network using low-energy radio waves to communicate from device to device, allowing for wireless control of smart home d ...
*
Intelligent building Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC (heating, ventilation and air conditioning), electrical, lighting, ...
*
Lighting control console A lighting control console (also called a lightboard, lighting board, or lighting desk) is an electronic device used in theatrical lighting designer, lighting design to control multiple stage lighting, stage lights at once. They are used throughou ...
*
Lighting control system A lighting control system is intelligent network-based lighting control that incorporates communication between various system inputs and outputs related to lighting control with the use of one or more central computing devices. Lighting control ...
*
OpenTherm OpenTherm (OT) is a standard communications protocol used in central heating systems for the communication between central heating appliances and thermostatic controllers. As a standard, OpenTherm is independent of any single manufacturer. A contr ...
* Smart environment *
Touch panel A touchscreen (or touch screen) is a type of display that can detect touch input from a user. It consists of both an input device (a touch panel) and an output device (a visual display). The touch panel is typically layered on the top of the e ...
* UPB *
Matter (standard) Matter is a technical standard for smart home and IoT (Internet of Things) devices. It aims to improve interoperability and compatibility between different manufacturers and security, and always allowing local control as an option. Matter orig ...
, a proprietary, royalty-free standard for integration of home automation equipment


References


External links

* {{Authority control Computer buses Building automation Home automation cs:EIBA sq:EIB sistemet