With the growing concern of energy scarcity, efficient utilization of energy for energy saving in a smarter way has become a crucial element in smart building applications. KNX is an open standard for commercial and residential building automation. In this article, we will introduce the development of the KNX standard and its applications, along with the related solutions that support KNX technology.
A mature open standard for commercial and residential building automation is KNX
KNX is an open standard used for commercial and residential building automation. KNX devices can be used to control lighting, blinds and curtains, HVAC systems, security systems, energy management, audio/video, white goods, displays, and remote control, among others. By utilizing KNX, overall convenience and efficiency of smart building applications can be enhanced, leading to improved energy utilization.
The KNX standard has been in existence for several decades and is a mature technology. It evolved from three early standards including European Home Systems Protocol (EHS), BatiBUS, and European Installation Bus (EIB or Instabus). It can be implemented using twisted pair wiring (in tree, line, or star topology), powerline, radio frequency (RF), or IP links. In this network, devices form distributed applications and interact closely, facilitated by a common model with standardized data point types and objects, modeling logical device channels. The protocol has been widely used to enhance energy efficiency in homes and buildings.
One of the wide applications of KNX is room automation, where central control components not only facilitate operations such as lighting and shading but also integrate with available valves on heating or cooling elements for individual room control. For example, a KNX system can send notifications to close the HVAC when a window is opened to avoid energy waste.
KNX also enables the connection of various energy meters, allowing people to closely monitor data and identify sources of excessive energy consumption to implement energy control measures and prevent waste. In fact, some KNX products even allow submetering at the circuit level for more precise understanding of energy consumption.
Meanwhile, among manufacturers supporting the KNX standard, some offer battery storage devices whose usage status can be monitored through KNX. Manufacturers also utilize KNX to control the connection between homes and charging stations. Therefore, KNX solutions become a key element for solar inverters, energy storage, and battery management systems (BMS) manufacturers.
The KNX market is experiencing rapid growth, with major application categories including control and connectivity, lighting, energy management, home entertainment, smart appliances, and security. According to statistics, the smart home market in China is expected to reach nearly $37 billion by the end of 2025, and the global KNX product market is projected to reach around $50 billion by 2030, with a compound annual growth rate (CAGR) of approximately 15.9%.
Diverse KNX products enhance energy efficiency
There is currently a wide variety of KNX-related products available on the market. For example, KNX-compatible energy meters (electricity, gas, water, or heat meters) provide insights into energy consumption, allowing for better understanding of how to reduce energy costs and improve the energy efficiency of machinery and electrical assets. These KNX devices offer long-term data logging, and the data can be easily accessed using a KNX-IP Router and standard web browser for further analysis and remote diagnostics.
Furthermore, KNX gateways for solar panel inverters offer a simple solution for transmitting all relevant data from the inverter to the KNX system. This enables integrators to utilize fully integrated solar panel inverters for energy management, with the data used to optimize energy consumption, monitor trends, or trigger specific operations within the KNX system.
Additionally, KNX can be applied to battery storage units, allowing the storage of energy generated by photovoltaic systems. This enables the use of self-produced clean energy to fulfill approximately 75% of annual energy needs. As this energy is generated on-site, on the rooftop, rather than sourced from external energy providers, it allows for more independent management of energy consumption and a comprehensive understanding of energy utilization.
With electric vehicles becoming increasingly popular, KNX devices can manage home charging stations and provide precise monitoring of the energy consumption of electric vehicles when charging at external charging stations.
KNX has designed various functional blocks based on the EN50491-12-2 standard, facilitating data exchange between customer energy managers and energy consumers/producers in buildings. This enables better monitoring and processing of energy consumption data to avoid energy waste. KNX has a significant impact on energy consumption, especially in commercial and public buildings where the scale is larger, resulting in faster return on investment compared to residential buildings. However, even in residential applications, the return on investment becomes more significant as energy costs rise.
Compared to conventional installations of smart building systems, where each function requires one or more cables, and each device is dedicated to a single function, and if you need to change the functionality, you must modify the physical installation. KNX installations require only one cable (the bus) for transmitting all information. The functionality depends on the programming, and changes can be made without altering the physical installation. This means that a single device can have multiple uses, and a single network can accommodate over 65,000 devices with assigned addresses, providing more application advantages.
Micro KNX twisted pair transceiver with voltage regulators
STKNX is a transceiver designed for KNX TP (Twisted Pair) communication, introduced by ST. The device features a small package and requires minimal external components, making it ideal for compact KNX node designs. It offers a simple microcontroller interface, allowing for easy replacement of physical layers discrete component implementations.
The STKNX device integrates two voltage regulators for external applications. It includes an optional 3.3V/5V - 20mA linear regulator and an adjustable 1V to 12V - 150mA high-efficiency DC/DC step down switching converter. The device also integrates a KNX bus power extractor, supporting up to 30mA of bus current to power external components while meeting the power requirements of the STKNX transceiver. Additionally, the device adheres to KNX specifications regarding the limitation of bus current slew rates. STKNX ensures a secure coupling with the bus and provides bus monitoring alerts in case of bus power consumption issues.
The STKNX device is available in an ultra-thin and small-footprint 4x4mm VQFNPN24 package. It is KNX certified and supports the KNX TP1-256 standard. It can easily be connected to microcontrollers such as the STM32, offering a compact system solution with two integrated voltage regulators. The device does not require an external crystal and operates within a temperature range of -40°C to +85°C.
The STKNX device, combined with the STM32 microcontroller, can be paired with TAPKO or Shufan KAIStack KNX protocol stack software support. Through close collaboration between ST and TAPKO, the STKNX device has been jointly developed and certified by KNX, providing a complete solution for KNX twisted-pair applications.
A low-power, cost-optimized dual-radio KNX solution
ST has also introduced the KNX-RF dual-radio solution, which includes the S2-LP and BlueNRG-2 chips, enabling a dual-radio solution that supports both KNX-RF and BLE. This solution, combined with TAPKO's KNX-RF protocol stack software, provides a convenient wireless solution for KNX applications.
ST's S2-LP is a high-performance, ultra-low-power RF transceiver designed for RF wireless applications in sub-1GHz frequency bands. It operates in license-free ISM and SRD bands at 433, 512, 868, and 920 MHz, but can also be programmed to operate in additional frequency ranges such as 413-479 MHz, 452-527 MHz, 826 MHz-958 MHz, and 904-1055 MHz.
The S2-LP supports various modulation schemes, including 2(G)FSK, 4(G)FSK, OOK, and ASK, with programmable air data rates from 0.1 to 500 kbps. It can be used in systems with channel spacing down to 1 kHz and supports narrow band operation. The S2-LP has an RF link budget higher than 140 dB for long communication ranges and meets regulatory requirements for global regions, including Europe, Japan, China, and the United States.
ST also offers the BlueNRG-2, a Bluetooth Low Energy (BLE) single-chip solution that can be paired with the S2-LP. BlueNRG-2 is a SoC (System-on-Chip) with ultra-low-power BLE that complies with Bluetooth standard specifications. It extends the functionality of ST's existing BlueNRG series of Bluetooth network processors and features a built-in Cortex M0 core for running the user application code.
The BlueNRG-2 includes 256KB of programing Flash memory, 24K static RAM (divided into two banks of 12KB each) with retention capability, and standard peripheral communication interfaces such as SPI, UART, and I2C. Additionally, it is equipped with various modules such as a multi-functional timers, watchdog, real-time clock, and DMA controller.
The internal ADC module of the BlueNRG-2 can be connected to external analog sensors, and it can also read measurements from an internal battery voltage sensor. A built-in digital filter can be used to process external PDM (Pulse Density Modulation) data streams. The BlueNRG-2 offers excellent RF performance and features a high-efficiency DC-DC converter with ultra-low-power characteristics, which also improves power consumption in sleep modes, further extending the battery life in practical applications.
Through close collaboration with TAPKO, ST has combined the S2-LP, BlueNRG-2, and KAIStack KNX protocol stack software, achieving KNX certification. This dual-radio solution meets the requirements for low-power and cost-optimized applications.
ST provides a range of certified chipsets for KNX applications, including the STKNX and STM32 dual-twisted-pair chipsets mentioned earlier, as well as the S2-LP and BlueNRG-2 chipset for KNX RF combined with BLE. The S2-LP can also be paired with the STM32 to create a KNX RF chipset, which can be combined with protocol stack software from TAPKO, Nanjing Shufan, and MKFC to meet the wired and wireless KNX application needs.
Conclusion
KNX has a remarkable track record in energy efficiency, and recent technological advancements have allowed for its expansion into using KNX technology to enhance energy management purposes. KNX energy management is an active approach that aims to provide optimized energy usage based on user demand during any given time period, enabling the creation of more environmentally friendly environments. KNX plays a crucial role in smart building energy applications. The wired and wireless KNX solutions offered by ST, as described in this article, can meet the diverse needs of KNX applications and accelerate the development speed of customers' KNX products, seizing the abundant business opportunities in smart building energy applications.