KNX protocol interoperability for building automation on ultra-low-power MCUs

In buildings of varying sizes and complexity, automation systems are becoming more common and more important. Convenience, safety and energy efficiency are key factors driving smart surveillance and control of residential and building products. From lighting to window blinds control, to complex heating, ventilation and air conditioning (HVAC) components, and metering/management systems, residential and commercial buildings are equipped with smarter automation solutions. Every year, this trend is driving manufacturers around the world to release thousands of products in this market.

A typical building automation system consists of three components: a sensor, a communication channel, and an actuator.

Interoperability between building automation systems and KNX software on ultra-low-power MCUs

A set of sensors collects and processes data in the environment, from which a message is transmitted through a communication channel to different parts of the network that are operated by the actuator.

Take the safety system consisting of smoke detectors, intrusion sensors and alarms as an example. As soon as smoke is detected or someone illegally breaks into the home, the siren receives a message and makes a loud noise. The most basic requirement is that the siren can "understand" the smoke and intrusion detectors. As you can imagine, what happens if the smoke detector produced by manufacturer A uses communication protocol A and the communication protocol B used by manufacturer B's intrusion detector? How can the alarms understand the messages from these two detectors? In addition, if there are hundreds of vendors and they are using proprietary communication protocols, what should we do? Obviously, there must be a common "language" between all automation components to achieve their interoperability. And this is where KNX software works. The KNX communication protocol enables interoperability of building automation devices without regard to vendors, product lines, or even core functions. With KNX, communication between all interconnected devices is possible. For example, a light switch can communicate not only with the light bulb but also with smoke detectors, window shutter controls, and any other networked device.

In this type of communication, data security and reliability are critical. The MSP430FR5969 microcontroller (MCU) with non-volatile FRAM technology embedded on the chip enables the following functions:

The playback (playback) attack is prevented by using a non-volatile sequence counter that is incremented upon receipt of each data frame.

Secure storage of the Factory Device Set Key (FDSK) and all security keys that are established during configuration using the Memory Protection Unit (PMU).

Encryption of KNX network traffic with hardware AES accelerators.

Fast writes to non-volatile memory after receiving each data frame reduce the risk of message loss.

A low-energy storage of critical data when power is lost is detected, preserving the current state of the device.

Take the example of a thermostat that has a huge impact on FRAM technology. Even the most basic thermostats on the market allow users to create different temperature system configurations for energy savings. By continuously recording user settings and the most recent system state in non-volatile memory, the MSP430TM microcontroller supporting embedded FRAM technology can effectively resume normal operation after a power outage to achieve a low-power system and guarantee The comfort of the user's environment.

To learn more about this thermostat example, download our new TI Designs reference design: Wired KNX Thermostat Reference Design.

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