KNX BAOS Module 820
Serial interface and ObjectServer for EIB/KNX bus
KNX BAOS Module 820 serves as an interface to KNX/EIB both at the telegram and data point levels (KNX Application Layer). BAOS stands for ”Bus Access and ObjectServer”.
The module has the same function as the KNX Serial BAOS 870 but is designed for integration in a device (e.g. sensor or actuator).
Functionality of the ObjectServer
Connectivity to the KNX bus is increasingly becoming a critical feature in devices used in building automation. Full integration of the application with the KNX stack is certainly the best technical solution. However, this requires a comparatively high investment and is not economical in small numbers.
A more cost-effective method of connecting devices to KNX is offered by the KNX Serial BAOS 820 module. In addition to the KNX transceiver, it contains a microcontroller with a certified KNX stack. It also electrically isolates the device from the bus. Communication with the module takes place via the FT1.2 serial protocol. This protocol was introduced in KNX with the PEI (Physical External Interface) of the BCU2 (Bus Coupling Unit). It enables the transmission and reception of KNX telegrams in the EMI (External Message Interface) format.
For certain devices, however, it is preferable to not access the bus (TP) directly. If a telegram interface were used for these solutions, the devices would be able to access the KNX network, but would still have to generate and interpret KNX telegrams. Moreover, they would need to know the group address used in the KNX network.
It is far simpler for the KNX interface to take over this task. In this case, the KNX communication software in the module manages the data points, enabling the module to assign the received telegrams to the corresponding communication objects. The module can also independently generate and send group telegrams. The module offers 250 data points. A general ETS database (Engineering Tool Software) is available for setting the data types and linking the communication objects. Of course, it is also possible to create individual databases for your devices.
Each communication object has its own memory. The data point values are automatically updated upon reception. This temporally decouples bus communication from the application.
For accessing data point levels, additional services are introduced into the FT1.2 frame. The BAOS protocol is available at the end of this page. We also offer a test program that shows communication with the module.
A device (e.g. a sensor or actuator) is able to access the data points via FT1.2 without needing to know the KNX telegram syntax. A device addresses a data point via its number. If group addresses are later changed in the KNX network, the module can be readily updated with an ETS download. The device does not need to be reconfigured.
A development kit is available for the module:
- 1 development board
- 2 KNX BAOS 820 modules
- 1 USB cable A/B (micro)
Mechanical data module
- Dimensions (L x W): 44 x 25 mm, 1.5 mm board
- Installation: The PCB must be installed in a suitable housing prior to being started up.
- External supply for galvanically isolated UART 3.3 or 5 V DC
- Bus current consumption: 9 mA
- KNX Bus +/-
- Lern key
- Lern LED
- Power supply GND/VCC
- UART TX/RX