BACnet/IP and BACnet MS/TP in a new air curtain controller, on embedded Linux

The challenge

Air curtains go into entrances of every kind of building, and those buildings do not agree on wiring. Some put every device on the IP network; others run an RS-485 MS/TP trunk to the doors. A controller that offers only one of the two loses the other half of the jobs.

For a new controller, the manufacturer wanted both data links from one BACnet implementation, so the objects, the behaviour and the testing are the same whichever way a site is wired.

Why the CAS BACnet Stack

• BACnet/IP and BACnet MS/TP come from the same library and the same interface. A build enables the data links it needs, and the product supplies a UDP socket for one and a serial port for the other.
• The stack builds for embedded Linux on x86, ARMv7 and ARM64 from its CMake presets.
• The source code is included and royalty-free, with direct support from the engineers who maintain the stack.

The solution

The CAS BACnet Stack runs in the controller’s Linux application as a BACnet server on BACnet/IP and BACnet MS/TP. The building management platform reads temperatures and the air curtain’s state, and drives activation from temperature.

Because both data links share one stack, the controller presents the same BACnet device and objects on either network.

Results

• Building management platforms activate the air curtain on temperature and monitor it.
• One controller fits buildings wired for BACnet/IP and buildings wired for BACnet MS/TP.