BACnet/IP monitoring for ultra-low temperature freezers, on a TI AM335x Linux controller

The challenge

An ultra-low temperature freezer holds samples a lab or a hospital cannot replace. Facilities teams want its environment on the same screens as the rest of the building, with alarms that reach the people on call, not a separate panel that someone has to walk past.

In those buildings the facilities system speaks BACnet/IP. The freezer’s controller, an ARM processor running embedded Linux, needed to present its environment as BACnet objects the building system could discover and watch.

Why the CAS BACnet Stack

• The stack builds for ARM Linux from the same C/C++ source as every other target, with CMake presets for ARMv7 and ARM64, so it fits a TI AM335x controller without a port.
• Change-of-value subscriptions let the building system be told when a reading changes, instead of polling every freezer.
• The source code is included and royalty-free, and the engineers who maintain the stack support the integration directly.

The solution

The CAS BACnet Stack runs in the controller’s Linux application as a BACnet/IP server. The application keeps its own readings and the stack asks for them through callbacks when a client reads a property, so the measurement code does not change.

Each freezer appears on the building network as its own BACnet device, with its environment as objects the building system can read and subscribe to.

Results

• Research labs and hospitals monitor each freezer’s environment from their building automation system.
• Freezers report over BACnet/IP on the building’s existing network.