BACnet Protocol stacks from Cimetrics. Choose the one which better suites your development. The Cimetrics BACstac is the leading 3rd party BACnet protocol stack (SDK) with a customer list that includes many well-known brands in the HVAC, lighting control and physical access control industries world wide. Our first BACstac license was sold in 1996 , and we continue to update our BACstac products as the BACnet standard evolves.