#943 Regarding Point Function and BACnet Mapping

Hareesh Reddy G.M Fri 3 Sep


This is regaring mapping of BACnet objects with Haystack point and where Haystack function to be considered. As per Haystack standard we have three point functions

sensor: input AI/BI sensor cmd: output, AO/BO, actuator, command sp: set point, schedule, etc.,

If we consider AWS profile of BACnet, we have around 60 Objects and if we want to map all these objects with Haystack point, do we have only these three point functions?

For example consider BACnet object "EventEnrollment" or "NotificatioClass", for these objects should we consider sp as point function?

Joel Bender Fri 3 Sep

BACnet has a very different model, there are only a few BACnet objects which easily fit into a Haystack model and those are the ones with a Present_Value property. There are others like a File Object that I would not expect to appear anywhere in a Haystack model. Some things like an Analog Value Object are not so clear if they are inputs or outputs.

The most specific reference to an atomic piece of data in BACnet is a BACnetDeviceObjectPropertyReference which includes a device identifier, object identifier, property identifier and optionally an array index. You would use a few of these to peek into something like an Averaging Object (which doesn't have a Present_Value) to reference the information you want from the properties it has.

Joel Bender Fri 3 Sep

I failed to mention that if you want to have enough content in your Haystack model to reflect changes to BACnet devices via Write Property or Write Property Multiple services you will also need an optional priority parameter (unsigned integer in the range 1..16) used when the property is commandable.

If you are looking to have a standard way of having everything about a BACnet object encoded as JSON (maybe with an "escape hatch" tag saying "this is BACnet and don't bother to validate it here") then that's already in ANNEX Z - JSON DATA FORMATS (NORMATIVE).

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