BACnet Object Addressing

Hello,

I'm trying to understand how BACnet objects, specifically in my case Analog Inputs are addressed by consuming applications.

BACnet4J has a helper function which creates a new object id based on the type of object and the next available id. Ok, so let's say I have a analog input that I want to expose through BACnet4J. Each time my application is run, does that same analog input instance need to map to the same BACnet object id? Or do BACnet monitor applications form dependencies on other object properties?

To boil it all down, what information needs to remain immutable when my application is invoked to map the same analog input to a BACnet object so I behave like a traditional BACnet device to upstream consumers.

Regards,
Fred

Hi Fred,

That's a good question. I don't believe there are any specified requirements in this regard.

But when we look at the WhoHas service, there is a device id range (meaning your device id should be consistent), and there is a Choice object which can be either object identifier or name. So, theoretically either should do, but for maximum compatibility they should probably both remain the same for your object.

mlohbihler wrote:Hi Fred,

That's a good question. I don't believe there are any specified requirements in this regard.

But when we look at the WhoHas service, there is a device id range (meaning your device id should be consistent), and there is a Choice object which can be either object identifier or name. So, theoretically either should do, but for maximum compatibility they should probably both remain the same for your object.

I guess what I really need to do (if it's not cost prohibitive) is get a hold of some of the BACnet monitoring tools and see how folks monitor and administer BACnet devices. I would guess the configuration of a hard wire BACnet device rarely changes and one can form dependencies on the object ids. If I need to maintain the mapping between my analog sensors and an arbitrary object instance id, I can do that - I just don't know if it's necessary.

Regards,
Fred