Issue
BACnet controller objects that have not been overridden are displayed on I/A Series R2 graphic screens in the purple color as if they were overridden.
Environment
I/A Series R2 (Niagara) Graphic screens displaying values representing physical BACnet controller inputs.
Cause
Purple BACnet values (I/A Series R2 graphic override color) are internal BACnet points that can not be modified (display only).
This behavior is normal and began to appear in MNB controller firmware versions 1.2 and higher. Per the BACnet specification, read-only type points must be set to indicate an override condition. The root cause is a design change required by the BACnet specification to bring the controllers into compliance for BTL certification. The ASHRAE BACnet Specification 135-2004 specifies that the "read-only" type objects (e.g. Analog Value, Binary Value, etc.) OVERRIDDEN flag is:
Logical TRUE (1) if the point has been overridden by some mechanism local to the BACnet device. In this context "overridden" is taken to mean that the Present Value property is not changeable through BACnet services.
In this case, the override is meant to indicate to Niagara that the point is locally overridden (by the controller) and cannot be changed by the Niagara BACnet service (or user).
Resolution
There are several approaches that can be used to display these objects without the background showing the purple color.
One approach is to use a native Niagara AI object to buffer the value where the override condition is not transferred. In addition, if the BACnet points and Analog Input objects reside in a poll-on-demand container, the BACnet points will not be polled unless a gx type object is added and directly attached to the BACnet point. The graphic page will have a gx type object linked to the Analog Input object (displaying the value without the override) and another gx type object (invisible) linked to the BACnet point to start the point polling.
A second approach is to configure the GxText object so that the object property "statusColorEnabled" is false.
