Starting in AX-3.5 (also builds 3.3.32 and later, and 3.4.54 and later), Lon proxy point support was added for values received from numeric and enumerated LonData elements with “invalid” or other specified values to be represented as “null” values, versus the “nan” (not a number) representation for invalid.

This can be useful if the point’s out slot is linked to the input of a math component (an Average object, for example), or to the priority array input of a writable control point. The null value causes the value to be ignored, instead of evaluated as invalid. In the linked Average example, its output reflects the average of the other “non-null” input values (instead of displaying “nan”). The linked writable point will drop down to the next-highest priority arrayed input (or fallback) for control, instead of also displaying “nan”.

To preserve backward compatibility, support requires that you edit the proxy point’s facets and add an additional entry, specifying a Key, Type, and Value. Depending if Numeric or Enum, the following facets are supported:

In the Config Facets dialog when editing a point’s facets to add an entry, you must directly type in the needed Key value (not available in the Key drop-down list). See Figure 5 and Figure 6 for an example of adding the “nanIsNull” key for a numeric.