New (and Edit) Bacnet Descriptors

Descriptors configure import and export jobs.

The Export Table provides a set of descriptors. Each has the same set of properties, although, depending on the descriptor, the Type property and BACnet Writable properties may be unavailable for editing.

Figure 200.   Bacnet Analog Input Descriptor window
Image

To open one of these windows, expand Config > Drivers > BacnetNetwork > Local Device, double-click Export Table, click New and select the type of descriptor from the Type to Add drop-down list.

Property Value Description
Name drop-down list of BACnet objects
Identifies the object (point, export folder, etc.) including an Object Id and Instance Number or property identifier, which ensures a unique name.

This name is in the format: objectType_<instance number> For example and Event State may be named: AHU1–Frz_Stat-eventState.

Refer also to Object Id, Instance Number.

Object Name text in the format name.name.name.name (default includes the entire component path in the station using period (“/) delimiters between parent.child levels)
Identifies a BACnet object. This name should be unique within this specific device.

For components, this name includes the entire component path under the station’s Config using period (.) delimiters between parent.child levels. This enforces (externally) the BACnet requirement for unique names for all objects in a device.

For a proxy point, this is the default name in the station.

You can shorten or edit Object Name, however, each Object Name must be unique among all server descriptors under the Export Table.

Type read-only or a drop-down list
Identifies the type of BACnet object, for example, Analog Input, Analog Output, Calendar, Schedule, Structured View, File, Trend Log, BooleanWritable or other.

Writable components typically offer more type selections than read-only points, such as:

  • Two read-only: input or value type, e.g. Binary Input or Binary Value object.
  • Two writable: output or prioritized value type, e.g. Binary Output or Binary Value Prioritized object.

    The screen capture shows an example of type selections when exporting an NdioBooleanWritable point.

This property is dimmed if the export Type is read-only, such as for Analog Input or Binary Value.

Object Type read-only
Reports the type of object.
Inst Num number in the range from 0 to 4194302
Provides a unique number to combine with a device’s Object Id. Together, these properties form the Device Id.

The Instance Number must be unique within the BACnet internetwork for each entity: components, devices, points, schedules, analog inputs, files, groups, multi state inputs, trend logs, SVO (Structured View Object), etc.

The driver automatically increments this value when adding multiple entities.

Refer to Object Id.

Export Ord ord (defaults to the format used is the numeric handle instead of slot, which is better if the source object gets renamed)
Defines the location of the source component or file using standard file Ord notation. In an Edit window, you can access a more meaningful ord by clicking the right-side folder control. This produces a popup Select Ord window, showing the component’s location in the station’s component tree hierarchy.
Description text
Provides additional information, which could include the camera’s geographical location or other unique information.
BACnet Writable read-only or an array of check boxes
For writable types, provides an array of check boxes that configure the specific priority levels externally exposed to BACnet for the purpose of accepting writes. Included are all controls to clear or select.

This property is dimmed if the export Type is read-only, such as for Analog Input or Binary Value.

Each priority level (1-16) that you enable for BACnet writes results in that InN input on the source component to be linked to this Bacnet export descriptor component. These links appear as nubs when viewing the source writable point in its wire sheet view.

Do not select any priority level already linked or in use by the system, otherwise control contention occurs.

After you add a BACnet export descriptor you can configure additional properties accessible in its Property Sheet, along with those that are available in the Add and Edit windows.