Creating proxy points

As with device objects in other drivers, each Lon device has a Points extension that serves as the container for proxy points. The default view for Lon points is the Lon Point Manager. You use it to add Lon proxy points under any Lon device.

The Lon Point Manager works differently than other driver Point Manager views. When toggled out of learn mode (Database pane only), the Add button is unavailable for manually adding proxy points.

The set of network variables (nvs, ncis) associated with each device type determine the Lon proxy points that are available for the device. Once you learn the device, this information is known to the system, and available in learn mode. If you add proxy points offline, this information is also known once you associate a Lon Xml File (extension .lnml) with the parent Lon device. No point discovery job is available for specific data items in any Lon device.

Once the station database contains the information for a specific device, you can add input and output network variables (proxy points) to the device.

This procedure is basically the same for the local Lon device and dynamic devices. Where the local Lon device proxy points differ has to do with how you can use them. Depending on the item selected, the default point type is either writable or read-only, as follows:

nvi (read-only, that is NumericPoint, EnumPoint, BooleanPoint, or StringPoint)
nvo (writable, that is NumericWritable, EnumWritable, BooleanWritable, or StringWritable)
nci (read-only, that is NumericPoint, EnumPoint, BooleanPoint, or StringPoint)
NOTE: Point type selections for local nvis and ncis are limited to read-only types (meant to be written externally, that is, outside the station). In the case of local nvos, only writable point types have any practical application, as only the station is capable of writing to its own nvos. This is the reverse of the default point type selections when creating other Lon proxy points.

Perform the following steps:

Double-click the Lon network node in the Nav tree.
The Lon Device Manager view opens.
In the row of the Database pane representing the device, under the Exts column, double-click the points icon ().

The Lon Point Manager view opens.
To make sure the view is in split-pane (learn mode), click the Discover button.

The driver lists device network variables (nvis, nvos, and ncis) in the top Discovered pane. Each row discovery job runs and the table represents one Lon proxy point candidate with each network variable (nv) occupying one row.

A plus (+) to the left of a variable identifies a structured SNVT (Standard Network Variable Type) with multiple data properties. By default, the first data property in the SNVT structure appears on top.
Click the plus (+) to view the additional data properties.
Click to select the data items you wish to proxy.
For an nv implemented as a structure, you may need one or more secondary data properties instead of (or in addition to) the first top data property.
To add the selected items in the station as proxy points, choose one of these methods:
- Drag the selected points from the Discovered pane to Database pane (brings up an Add window).
- Double-click an item in the Discovered pane (also brings up an Add window).
- Click the Add tool () in the toolbar.
- Click to select in Discovered point , then press the letter a (quick add).
If you either dragged or double-clicked the selected points, the Add window opens. The quick add option (select the row and click a) bypasses the Add window. This option is for points that do not require further configuration.

If the Add window opens, edit the point configuration, and click OK.

In some cases, you may need to edit a point’s facets or even conversion type. When you add a Lon proxy point, the driver pre-selects a default point type. Often, this data type (category) is either numeric or enum, and less often, Boolean or string. A Lon proxy point supports default conversion between data types. This means that when creating a proxy point, you can select another data type, if the selection would be useful for your station’s application. The driver supports changing point type (category) for local Lon device points as well as for dynamic device points.

For example, if when adding a proxy point for an nvo implemented with SNVT_Switch, you are interested only in the state element as either false (off) or true (on), and you do not anticipate a null value, you can select a Boolean Point instead of the pre-selected Enum Point.

Figure 5. Changing point type when adding Lon proxy point

This would allow you to link the Out of the proxy Boolean Point directly to a Logic-type kitControl object without using an intermediate conversion object (StatusEnumToStatusBoolean). The updated proxy point would convert enum ordinals 0 to false, and 1 to true.

The table below shows how default Lon proxy point conversions are handled between data types.

LonData element type to proxy point data type, default conversions

LonData element type	Proxy point type	Conversion method	Setup notes
Numeric	Boolean	False = 0, True = 1value <=0 = False, >0 = True	—
	String	Converts between string representation and numeric values	—
	Enum	Numeric is enum ordinal	Add facet EnumRange
Boolean	String	True = true, False = false	—
Boolean	Numeric	False = 0, True = 1value <=0 = False, >0 = True	—
Enum	Numeric	Numeric is enum ordinal	—
	Boolean	True to ordinal 1, false to ordinal 0.	—
	String	Read/Write enum tag	—
String	Numeric	Converts between string representation and numeric values	—
	Enum	String is enum tag	Add facet EnumRange
	Boolean	True = true, False = false	—

Also, when you add a proxy point under a Lon device for an nvi, nci, or cp, the Add window defaults to a writable type, for example NumericWritable or EnumWritable. Before creating the proxy point, you may wish to change it to a read-only point type (if you wish to monitor only).

When you have Lon proxy point(s) configured properly for your usage, click OK.
The system adds the proxy points the station, and displays them in the Database pane. If you are online, points poll for current values. If you are working offline, all proxy points appear down (yellow).