UaGateway
1.5.9.466
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When aggregating OPC COM DA servers, UaGateway constructs OPC UA NodeIds for COM DA items, thus making it possible for OPC UA clients to use these items for Read, Write and MonitoredItems. To be used for OPC UA Services, COM DA items do not need to be browsable. If ItemIds are known, the corresponding OPC UA NodeIds can be manually composed and used in OPC UA clients.
When aggregating OPC COM DA servers, an OPC UA NodeId for OPC COM DA items is composed of the COM DA server’s namespace index in UaGateway’s address space and the COM DA ItemId as string identifier.
Example:
For our example, we added Kepware’s KepServerEx to UaGateway as described in HowTo: Add and Connect to a COM Server. By reading UaGateway’s namespace array, we find that the KEPServerEx has received the namespace index 4 (see screenshot).
Together with the ItemId of the item we’re interested in (e.g. Channel_1.Device_1.Tag_3), we can compose the OPC UA NodeId:
Namespace Index: 4
String Identifier: Channel_1.Device_1.Tag_3
Special care has to be taken if the ItemId contains a forward slash character. This character is masked with "//" by UaGateway, so it has to be masked as well when entered manually. The ItemId MyItem.A/B, for instance, has to be replaced with MyItem.A//B when entered manually.
How a NodeId is to be entered manually in an OPC UA client is product specific. In UaExpert, you can manually enter a NodeId for reading by clicking the "+" symbol at the top right corner of the Attributes window (see screenshot).
A dialog window for entering the NodeId will open. Choose "4" as namespace index, "String" as identifier type and enter the ItemId to the input field for the identifier part of the NodeId.
Then click "OK" to read the item. The information returned from the server will then be shown in the attribute window (see screenshot).
Subscribing to an item works similarly: Right-click in the Data Access View and select "Add custom node..." from the context menu (see screenshot).
The same dialog window for entering the NodeId will open. Enter the required information as shown above and click on "OK" to subscribe to the item.