Configuring an OPC Group Object

To add a group object to your OPC data source hierarchy

1. Select the new data source object, right-click it, and then click Add OPCGroup Object on the shortcut menu.

   A new object is created in the hierarchy tree and is named New_OPCGroup_000 by default. Rename it, if desired. You are allowed to add up to 100 new group objects.

   Note: Each group or topic must be uniquely named for the data source associated with it.

   The New_OPCGroup_000 Parameters configuration view (right pane) is displayed.

2. Configure the new group object according to the following option definitions:

   • Device Group Name – Name of the topic that DDE or SuiteLink clients of OI Gateway connect to in order to access items at the OPC group. Default value is the concatenation of the OPC data source object’s name and the group object’s name (this cannot be edited).

   • Update Rate – Value (in ms) used by OI Gateway to update the OPC group. Minimum/maximum range is 0 to 2147483646 ms. If the OPC server supports it, zero (0) update rate means the data source sends data changes immediately. If the server does not support zero update rate, it typically returns a message including information about its fastest possible update rate. Default value is 1000 ms.

     The update rate can also be adjusted at run time by setting the $SYS$OPCUpdateInterval system item.

   • OPC Item ID Prefix – String prefixed to all item names added to the OPC group. Default value is blank. The syntax to use the prefix is <Prefix>.<Item>. For example: If the item prefix is 40 and the Item name is XYZ, the item requested from data source is 40.XYZ

   • Use Group Name as Access Path – Provides control over the OPC Access Path for items added to the OPC group. When checked, the name of the OPC group object is used as the OPC Access Path for all items. When unchecked, the default (blank) OPC Access Path is used. Default value is unchecked.

   • Read Only – Check this box to make all items connected through the OPC group read only. This qualification is in addition to any read-only condition that the OPC server imposes. Unchecking this box only removes OI Gateway-imposed read-only qualifications. In other words, items inherently read-only in the data source remain so. Default value is checked.

   • Demand Read After Poke – Provides an option to read an item immediately after a write transaction on the item. When checked, a read transaction is performed on the item whenever it has a write transaction irrespective of the subscription group interval. When unchecked, the value of the item is updated at the specified subscription interval after a write operation on the item. Default value is unchecked.

   • Browse OPC Items button – Opens the OPC browser, in which you can select items directly from the OPC server.

OPC groups are used to model the behavior of OPC servers. You cannot add items directly to an OPC data source, but must add them at the group level.

To add a group object to your OPC UA data source hierarchy

3. Select the new data source object, right-click it, and then click Add OPC UAGroup Object on the shortcut menu.

   A new object is created in the hierarchy tree and is named New_OPCUAGroup_000 by default. Rename it, if desired. You are allowed to add up to 100 new group objects.

   The New_OPCUAGroup_000 Parameters configuration view (right pane) is displayed.

4. Configure the new group object parameters.

   1. Device Group Name: This parameter is configured on the hierarchy tree, and is displayed in a non-editable text box in the parameters configuration pane.

   2. Update Rate: Expressed in milliseconds, this parameter controls the fastest rate at which updates are sent from the OI Gateway to the client. The default value is 1000 ms. The minimum value is 0 ms. The maximum value is 2147483646 ms. This parameter is hot configurable.

   3. Read Only: When selected, all items connected through the OPC UA group are read only. This parameter is hot configurable.

5. Configure the Device Items by one of the following methods:

   1. To browse OPCUA server items and populate in Device Items tab, click Browse OPCUA Server to browse OPCUA server items and populate in Device Items tab. For more information, see Item Browsing in the OPC UA Server Namespace.

   2. Configure Device Items. Click the Device Items tab and add item names and references. For more information, see Configuring Device Item Definitions.