Help! Cannot browse to OPC object in MVE

[Tim Morton]

I currently have the following:
LabVIEW 8
DSC module
Industrial Automation OPC Servers (formerly part of Lookout)

I'm having trouble binding my shared variables to addresses in my PLC (defined as an object within Industrial Automation OPC Servers). I have tried adding an I/O server to my project, but I cannot browse any deeper than "National Instruments.OPCLookoutDrivers" when I do. When I attempt to bind a variable to the I/O server I can only bind to items within "NI OPC Client Status", and not to my PLC object or any of its addresses.

However, I can browse to my PLC addresses if I use the DataSocket Select URL vi. Can I manually cut and paste an opc datasocket URL into the binding field in the variable editor?

Previously, with version 7.1, I had no difficulty browsing to my PLC addresses in the Tag Editor. I have tried importing from my old scf files, but the imported variables do not seem to be bound to anything at all.

I'm pulling what's left of my hair out over this, and debating moving away from DSC to datasockets. I keep hearing that DSC is more efficient for communicating with a large number of data points (I have hundreds to deal with), but if I cannot get DSC working under version 8 then I may just abandon it.

[Lorenz03Tx]

There was an issue with the 8.0 release and Lookout Protocol Driver OPC support.

That issue has been fixed in the 8.1 patch, and I would strongly recommend patching your 8.0 installation.

However, you can also manually enter the address as well. This is best done, by browsing to one of the status items. Then remove the last part of the text for the status item and add the last part of the DS URL that represents the PLC address from the LPD.

Hope this helps.
-Lorenz

[Tim Morton]

Thank you! I've really been pulling my hair out over this one, and I hadn't heard about the patch yet. I'll dig around and see if I can locate it. In the meantime I'll try your suggestion to add the items manually. Thanks again!

[Lorenz03Tx]

    In your first post you mentioned that you had a few hundred data points you need to access with OPC. The Variable Node (the node on the block diagram) performance doesn’t scale that high in the 8.0x release. However, it is true that the OPC I/O Server should be much more efficient that the Data Socket OPC API. This leaves you with two possible approaches to efficiently access hundreds of OPC points.

A) If you want logging/scaling/ or configuration on those points:
1) You can use the multiple Variable Editor to create a variable for each point you are interested in with the desired configuration.
2) Then, use the Shared Variable refnum (the purple wire) with the Data Socket API (you can wire the refnum right into the read and write primitives).

B) If you just need the raw points:
Use the Data Socket API to bind directly to the points under the OPC I/O Server you created in the project (the PSP URL).

In both cases you use PSP (with Data Socket) to talk to the Variable Engine, and the Variable Engine will use OPC to talk to LPD. It seems a little indirect but you should see significant performance improvement over using Data Socket with OPC to the LPD.

-Lorenz
Sorry for all of the TLA (Three letter acronyms)