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Old August 31st, 2005, 10:41 AM   #1
SoggyFisherman
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Problem setting RSLinx OPC UpdateRate with VBA

Hello everyone. Long time listener, first time caller.

I'm having a problem with RSLinx OPC in an Excel VBA application. I have posted this over on the Rockwell Software site forum, but from past experience I don't think I'll get any solutions over there. There is a much better pool of resources over here, I think.

The application is reading a stand-alone rack of Allen-Bradley Point-I/O (1734 series) over Ethernet/IP using RSLinx OEM. I'm using the OPC Automation Wrapper from Software Toolbox to access the OPC objects in VBA (why does A-B only distribute an Automation Wrapper with SDK?). Everthing is going well except that I am not able to set the Update rate for the OPC group.

The program gets the OPCGroups collection and adds a group object which I named "AIO_Group". The problem is when I set the Update Rate for the OPCGroup object (AIO_Group.UpdateRate) to say 1000, the actual rate drops to 1. I confirmed this by reading the UpdateRate property later on in the program, and by monitoring the OPC Diagnostics in RSLinx. Does anyone know of any special handling for this property?

The strange part is that if I take out the group UpdateRate statement and add one to set the OPCGroups collection object DefaultGroupUpdateRate property, it works fine. But that way I lose the ability to set individual group update rates (I want one at 2 seconds and one at 500ms).

Has anyone done this successfully with RSLinx? Thanks.

Don

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Old August 31st, 2005, 11:17 AM   #2
Bob O
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Not sure if this will help or not.

With help over at MrPlc I was able to HACKED through this and pull data from an MS Access table and place it into an Excel spread sheet that then sent it to my ML1500 every 5 sec using a hotlink . If you like I can post what I have and you can take a look.
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Old September 1st, 2005, 08:38 AM   #3
SoggyFisherman
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Thanks for the reply. It would be great if you could post your previous spreadsheet, since I am always interested in other people's techniques. You mentioned that you used a hotlink, so I am assuming it was a DDE connection to the PLC. In my project I am actually moving away from DDE to OPC because of latency and stability problems. This problem isn't a major one, it is just bugging me that I can't figure out why this one feature is not working.

Don
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Old September 1st, 2005, 09:31 AM   #4
Bob O
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Don,
I sent you a pm with my email since the file is 415 kb and the limit is 397.7 kb.

Bob
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