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Writing value and timestamp to OPC DA 2.05a

27 Feb 2024 16:40 #12594 by support

OPC DA 1.0 and 2.0x can only write the value. That would be "WriteItemValue" method in QuickOPC.

With OPC DA 3.0, you can also write value+timestamp+quality.

There is nothing in between (just value+timestamp). Or, the server may decide to it over OPC DA 3.0,m with ignoring the quality. But, you cannot do it with OPC DA 1.0 or 2.0x, there is just no such thing in these specs.

Best regards

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27 Feb 2024 16:06 #12592 by ScottEwine
I am trying to write data to a PI server that supports 2.05a, I am using the following code snippet:

DAVtq dAVtq = new DAVtq();
EasyDAClient easyDAClient1 = new EasyDAClient();


dAVtq.Value = value;
dAVtq.Quality = 192;
dAVtq.Timestamp = dateTime.ToUniversalTime();

easyDAClient1.WriteItem(MachineName, ServerName, ItemID, dAVtq);

It works well in my test environment writing to a simulation server, but at the customer it gives the error below.

No read item or write item function available. The OPC server does not contain a function that can satisfy the combination of requirements (execution method and data source). For example, there is no way to read asynchronously from the OPC Cache if the server only supports OPC-DA 2.0. Also, you cannot write a value-quality-timestamp triple using OPC-DA 1.0 or 2.0.

I understand what the error is saying, and the customer is working to upgrade to support DA 3.0, but if quality is not important, what is the syntax I can use to just write the value and timestamp?

Thanks, Scott

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