From: R.
Sent: Monday, December 05, 2011 8:41 PM
To: Zbynek Zahradnik
Subject: RE: Deadband error reading tags
Zbynek,
I sent this version to the customer and it did resolve the problem.
Thanks.
R.

From: R.
Sent: Monday, December 05, 2011 4:35 PM
To: Zbynek Zahradnik
Subject: RE: Deadband error reading tags
Zbynek,
Thanks for sending this. I still have not received a confirmation from the customer regarding your two questions. Hopefully this will take care of the issue.
R.

Renee,

I went ahead, and implemented a workaround, based on assumption that the error code is indeed OPC_E_DEADBANDNOTSUPPORTED. The new build is 5.11.496.1 [.....]

Best regards,

..... Thanks. I think the answer to #1 is yes, but I will verify both questions with the customer and let you know.

R.

R.,

First, let’s establish the facts.
1. I assume we are referring to this server, right?: <a href="www.opcfoundation.org/Products/ProductDetails.aspx?CM=1&....aspx?CM=1&RI=836&CU=1 .

2. Is the error they are getting the following one? " The item does not support deadband. ”? It would be OPC_E_DEADBANDNOTSUPPORTED then, numeric code 0xC0040400L (3221488640 or -1073478656). Please confirm. I am making this assumption for the remainder of this email; if the error is different, the answers could be different, too.

To your question: Deadband does not actually apply to Reads, only to Subscriptions, and therefore you cannot set it in the ReadXXXX method calls. Internally the component must create an OPC group for the items, and that’s where the error could be coming from. On OPC level, creating a group always involves specifying some deadband, there is no way around it, and we are passing an internal, small, but non-zero to groups that are used for this purpose. It might be this non-zero deadband that causes the issue. Technically we could pass in zero, but there are reasons why we are not doing that by default.

Unfortunately (seems that by omission), it is not currently possible to change this non-zero deadband to something else from the application code (through our API). I will make a note to correct this in future version. For now, I will add extra code to react to this error by re-trying with zero deadband.

Please check the above listed facts with the customer, and in the meantime, I will prepare this workaround. I really must know with certainty the numerical error code they are getting, otherwise the workaround I prepare will not help.

Best regards,

<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt">From:<span style="font-family: "Tahoma","sans-serif"; font-size: 10pt"> R.
Sent: Thursday, December 01, 2011 9:08 PM
To: Zbynek Zahradnik
Subject: Deadband error reading tags

Hello Zbynek,

I had a call from a customer who is using Data.NET 5.11 with Cisco AxS4-ICCP OPC server. They are receiving errors using the ReadItem and ReadMultipleItem calls that deadbands are not supported by the server. They talked to Cisco and confirm that the server does not support deadbands.

My thought was that she could just pass in a null value for that parameter, but I do not see in the API, where the deadband is being set in the ReadItem or ReadMultipleItem calls. Is this something that is being passed behind the scenes?

Thanks in advance,
R.