Professional OPC
Development Tools

logos

Online Forums

Technical support is provided through Support Forums below. Anybody can view them; you need to Register/Login to our site (see links in upper right corner) in order to Post questions. You do not have to be a licensed user of our product.

Please read Rules for forum posts before reporting your issue or asking a question. OPC Labs team is actively monitoring the forums, and replies as soon as possible. Various technical information can also be found in our Knowledge Base. For your convenience, we have also assembled a Frequently Asked Questions page.

Do not use the Contact page for technical issues.

Problems Writing and Reading Values

More
28 Oct 2018 06:40 #6799 by support
Hello.

For reading: Normally, the read is performed with "maximum age" (defaults to 1 second), which can lead to reads from server cache or using client's memoized value. if you want to be sure that you are reading the most up-to-date value from the server, you need to specify a read from the Device. This can be done in DAReadParameters that are passed to the method; in COM, you will have to switch to the ReadMultipleItems method, because there are no method overloads, and the ReadValue COM method does not allow to pass DAReadParameters in.

For writing: Are you sure that you detect any possible errors thrown by the WriteValue call? QuickOPC always throws an error when the OPC Server returns a failure code from the OPC write operation. If no error is thrown (and you do not ignore them), then the problem is practically guaranteed to be on the server side.

Best regards

Please Log in or Create an account to join the conversation.

More
26 Oct 2018 10:11 #6796 by Alessandro Tessari
Hi,
i'm having problems reading and writing values in an application i've developed, seems like some values do not refresh.

The communication in the application is really simple, i use client.ReadValue and client.WriteValue calls only.
Sometime happens that the value returned by the ReadValue function is not what i see in the OPCserver and, similarly, the WriteValue function fails to update the value in the OPCserver.
The strange thing is that it happens only for some items, and not every time.
For reference i'm using version 5.51.465.1 in a vb6 application.

Am I missing something??
Could it be caused by a different configuration on the OPCserver items??
Any suggestion on how to solve the problem wuold be really appreciated. If more details are needed feel free to ask.

Thank you in advance!!
Alessandro

Please Log in or Create an account to join the conversation.

Moderators: support
Time to create page: 0.151 seconds