Using UDS OPC with String tags returns empty Tags

[Former Member]

I am Using an OPC Simulation Server (KEPWare OPC 5.6.122.0) and UDS 4.0 and configured some Tags with String values.

These Tags can be read correclty via different OPC Clients (e.g. Matrikon OPC Explorer).

The tags are named without any special characters and the path also only contains standard characters.

Tags with integer values can be read by an MII Tagquery without any problems, but the string values are not listet when the are tested. and yontain no values?

Does somebody has an idea what i could inspect further?

Is there anybody with the same effect?

Thanking you very much for helping me

Best regards

Thomas L.

[former_member202228]

Hi Thomas,

Try to build an Alias for the particular UDC you're using.

Click the Alias button > Select UDS from menu bar > Browse

It will ask you to browse a set of(un)masked tags and build the alias for you.

The Alias is then built in the upper part of the window. Try select from the tree structure the groups you find there, and drill down to indivitual tags in the groups. In the right upper part of the window will appear some tags in a grid-like form. If they're highlighted RED, the format is not understood by the connector (i.e. BIT tags)

There are dropdowns if you click the TYPE fields, with the following items to be selected:

- VarChar

- Integer,

- Double,

- TimeStamp

- Other.

I guess your string tags will correspond to a VARCHAR type. If you do not define the alias (and select the corresponding cache mode for the connector) and define the data conversion as understood by the UDC, the conversion fails and you get empty values.

Integer values can be read by default because the notation is the same in Kepware and UDC. I guess you're having the same problem with the floats (since the conversion to double is not implicit).

I'm usually asking from the PLC programmers to define the right type of tags in the machines as they start to define the data-flow and connectivity , so that I won't have to configure thousands of items in alias files. Unfortunately, sometimes you have to work with systems you cannot modify.