Use UDD to Write Channel Tags to File

[Ascherer17]

Is it possible to access other Channels' Tag data from within a Universal Device Driver profile?

I need to save some Tag data to a csv or text file and am looking at the possibility of using UDD in File Mode to periodically write the data values from a channel (Modbus TCP for example) to file. 

I'm just not yet sure if there's a way to access 'outside' Tag data from within the UDD Channel/profile. 

[pshashipreetham · Accepted solution]

Hi, 

The Universal Device Driver (UDD) only interacts with tags that belong to the same UDD channel/device profile. It does not have visibility into tags from other drivers or channels such as Modbus, Ethernet/IP, etc. So a UDD profile cannot directly read another channel’s tag values and write them to a file.

Recommended approach

Use one of the following supported options instead:

Option 1 – DataLogger plug-in (recommended)
This is the simplest method if the goal is exporting tag values to CSV.

Steps:

1. Enable the DataLogger plug-in in KepServerEX.

2. Create a Log Group.

3. Add the tags from the required channel (e.g., Modbus TCP).

4. Configure the output format as CSV or text file.

5. Set the log trigger (periodic or on change).

This approach is designed exactly for writing tag values to files.

Option 2 – Local Historian + export
Store values using Local Historian, then export the data periodically to a file or database.

Option 3 – External client (OPC UA / OPC DA)
Use a small external script or application that reads tags from KepServerEX and writes them to a file.

Summary

UDD is intended for custom protocol/device communication, not for accessing internal tag values from other channels. For exporting tag data to files, DataLogger is the intended and supported solution.

Thanks,

[Ascherer17]

I believe this answers the question.  Thank you for the additional ideas. 

I just remembered the "Link" advanced tag also.  Maybe it'd be possible to use a Link tag to copy data values into the UDD channel?