Using Derived tags to write data from one OPC tag to another

Ignition
1

Hey everyone,

I am trying to pass data from one OPC tag (getting that data from a Modbus device using ignition's Modbus TCP driver) to another (standard OPC tag going to a PLC).

I tried using a derived tag to do this. First, I defined the Source Tag Path as the OPC tag I want to write to. Then I defined the read expression as the OPC tag I would like to pass to the source tag path (i.e. the target OPC tag) using ignition's expression language. I set the write to {value} so I can write the value I'm reading to the source tag path.

However this doesn't seem to write to my source tag as expected. I have confirmed I can write to the PLC tag on its own without any problems, so I'm feeling like I'm stuck on the derived tag write portion of it.

Does anyone have any experience with writing data from one OPC tag to another with derived tags? Thanks in advance :slight_smile:

2

I wouldn't expect anyone to have such experience (except negative), as that is not what they are for.

Consider just placing a tag value change event on the source tag that performs a "fire-and-forget" system.tag.writeAsync() to send all new values to the target tag. (And will include one extra write at tag startup.)

3

Thank you! I didn't think about trying that so I will give it a shot and let you know how that went.

4

It worked pretty smoothly, thank you!

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