Passing data into a Tag

Hi there,

I am new to ignition so please bear with me!
I have created a UDT tag called pump and in that tag I have 3 integers which connect to the PLC via OPC. The three values makeup the data that is associated with my pump. So far so good. Now I want to make the OPC path dynamic so that if my OPC path changes I just modify the address in one place and all the tags change. But I can’t seem to be able to point a parameter of my UDT at an existing tag, in this case my default tag would be a string containing the address of the OPC server and the instances of my UDT’s would then reference this address.

I hope that makes sense and thanks for your help.

You need to parameterize your UDT tag paths.
Start here for 7.9.x
Or here for 8.x

Hi there,

Thanks for your reply. I have seen the links that you pasted but I’m not sure these help me. I can put a parameter into the OPC server path no problem but when I create an instance of the UDT I can only type text into the parameter value (i.e. hard code it). I want the value in the parameter to come from another tag but I can’t seem to do that.
I want to store the address of the OPC server in one tag on the system and if I change that tag value then all the UDT OPC server addresses referencing that tag change.

Another option I thought of was that rather than using a parameter I can create another tag inside the UDT which is a reference tag. I can then pick up the address of the OPC server (by referencing a global tag) but how do I pass the value of this tag inside the UDT to another tag as the OPC server address inside a UDT.

Thanks in advance
Kevin Lee

Not sure you can do what you want purely with expressions. You may have to script it with system.tag.edit* or system.tag.configure*.

Hi there,

Thanks for your response. I haven’t looked at that kind of scripting yet. Is there anywhere I can read up on the commands you are talking about and see whereabouts I would add such a script?

I also assume that I would need to have a line of script for each device to change or would it be possible to pick up a collection of tags. So the script would be from 1 to numb of tags in a collection rather than explicitly coding each tag.

Kind Regards