Adding multiple parameters together in an expression tag not working

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1

Im attempting to indirectly address structures of strings in a UDT

tag("[edge]P1_540_PLC/UnitId 1/1_INT100-1_INT1000/1_INT" + ({Pump_IntNumber} + {Interval_Count}))

I have a list of modbus addresses 100, 200, 300, etc (pump_intNumber) that im attempting to add the offset addresses to to make addressing these OPC modbus tags easier but for some reason this string generates this error:

[null, Error_ExpressionEval("Error parsing/subscribing path '[edge]P1_540_PLC/UnitId 1/1_INT100-1_INT1000/1_INT100{Interval_Count}' in tag() expression."), Thu Sep 04 15:41:10 PDT 2025 (1757025670952)]

Any ideas how to get around this? i can add a literal number, but i cannot add two parameters together. For clarification my end goal is to end up with a [edge]P1_540_PLC/UnitId 1/1_INT100-1_INT1000/1_INT100, 101, 102 etc.. number.

2

I can't quite figure out what you're trying to do, but should you be converting the sum to a string, like this?

"ABC" + toStr({[~]myInt1} + {[~]myInt2})

3

Let me try and explain a little deeper,

I have a list of tanks and pumps im looking to quickly and easily template based on modbus addresses, Modbus address 100 - 125 = tank 1 modbus address 200 - 225 = tank 2 and so on.

each address 100, 200 etc has an offset that corresponds to a sensor input, (101 is valve 1, 102 is valve 2, 103 is level and so on) all of the tanks are the exact same. So im looking to add two different parameters Parameter 1 is offset for the “main” tank number (100) plus the individual register offset (1, 2, 3 etc)

So the end tag should look like this [tag goes here]{PumpInt_Number} + {Pump_offset_tag} Adding these two parameters together should equal the final register number {100} + {3} = 103 however for some reason only the first parameter is evaluated, the second is not.

Edit: I realize that i accidentally said string datatypes, these are expressions that are evaluating to tag paths, not strings.

4

Easiest for me is just create two template properties called index and offset, and a custom property called final. Bind final to index+offset. Pass the values of index and offset to your template.

Then a widgets binding is an indirect of [provider]statictext{1} where 1 is your custom property final.

5

That will work, thanks for the help.

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