OPC Item Path in UDT

[gustavo.chamorro]

Hi,

I would like to communicate with my PLC via Modbus TCP. As I will have several variables, to optimize and facilitate, I thought about using UDTs.

However, I encountered some difficulties:

1- I am totally dependent on my address. When I register it on the gateway, I cannot prevent it from appearing at the end, which defeats the purpose of using a UDT. If I have another PLC, I cannot reuse the UDT tags and need another UDT.

If I change the address, I will have to change it in the PLC, the gateway, and the UDT. If it were passed at the end by parameter {pump1}, I would use a single UDT, always associated with pump 1 or pump 2, not the address. For the same reason, I did this in my MQTT UDT.

Ex:

2 - Looking at the forum, I found two ways to do it, but I don't know which one is best. Whether it's creating it through the gateway or creating it directly in the tag. Even so, it comes back to the UDT issue, which I'm lost on.

and creating through the gateway, I couldn't read two consecutive addresses ;-;

Created at the gateway:

Directly in the tag:

It's very likely that it's something simple that I'm not seeing.

[amarks]

I would create your base UDT and then create a UDT that uses it as the parent datatype. You could add a parameter for each OPC item path address on the child UDT. The structure of the UDTs would then remain the same and could use the same templates/views.

[robertm]

Nm

[michael.flagler]

When connecting to Modbus devices, it's generally recommended to avoid using the Modbus mapping in the driver configuration. Instead, use the manual addressing approach in Ignition documented here:

Modbus Addressing | Ignition User Manual

Also if there's a pattern in the modbus addresses like there's a base address for a UDT set of tags with an offset, you can do parameters like this:

ns=1;s=[{deviceName}]HR{baseAddress+9}

Where your device name parameter is ET_ASSIS and the base address parameter is 6000.

[David_Stone]

This is also how I’ve done Modbus UDTs, it means you can also manually override individual tag addresses that don’t match the pattern for any reason, and that override is per device.