Siemens OPC UA STRUCT: read OK - can we write back without binding each member?

[viherlauri]

Hi! We’re using FUXA with a Siemens PLC OPC UA server.

We have an array-of-struct AikaBlokit. Each element [0] / [1] is a STRUCT with members: bittiMuuttuja (BOOL), integerMuuttuja (INT16), realMuuttuja (REAL), doubleRealMuuttuja (LREAL), stringMuuttuja (STRING).

Our custom SVG widget is bound only to the parent struct node AikaBlokit[0] (NodeId ns=4;i=15).
Reading works as expected: FUXA decodes the struct value and the widget receives it as a JavaScript object, so it can render all struct members without binding individual tags.
In the tag list, the parent node shows as Type String and Value [object Object], while the member nodes are normal scalar tags.

Question:

Is it possible in FUXA to write the whole STRUCT back to the PLC by writing to the parent struct node (AikaBlokit[0] / AikaBlokit[1], e.g. ns=4;i=15) as a single OPC UA Write, without creating and binding separate FUXA tags for each member?

This is important for us because our real PLC structs contain dozens of members. Creating and maintaining a separate FUXA tag for every member is not practical (too much manual work, hard to maintain, and error-prone). We need a way to edit the struct using only the parent struct node.

Ideally, we would also like to bind the widget to the array parent (AikaBlokit) so we don’t need separate tags for [0], [1], [2], etc.

[MatthewReed303]

Here is the opc driver for Fuxa

https://github.com/frangoteam/FUXA/blob/master/server/runtime/devices/opcua/index.js

You may be able to get the device instance in you widget via JS

[HytKys]

About OPC UA and Siemens PLC.
On firmware 4.7 the Siemens S1200 series PLC the OPC UA server was added with capability to provide access to complicated data structures (Array, Struct) in one tag. That feature is not in the previous firmware versions.