OPC UA instance specifier to access single value of array

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Steven Chen asked Aug 24, '23 Luciano Cavallero answered Sep 22, '23

OPC UA instance specifier to access single value of array

Hello,

I would like to re-open this topic: Using OPC UA to connect Fanuc robot - FlexSim Community

In conclusion, build-in Emulation GUI tool doesn't support specifying array index, we need to use internal Emulation in Process Flow.

So we can set node id to following format, where the %s is array index.

ns=2;s=Model;DiscreteInput[%s]

But it fails to read correct value of array, which is always zero.

I use OPC UA ANSI C Demo Server (Windows) as OPC UA server for testing.

UaExpert to modify node value, I set all boolean values to true.

Could you find out what is wrong in my model?

opcua_instance_v22.2.fsm

Software Version:

FlexSim 22.2.4

emulation opcua

01.png (37.5 KiB)

opcua-instance-v222.fsm (28.4 KiB)

· 12

Jeanette F ♦♦ commented · Aug 25, 2023 at 05:18 PM

@Luciano Cavallero, @Tancredi Canonico, @Fiorenzo A, can you please take a look at this emulation-related question?

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Luciano Cavallero commented · Aug 28, 2023 at 07:06 AM

Some OPC UA Server doesn't support direct access to a single element of an array ( the 'index range' functionality is not supported): please check if your server support this feature.

To avoid problem, if possible, transform your array of boolean into a set of single bool variables.

NOTE: the UaExpert client read and write all the array elements at once.

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Steven Chen Luciano Cavallero commented · Sep 01, 2023 at 09:34 AM

I believe there is nothing to do at server side, because I am able to use Python to specify array index. I use UserCommand to run this Python code.

from opcua import Client

def read(url, node_id, array_index):
    client = Client(url)
    client.connect()
    value = client.get_node(node_id).get_value()[int(array_index)]    
    return value

My goal is to do the same thing with emulation tool or internal emulation in process flow.

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Jason Lightfoot ♦ Steven Chen commented · Sep 06, 2023 at 05:14 PM

That expression seems to be reading the whole array from the server and not the element which would be the part of the node_id expression (in FlexSim including the %s parameter).

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Jason Lightfoot ♦ commented · Aug 31, 2023 at 10:55 AM

Hi @Steven Chen,

We haven't heard back from you. Were you able to solve your problem? If so, please add and accept an answer to let others know the solution. Or please respond to the previous comment so that we can continue to help you.

If we don't hear back in the next 3 business days, we'll assume you were able to solve your problem and we'll close this case in our tracker.

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Jeanette F ♦♦ commented · Sep 11, 2023 at 05:37 PM

Hi @Steven Chen,

We haven't heard back from you. Were you able to solve your problem? If so, please add and accept an answer to let others know the solution. Or please respond to the previous comment so that we can continue to help you.

If we don't hear back in the next 3 business days, we'll assume you were able to solve your problem and we'll close this case in our tracker. You can always comment back at any time to reopen your question.

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Answer 1 · 2023-09-21T06:30:42Z

Luciano Cavallero answered Sep 21, '23

@Steven Chen : alredy in the dev list.

· 1

Steven Chen commented · Sep 22, 2023 at 05:13 AM

Thank you.

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