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Read OPC server data from PLC

seg_rolgarseg_rolgar
edited September 2021 in PLCnext Technology & PLCnext Controls
Hi everyone!
I have running on my PLC (AXC F2152) an OPC server where I can write several variables of my PLC program. It works fine, I can access to it from an OPC-UA client and to see the data. Now I was wondering if it is possible to connect another client to this OPC server (for example another PLC) and write another new data on it. Then I want to read this new data from my AXC F 2152.
Is there any way to do this? I was checking the forum but only found threads related to OPC as Server to write data.

Thanks in advance,

Best regards,

Comments

  • Martin [PLCnext Technology Team]Martin [PLCnext Technology Team]
    I'm not quite clear on the requirement here (sorry):

    There are three devices:
    1. AXC F 2152
    2. OPC UA client device
    3. another OPC UA client, e.g. a PLC (type unknown)

    Device 2 needs to exchange data with device 1. This has already been achieved using OPC UA.

    Device 3 also needs to exchange data directly with device 1? Is that correct?

    If that's correct, then if device 3 has OPC UA client capability, it can connect to the OPC UA server on device 1 at the same time as device 2 is connected, and both device 2 and device 3 can exchange data with device 1 at the same time.

    PLCnext Control devices do not have OPC UA Client capability included, so if device 3 is a PLCnext Control device, then you may need to consider other ways to meet the data exchange requirement (e.g. using Profinet).
  • seg_rolgarseg_rolgar
    There are two devices:
    1. AXC F2152
    2. Another OPC UA client, e.g. a PLC (type unknown).

    The other device that you mentioned is a test client in order to check the opc ua Server of PLC works fine.

    So, I want to use device 1 (AXC F2152) as OPC server and exchange data with device 2 using OPC-UA server, but both must be able to do both operation, read and write.

    Although, if I understood the last statement, the device 1 (AXC F2152) has only the possibility of to be OPC server, not OPC client being impossible read data wrote by the other device in the OPC server.
    Can you confirm this?

    Thanks,

    Regards.
  • seg_rolgarseg_rolgar
    I saw this on the forum:
    https://www.plcnext-community.net/en/discussions-2-offcanvas/opcua-client.html

    May be it is possible to do what I want to.
  • Frank Phoenix Contact Deutschland SupportFrank Phoenix Contact Deutschland Support
    Hi seg,
    using any other (external) UA Client SDK you could implement the capeability by yourself.

    Depinding on your timeline it might worth waiting for the release of 2022.0 (end of November).
    With this version we will integrate OPC UA Pub/Sub, which seems to be exactly what you are looking for.

    Frank
  • Martin [PLCnext Technology Team]Martin [PLCnext Technology Team]
    If the second device (2) is an OPC UA client, then it can read and write data on the OPC UA Server (AXC F 2152). The AXC that is hosting the OPC UA server can also read and write values from/to variables in the OPC UA server. So, data can be exchanged between the two devices via OPC UA as follows:

    - The AXC F 2152 defines the data that will be available in the OPC UA server.
    - The AXC can "write" data to the other device by writing values to variables in the OPC UA server, which the other device (OPC UA Client) reads.
    - The AXC can "read" data from the other device by reading values from variables in the OPC UA server, which the other device (OPC UA Client) has written.

    Does this solve the problem?

    If the other device has Profinet capability, then may also be possible to exchange data between the two devices via Profinet.
  • seg_rolgarseg_rolgar
    Hi, yes, it solved my problem.
    Just one more question. If the other device modify a variable on the OPC-UA server, how can I read this variable from AXC? Change appears instantly right?

    Thanks for the help!
  • Martin [PLCnext Technology Team]Martin [PLCnext Technology Team]
    If the other device modify a variable on the OPC-UA server, how can I read this variable from AXC? Change appears instantly right?
    Yes, you're right. To create a tag in the OPC UA server on the AXC F 2152, you must mark a variable with the "OPC" attribute in PLCnext Engineer. If the value of that variable is changed by an OPC UA client, then the new value will appear in the PLCnext Engineer project immediately. In this way, the AXC F 2152 is able to read a new data value from the other device immediately after the other device writes that new data value to the OPC UA server.
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