OPC Server in Python

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  • F. GEIGER
    #1

    OPC Server in Python

    Hi all,

    I consider writing a control application in Python (realtime stuff would run
    on hw, i.e. a PCI card). If I decide to do so, I'd like to provide access to
    the control app's data for OPC clients. This means writing an OPC Server
    (OPC DA).

    Could I do this in Python too? At the core an OPC Server is a COM server,
    isn't it? Did anyone in this group do anything like that already? And if so,
    are you willing to share your experience?

    Right now I'm trying to get more info about OPC, i.e. there are some
    additional issues like OPC Groups and OPC Items and Browsing etc.

    Any books you would recommend? Other stuff to get me started quickly?

    Any hint welcome!

    Kind regards
    Franz GEIGER



    Tags: python opc
    • Ville Vainio
      #2
      Re: OPC Server in Python

      >>>>> "Geiger" == F GEIGER <fgeiger@datec. at> writes:

      Geiger> Could I do this in Python too? At the core an OPC Server
      Geiger> is a COM server, isn't it? Did anyone in this group do
      Geiger> anything like that already? And if so, are you willing to
      Geiger> share your experience?

      I've written an OPC client (in C++), and used a Wintech OPC client
      library (proprietary). I kinda regret that I didn't use the OPC COM
      interface directly, but I didn't know enough Python at the time (and
      didn't have the Python for win32 book). I guess technically OPC uses
      DCOM, but it ought to work the same way...

      Geiger> Any hint welcome!

      OPC is rather unpleasant. Systems that use OPC should rather use
      CORBA, which is an open standard. Many people in automation industry
      seem to be rather backward in the sense that they consider Windows,
      COM and such things "standard" in some perverse fashion.

      I would expose the variables that you do in your OPC server in some
      more open fashion (CORBA is great w/ Python), and then implement a
      small wrapper application that exposes the variables to OPC clients.


      --
      Ville Vainio http://tinyurl.com/2prnb

        Comment

        • David Fraser
          #3
          Re: OPC Server in Python

          F. GEIGER wrote:[color=blue]
          > Hi all,
          >
          > I consider writing a control application in Python (realtime stuff would run
          > on hw, i.e. a PCI card). If I decide to do so, I'd like to provide access to
          > the control app's data for OPC clients. This means writing an OPC Server
          > (OPC DA).
          >
          > Could I do this in Python too? At the core an OPC Server is a COM server,
          > isn't it? Did anyone in this group do anything like that already? And if so,
          > are you willing to share your experience?[/color]

          I've tried to write an OPC server in Python, just for testing, I had a
          few bugs that I struggled to iron out but in the end I didn't need it so
          I never finished it, but it's definitely doable.
          The nice thing is you could then write an OPC client in Python to test
          it as well...
          [color=blue]
          >
          > Right now I'm trying to get more info about OPC, i.e. there are some
          > additional issues like OPC Groups and OPC Items and Browsing etc.
          >
          > Any books you would recommend? Other stuff to get me started quickly?[/color]

          I would recommend looking at Lab43's LightOPC which is a C
          implementation of OPC code available under LGPL, you can use it as
          examples... Start with a simple server, look at the OPC
          groups/items/browsing later...
          [color=blue]
          >
          > Any hint welcome!
          >
          > Kind regards
          > Franz GEIGER
          >[/color]

          Would be good to hear how you progress...

          David

            Comment

            • F. GEIGER
              #4
              Re: OPC Server in Python

              "Ville Vainio" <ville@spammers .com> schrieb im Newsbeitrag
              [color=blue]
              > OPC is rather unpleasant. Systems that use OPC should rather use
              > CORBA, which is an open standard. Many people in automation industry
              > seem to be rather backward in the sense that they consider Windows,
              > COM and such things "standard" in some perverse fashion.[/color]

              Thanks for the hint, Ville!

              Kind regards
              Franz GEIGER




                Comment

                • F. GEIGER
                  #5
                  Re: OPC Server in Python


                  "David Fraser" <davidf@sjsoft. com> schrieb im Newsbeitrag
                  news:c8a59n$7s5 $1@ctb-nnrp2.saix.net. ..
                  [color=blue]
                  > I would recommend looking at Lab43's LightOPC which is a C
                  > implementation of OPC code available under LGPL, you can use it as
                  > examples... Start with a simple server, look at the OPC
                  > groups/items/browsing later...[/color]

                  I've already encountered LightOPC. Now, as its recommended here, I'll have a
                  look into it. Thanks!
                  [color=blue]
                  > Would be good to hear how you progress...[/color]

                  I'll keep this group informed, but it certainly will take its time until
                  then...

                  Many thanks and kind regards
                  Franz GEIGER



                    Comment

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