Creating GDS variables - Part 2

Now that we have seen how the PLCnext CLI can help us, let's use it to create a project containing an ACF component that creates some GDS variables.

  • Create a new project on the host system:

    $ plcncli new acfproject --name MyGdsProject --namespace MyNamespace --component MyComponent --verbose
  • Set the build target for the project:

    $ cd MyGdsProject
    $ plcncli set target --add --name AXCF2152 --version 2021.9

    If the target is ambiguous or cannot be found, you can use the following command to see the list of installed targets that the PLCnext CLI knows about:

    $ plcncli get targets
  • Edit the source code using your favourite editor. In this case we will use Visual Studio Code:

    $ code .

    You can see that the PLCnext CLI has created the following source and configuration files in the MyGdsProject directory:

    ├── CMakeLists.txt
    ├── external
    ├── How_to_deploy.txt
    ├── plcnext.proj
    └── src
        ├── MyComponent.cpp
        ├── MyComponent.hpp
        └── MyGdsProjectLibrary.acf.config
  • Add a GDS variable to the section indicated in the component .hpp file:

    Arp::uint8 MyGdsVariable;

    GDS variables are also referred to as "ports". The PLCnext Info Center provides detailed information on GDS port definitions in C++ code, including the attributes that can be applied to GDS ports defined in this way.

  • Change the .acf.config file if necessary, e.g. the path to the shared object library file.

  • Save the edited file(s)

  • On the command-line, use the PLCnext CLI to generate the intermediate files for the project:

    $ plcncli generate code --verbose

    You can see that the PLCnext CLI has now created a lot of files in the MyGdsProject directory, including the following:

    ├── intermediate
    │   └── code
    │       ├── MyComponent.meta.cpp
    │       ├── MyGdsProjectLibrary.cpp
    │       ├── MyGdsProjectLibrary.hpp
    │       └── MyGdsProjectLibrary.meta.cpp

    These C++ source files contain additional code required for the PLCnext runtime to create instances of the C++ component and its GDS port(s).

  • Build the project:

    $ plcncli build --verbose

    This command uses CMake to build the project for all the specified targets.

  • Deploy the shared object library and the .acf.config file to the PLC as you've done previously.

  • Restart the PLCnext Runtime.

Your ACF component instance now includes a GDS port in the Global Data Space that can be accessed by other components using the Data Access RSC service.