Giving additional resource(.so file) to an s-function and generate FMU

I am generating FMU from a matlab s-function. The s-function needs an additional resource (.so file) to run and this is made available in the current path. No reference or definition given in s-function for this additional resource( I don't know how to give)

Issue: The FMU runs only when the additional resource (.so file) is in the current path else Matlab crashes. I want to run the FMU by having this additional resouce (.so file) inside FMU so that it can run on another PC. I tried creating a "resources/filename.so" inside MyModel.fmu unfortunately it doesn't helps.

Any thoughts?

[Meg Noah]

Did you try 'addpath' to add the path of the .so file?

[Mayur]

Thanks @Meg Noah for your suggestion.

Yes. It works for running the sfunction. After that I am generating FMU and it fails to find the file while running the FMU. Also, manually copying the file inside FMU doesn't help

Answer 1

[Arushi]

Hi Mayur,

If your S-function depends on a .so file and you're trying to generate a portable FMU that works across different machines, here's what worked best for me:

• Include the .so file in the resources/ folder when exporting the FMU.
• Modify your S-function C/C++ code to dynamically load the .so using dlopen() with the full path.

void* handle = dlopen("myLibrary.so", RTLD_NOW);

• At runtime, the FMU is automatically extracted to a temporary directory. You can build the path to the .so file like this:

char path[PATH_MAX];
sprintf(path, "%s/resources/myLibrary.so", modelResourcePath);
void* handle = dlopen(path, RTLD_NOW);

modelResourcePath can be obtained from the FMU runtime or passed in using the FMI callback functions, depending on your setup.

This approach makes the FMU completely self-contained and portable.

Hope this helps!

[Mayur]

Hi,

Thank you @Arushi for your valuable input. I have modified the sfunction. But unfortunately I have few questions:

During the first test, I want to run the FMU in a simulink environment only. For this comment "modelResourcePath can be obtained from the FMU runtime or passed in using the FMI callback functions". How to define a modelResourcePath in sfunction?

"Include the .so file in the resources/ folder when exporting the FMU"

I am wondering how this step can be achieved before creating FMU? Since I am using Matlab 2021a with FMI 2.0. It doesn't have the the ability to add resources. After the FMU is created I unzip it and manually add to to anew resource folder.

[Arushi]

Hi Mayur,

Since you’re on MATLAB R2021b, you can use the built-in Additional Files option when exporting the FMU to include your .so dependency directly inside the FMU package. This removes the need to unzip/re-zip the FMU manually.

Export Simulink Model to Standalone FMU

In the “Additional Files” section of the export dialog, you can specify:

• binaries/<arch>/ for dependent libraries loaded automatically by the FMU binary, or
• resources/ for files you plan to load manually (e.g. dlopen in your S-Function).

Once you add your .so here and adjust your S-Function to build the absolute path at runtime, your FMU should run without needing the .so in the working directory.

[Mayur]

Hi,

The 2021b version has a limitation to add additonal resources.

See limitatiion section: https://www.mathworks.com/help/releases/R2021b/slcompiler/gs/export-simulink-models-to-functional-mock-up-units.html

Also, check this dialog box in the attached image.