Calling External C Functions in a Function

In addition to functions written in Modelica, you can use external functions written in ANSI / ISO C.

For each external function, it is necessary to declare a Modelica interface. This declaration provides the required information needed to call the function from a Modelica model, and in some simple cases, provide argument conversion.

The following scenario describes a simple use case. For more about external C functions, see www.modelica.org and read the Modelica Specification.

This task shows you how to:

Before you begin: Open the Modelica Editor to edit Modelica text.
See Also
Displaying and Editing Modelica Text

Manage External C Function Files with Resources Management

You can use Resources Management when creating a function calling an external C function, in such a way that the solution can be distributed.

Note: To clarify the context, the example below includes building a simple library with a model using a function calling an external C function. The core however is the function.

  1. Create a library MyLib, version 1.0. See Creating a Modelica Library or Dymola Behavior Library.
  2. Create an empty model MyModel in MyLib. See Creating an Empty Class or Extending from an Existing Class.
  3. Create an empty function myFunction in MyLib. See Creating an Empty Class or Extending from an Existing Class.
  4. From the Behavior Authoring section of the action bar, click Resources Management .
  5. Add the external C function files in a suitable structure. See Managing External Resources.
    The pane part of the Resources Management window after inserting the resources looks like (both win32 and win64 files have been added for completeness):

  6. Click OK to validate and close the Resources Management window.
  7. These resources can now be referred to in the Modelica text of the function myFunction. Edit the Modelica text to (note the paths)


  8. The function can be used in MyModel. An example of the code of the model is:


  9. Save the library to the database.

Call an External C Function as Local Files

You can build a function that uses an external C function from local files on your computer, without adding them as resources.

Note: This solution is local on your computer.

  1. On your computer, position your external C function files where you want them, e. g.:




  2. From Me > Preferences > App Preferences > 3D Modeling > Systems Modeling and Execution > Dymola Behavior Modeling Me, the Compiler tab, enter the directory path of your files. See Compiler.


  3. In your Modelica text, enter your external C function:

    Note: The below also includes an example of a model using the function.