Creating External Models (Control Design and Simulation Module)

Third parties can use the External Model Interface (EMI) to create an external, or third-party, model in C/C++. Refer to the Example 1: Creating an External Model topic for an example of a C/C++ project that defines an external model.

Complete the following steps to create an external model.

1. Create a C/C++ project that uses the External Model Interface functions to define the dynamic equations for the external model you want to simulate. Use the following guidelines when creating the C/C++ project:
   • Use C-style calling conventions when defining the Callbacks functions.
   • Use the EMI_GetCurrentVersion function in the Simulation shared library NILVSim.dll, (macOS) NILVSim.framework or (Linux) NILVSim.so, located in the labview/vi.lib/Simulation/Implementation/Shared/ directory, to determine which version of the External Model Interface is installed. Generate C/C++ code that is compatible with the installed version of the External Model Interface.
   • Include the SIM_EMI_API.h header file, located in the labview\CCodeGen\Simulation directory. This header file includes definitions and declarations for all functions and data types that the EMI supports.
   • Export the EMI_CB_ModelInterface function. You must export the EMI_CB_ModelInterface function for each model you create.
   • Export Callbacks functions as appropriate for the structure of the model. For example, if the model contains indirect outputs, you must export the EMI_CB_CalculateIndirectOutputs function to calculate the indirect outputs. If you do not export the appropriate Callbacks functions, LabVIEW returns an error when you attempt to simulate the model.
   • Ensure the model has no more than 25 total inputs, outputs, and parameters.
2. Build the C/C++ project into a (Windows) .dll, (macOS) .framework or .dylib, or (Linux) .so shared library file.
3. Distribute the shared library to end users.

LabVIEW users can use EMI to simulate the external model in the LabVIEW Control Design and Simulation Module.