Motorola DSP Developer's Kit

Simulink S-Function MEX-Files

Before continuing, we recommend you read "Getting Started" (Chapter 1), "Creating a Model" (Chapter 3) and the "Writing S-Functions as C MEX-Files" section of "S-Functions" (Chapter 8), in Using Simulink. For more detailed information, refer to Writing S-Functions.

Note    The supplied Simulink files use macros defined in <matlab>/toolbox/motdsp/motdspmex/include/headers/56k/motdsp_api.h in place of the C++ style function calls. The purpose of these macros is to use the correct simulator object for each iteration (sample) of the simulation when in INTERACTIVE mode. If a sample hit occurs, as specified from the dialog box parameter, the simulator object will launch the simulator GUI. At other times, it will run in NON_INTERACTIVE mode. For a list of these macros see Macros.

Required Definitions

Define only the following macros in your MEX-file:

• S_MEX_FUNC_NAME
• S_FUNCTION_NAME

For the Simulink environment, these names must exactly match the name of the MEX-file source (including case sensitivity), omitting the .cpp extension. The functions supplied in the Motorola DSP Blockset (<matlab>/toolbox/motdsp/motdspmex/56300 and <matlab>/toolbox/motdsp/motdspmex/56600) are all prefixed with mot563_ or mot566_. Also, the S_MEX_FUNC_NAME macro is always defined as a string.

• S_FUNCTION_LEVEL

These macros are required for any MEX S-function. The S_FUNCTION_LEVEL macro is always defined to equal 2.

For example,

//fn name as a string.
#define S_MEX_FUNC_NAME  "motdsp_stemplate" 
//fn name for compile purposes.
#define S_FUNCTION_NAME  motdsp_stemplate
#define S_FUNCTION_LEVEL 2

The MAX*/MIN* macros described for MATLAB MEX-files are specifically not required for Simulink S-functions.

Also, the template provides an example of optional dialog box parameter checking within the mdlCheckParameters function.

/* Get the first dialog box parameter and 
   check to see if it is a string.*/
if (!mxIsChar(ssGetSFcnParam(S,0)) ) 
    {
    ssSetErrorStatus(S,"1st parameter to S-function must be a "
                    "string which represents the filename "
                    "of the command file.");
    return;
}

Terminating and Allocated Memory Cleanup

Input Objects