MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Scaricare il pdf (Pagina 177)

Writing Wrapper S-Functions

4-11

Using an S-function wrapper to import algorithms in your Simulink model

means that the S-function serves as an interface that calls your C code

algorithmsfrom

mdlOutputs.S-functionwrappershavetheadvantagethatyou

can quickly integrate large stand-alone C code into your model without having

to make changes to the code.

This is an example of a model that includes an S-function wrapper.

Figure 4-1: An Example Model That Includes an S-Function Wrapper

There are two files asso ciatedwithwrapsfcn blo c k, the S-function wrapperan d

the C code that contains the algorithm. This is the S -function wrapper code for

this example, called

wrapsfcn.c:

#define S_FUNCTION_NAME wrapsfcn

#define S_FUNCTION_LEVEL 2

#include “simstruc.h”

extern real_T my_alg(real_T u);

* mdlInitializeSizes - initialize the sizes array

static void mdlInitializeSizes(SimStruct *S)

{

ssSetNumSFcnParams( S, 0); /*number of input arguments*/

if (!ssSetNumInputPorts(S, 1)) return;

ssSetInputPortWidth(S, 0, 1);

ssSetInputPortDirectFeedThrough(S, 0, 1);

if (!ssSetNumOutputPorts(S,1)) return;

ssSetOutputPortWidth(S, 0, 1);

ssSetNumSampleTimes( S, 1);

}

Declare my_alg as

extern.

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Pagina 177