MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Scaricare il pdf (Pagina 90)

3 Writing S-Functions As C-MEX files

3-46

the mdlZeroCrossings routine to return the nonsampled zero crossings. See

matlabroot/simulink/src/sfun_zc.c for an example.

mdlSetWorkWidths

The optional simulation only routine, mdlSetWorkWidths, is called after input

port width, output port width, and sample times of the S -function have been

determined to set any state- and work-vector sizes that are a function of the

input, output, and/or s ample times. T his routine is used to specify the nonzero

work vector widths via t he ma cros

ssNumContStates, ssSetNumDiscStates,

ssSetNumRWork, ssSetNumIWork, ssSetNumPWork, ssSetNumModes,and

ssSetNumNonsampledZCs.

An Example Involving a Pointer Work Vector

This exampl e opens a file and stores the FILE pointer in the pointer-work

vector.

Thestatementbelow,includedinthe

mdlInititalizeSizes function,indicates

that the pointer-work vector is to contain one element:

ssSetNumPWork(S, 1) /* pointer-work vector */

The code below uses the pointer-work vector to store a FILE pointer, returned

from the standard I/O function,

fopen:

#define MDL_START /* Change to #undef to remove function. */

#if defined(MDL_START)

static void mdlStart(real_T *x0, SimStruct *S)

{

FILE *fPtr;

void **PWork = ssGetPWork(S);

fPtr = fopen("file.data", "r");

PWork[0] = fPtr;

}

#endif /* MDL_START */

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guida Utente Pagina 90