User`s guide

Examples of C MEX-File S-Function Blocks
3-91
/*
* The continuous system is evaluated using a controllable state space
* representation of the transfer function. This implies that the
* output of the system is equal to:
*
* y(t) = Cx(t) + Du(t)
* = [ b1 b2 ... bn]x(t) + b0u(t)
*
* where b0, b1, b2, ... are the coefficients of the numerator
* polynomial:
*
* B(s) = b0 s^n + b1 s^n-1 + b2 s^n-2 + ... + bn-1 s + bn
*/
*y = *num++ * (*uPtrs[0]);
for (i = 0; i < nContStates; i++) {
*y += *num++ * *x++;
}
}
} /* end mdlOutputs */
#define MDL_UPDATE
/* Function: mdlUpdate ========================================================
* Abstract:
* Every time through the simulation loop, update the
* transfer function coefficients. Here we update the oldest bank.
*/
static void mdlUpdate(SimStruct *S, int_T tid)
{
if (ssIsSampleHit(S, 1, tid)) {
int_T i;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
int_T uIdx = 1;/*1st coeff is after signal input*/
int_T nContStates = ssGetNumContStates(S);
int_T nCoeffs = nContStates + 1;
int_T bankToUpdate = !ssGetIWork(S)[0];
real_T *num = ssGetRWork(S)+bankToUpdate*2*nCoeffs;
real_T *den = num + nCoeffs;
real_T den0;
int_T allZero;
/*
* Get the first denominator coefficient. It will be used
* for normalizing the numerator and denominator coefficients.
*
* If all inputs are zero, we probably could have unconnected
* inputs, so use the parameter as the first denominator coefficient.
*/
den0 = *uPtrs[uIdx+nCoeffs];