RM0020 datasheet(46/69 Pages) STMICROELECTRONICS

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Function API

RM0020

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#ifdef __ghs__

#pragma alignvar (4)

#endif

ALIGN_DCC(4)

short x[288/*+2*/] ALIGN_MWERKS(4); /* +2 to ensure there are 4

bytes of readable memory behind x */

#ifdef __ghs__

#pragma alignvar (4)

#endif

ALIGN_DCC(4)

short y[256] ALIGN_MWERKS(4);

short hr[33/*+1*/] = { /* +1 to ensure there are 2 bytes of readable

memory behind hr */

-50,-62,-82,-103,-111,-

84,0,163,418,767,1196,1676,2167,2621,2988,3227,3310,3227,2988,2621,

2167,1676,1196,767,418,163,0,-84,-111,-103,-82,-62,-50,

};

unsigned short N, ntaps;

void main(void)

{

/* filter the samples in x with FIR filter of 32nd order, */

/* write result into y, hr are filter coefficients stored */

/* in reversed order */

N = 256;

ntaps = 33;

fir_frac16(N, ntaps, x, y, hr);

}

6.24

iir_float_1st - float first-order IIR filter

Function call:

void iir_float_1st (unsigned short N, float *x, float *y, float *c,

float *s);

Arguments:

Table 24.

iir_float_1st arguments(1)

The arrays x,y,s must be double-word aligned, the array c must be word aligned (implicit alignment

of float data). There must be 16 bytes of readable memory behind the array x. There are returned

new values of x(-1), y(-1) in the array s to be ready for next function call.

Nin

number of input and output samples (N must be multiple of 4, must be

>= 8)

array of input samples of length N, x(0) x(1) ... x(N-1)

out

array of output samples of length N, y(0) y(1) ... y(N-1)

array of filter coefficients, c[3] = {b0, b1, a1}

in/out

array of previous input and output values (state vector), s[2] = {x(-1),

y(-1)}

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