Real-Time Filters

Listing 1

//first_ord.h
#ifndef M_PI
#define M_PI   3.14159265358979323846
#endif

#include <math.h>
#define hpf 1.0
#define lpf -1.0
struct fstord {
    double  fc; //corner frequency
    double  fs; //sample rate
    double  alpha;  //analog frequency parameter
    double  acoef;  //a coefficient
    double  bcoef;  //b coefficient
    double  gain;   //filter gain
    double  xn_1;   //xn-1
    double  yn_1;   //yn-1
    double  type;   //hpf or lpf
};