lpf.h

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#ifndef LIBA_LPF_H
#define LIBA_LPF_H
 
#include "math.h"


typedef struct a_lpf
{
    a_real alpha; 
    a_real output; 
#if defined(__cplusplus)
    A_INLINE void gen(a_real fc, a_real ts)
    {
        alpha = ts / (A_REAL_1_TAU / fc + ts);
    }
    A_INLINE a_real operator()(a_real x)
    {
        output += (x - output) * alpha;
        return output;
    }
    A_INLINE void zero() { output = 0; }
#endif /* __cplusplus */
} a_lpf;
#if defined(__cplusplus)
namespace a
{
typedef struct a_lpf lpf;
} /* namespace a */
#endif /* __cplusplus */
/* clang-format off */
#define A_LPF_1(alpha) {a_real_c(alpha), 0}
#define A_LPF_2(fc, ts) {A_LPF_GEN(fc, ts), 0}
/* clang-format on */
#define A_LPF_GEN(fc, ts) (a_real_c(ts) / (A_REAL_1_TAU / a_real_c(fc) + a_real_c(ts)))

A_INTERN a_real a_lpf_gen(a_real fc, a_real ts)
{
    return ts / (A_REAL_1_TAU / fc + ts);
}

A_INTERN void a_lpf_init(a_lpf *ctx, a_real alpha)
{
    ctx->alpha = alpha;
    ctx->output = 0;
}

A_INTERN a_real a_lpf_iter(a_lpf *ctx, a_real x)
{
    ctx->output += (x - ctx->output) * ctx->alpha;
    return ctx->output;
}

A_INTERN void a_lpf_zero(a_lpf *ctx) { ctx->output = 0; }

 
#endif /* a/lpf.h */