boting ren / Mbed 2 deprecated F746_SD_GraphicEqualizer_ren0620

revised version of F746_SD_GraphicEqualizer

Dependencies:   BSP_DISCO_F746NG F746_GUI F746_SAI_IO FrequencyResponseDrawer LCD_DISCO_F746NG SDFileSystem_Warning_Fixed TS_DISCO_F746NG mbed

Fork of F746_SD_GraphicEqualizer by 不韋 呂

MyClasses_Functions/GrEqParamsCalculator.hpp

Committer:
MikamiUitOpen
Date:
2016-04-27
Revision:
0:e953eb392151

File content as of revision 0:e953eb392151:

//------------------------------------------------------------------------------
//  Parameters calculator class of buquad unit for graphic equalizer
//  グラフィックイコライザで使う biquad フィルタの係数を計算するクラス
//
//   2016/04/27, Copyright (c) 2016 MIKAMI, Naoki
//------------------------------------------------------------------------------

#ifndef GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP
#define GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP

#include "mbed.h"
#include "BiquadGrEq.hpp"

namespace Mikami
{
    class GrEqParamsCalculator
    {
    public:
        // Constructor
        GrEqParamsCalculator(float fs) : FS_(fs) {}

        // 係数を計算する
        BiquadGrEq::Coefs Execute(float f0, float gDb, float qVal)
        {
            const float PI = 3.1415926536f;
            BiquadGrEq::Coefs coefs;
            
            float g_sqrt = sqrtf(powf(10, gDb/20.0f));
            float w0 = 2.0f*PI*f0/FS_;
            float alpha = sinf(w0)/(2.0f*qVal);
            float a0 = 1.0f + alpha/g_sqrt;
            coefs.a1 = 2.0f*cosf(w0)/a0;
            coefs.a2 = -(1.0f - alpha/g_sqrt)/a0;
            coefs.b0 = (1.0f + alpha*g_sqrt)/a0;
            coefs.b1 = -coefs.a1;
            coefs.b2 = (1.0f - alpha*g_sqrt)/a0;
            return coefs;
        }

    private:
        const float FS_;
    };
}
#endif  // GRAPHIC_EQALIZER_PARAMETER_CALCULATOR_HPP