Output the audio signal (*.bin) with filtering by IIR filter in the SD card using onboard CODEC. For *.wav file, F746_SD_WavPlayer and F746_SD_GraphicEqualiser are published on mbed. SD カードのオーディオ信号 (*.bin) を遮断周波数可変の IIR フィルタを通して,ボードに搭載されているCODEC で出力する.*.wav 形式のファイル用には,F746_SD_WavPlayer と F746_SD_GraphicEqualiser を mbed で公開している.
Dependencies: BSP_DISCO_F746NG_patch_fixed F746_GUI LCD_DISCO_F746NG SDFileSystem_Warning_Fixed TS_DISCO_F746NG mbed
Diff: MyClasses_Functions/Biquad.hpp
- Revision:
- 0:6748e3332e85
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/MyClasses_Functions/Biquad.hpp Fri Apr 08 13:11:53 2016 +0000 @@ -0,0 +1,65 @@ +//-------------------------------------------------------------- +// 縦続形 IIR フィルタで使う 1D タイプの 2 次のフィルタ +// Biquad filter of 1D type for IIR filter of cascade structure +// このクラスでは,係数は実行中に書き換えられることを想定している +// +// u[n] = x[n] + a1*u[n-1] + a2*u[n-2] +// y[n] = u[n] + b1*u[n-1] + b2*u[n-2] +// x[n] : input signal +// y[n] : output signal +// b0 = 1 +// +// 2016/03/25, Copyright (c) 2016 MIKAMI, Naoki +//-------------------------------------------------------------- + +#ifndef IIR_BIQUAD_HPP +#define IIR_BIQUAD_HPP + +#include "mbed.h" + +// 2nd order IIR filter +namespace Mikami +{ + class Biquad + { + public: + struct Coefs { float a1, a2, b1, b2; }; + + Biquad() {} // Default constructore + + Biquad(const Coefs ck) + { + SetCoefficients(ck); + Clear(); + } + + void SetCoefficients(const Coefs ck) + { + a1_ = ck.a1; + a2_ = ck.a2; + b1_ = ck.b1; + b2_ = ck.b2; + } + + float Execute(float xn) + { + float un = xn + a1_*un1_ + a2_*un2_; + float yn = un + b1_*un1_ + b2_*un2_; + + un2_ = un1_; + un1_ = un; + + return yn; + } + + void Clear() { un1_ = un2_ = 0; } + + private: + float a1_, a2_, b1_, b2_; + float un1_, un2_; + + // disallow copy constructor + Biquad(const Biquad&); + }; +} +#endif // IIR_BIQUAD_HPP