不韋 呂 / F746_SD_VarableFilter

SD card player with variable cotoff frequency lowpass and highpass IIR filter. SD カードの *.wav ファイルのオーディオ信号を，遮断周波数可変 IIR 低域通過および高域通過フィルタを通して，ボードに搭載されているCODEC で出力する．このプログラムについては，CQ出版社インターフェース誌 2018年8月号で解説している．

Dependencies:   F746_GUI F746_SAI_IO FrequencyResponseDrawer SD_PlayerSkeleton

MyVariableFilter/IIR_CascadeFrqResp.hpp@11:399670d24ed9, 2017-04-10 (annotated)

Committer:
MikamiUitOpen
Date:
Mon Apr 10 01:44:22 2017 +0000
Revision:
11:399670d24ed9
Parent:
10:3532c05aa1a9 
12

Who changed what in which revision?

UserRevisionLine numberNew contents of line
MikamiUitOpen 0:92078e38d79f 1 //-----------------------------------------------------------
MikamiUitOpen 0:92078e38d79f 2 // Frequency response for IIR filter of cascade form
MikamiUitOpen 0:92078e38d79f 3 //
MikamiUitOpen 10:3532c05aa1a9 4 // 2017/03/28, Copyright (c) 2017 MIKAMI, Naoki
MikamiUitOpen 0:92078e38d79f 5 //-----------------------------------------------------------
MikamiUitOpen 0:92078e38d79f 6
MikamiUitOpen 0:92078e38d79f 7 #ifndef IIR_CASCADE_FREQUENCY_RESPONSE_HPP
MikamiUitOpen 0:92078e38d79f 8 #define IIR_CASCADE_FREQUENCY_RESPONSE_HPP
MikamiUitOpen 0:92078e38d79f 9
MikamiUitOpen 0:92078e38d79f 10 #include "FrequancyResponseBase.hpp"
MikamiUitOpen 0:92078e38d79f 11 #include "Biquad.hpp"
MikamiUitOpen 0:92078e38d79f 12
MikamiUitOpen 0:92078e38d79f 13 namespace Mikami
MikamiUitOpen 0:92078e38d79f 14 {
MikamiUitOpen 0:92078e38d79f 15 class IIR_CascadeFrqResp : public FrequencyResponse
MikamiUitOpen 0:92078e38d79f 16 {
MikamiUitOpen 0:92078e38d79f 17 public:
MikamiUitOpen 0:92078e38d79f 18 IIR_CascadeFrqResp() {}
MikamiUitOpen 0:92078e38d79f 19
MikamiUitOpen 0:92078e38d79f 20 // 次数とフィルタの係数設定
MikamiUitOpen 0:92078e38d79f 21 void SetParams(int order, float g0, Biquad::Coefs ck[])
MikamiUitOpen 0:92078e38d79f 22 {
MikamiUitOpen 0:92078e38d79f 23 order_ = order;
MikamiUitOpen 0:92078e38d79f 24 g0_ = g0;
MikamiUitOpen 0:92078e38d79f 25 ck_ = ck;
MikamiUitOpen 0:92078e38d79f 26 }
MikamiUitOpen 0:92078e38d79f 27
MikamiUitOpen 0:92078e38d79f 28 // 周波数応答の絶対値を返す関数, 引数: z^(-1)
MikamiUitOpen 0:92078e38d79f 29 virtual float AbsH_z(Complex u)
MikamiUitOpen 0:92078e38d79f 30 {
MikamiUitOpen 0:92078e38d79f 31 Complex h = g0_;
MikamiUitOpen 0:92078e38d79f 32 for (int k=0; k<order_/2; k++)
MikamiUitOpen 10:3532c05aa1a9 33 h = h*(1.0f + (ck_[k].b1 + ck_[k].b2*u)*u)
MikamiUitOpen 10:3532c05aa1a9 34 /(1.0f - (ck_[k].a1 + ck_[k].a2*u)*u);
MikamiUitOpen 0:92078e38d79f 35 return abs(h);
MikamiUitOpen 0:92078e38d79f 36 }
MikamiUitOpen 0:92078e38d79f 37
MikamiUitOpen 0:92078e38d79f 38 private:
MikamiUitOpen 0:92078e38d79f 39 int order_;
MikamiUitOpen 0:92078e38d79f 40 float g0_;
MikamiUitOpen 0:92078e38d79f 41 Biquad::Coefs *ck_;
MikamiUitOpen 0:92078e38d79f 42
MikamiUitOpen 0:92078e38d79f 43 // disallow copy constructor and assignment operator
MikamiUitOpen 0:92078e38d79f 44 IIR_CascadeFrqResp(const IIR_CascadeFrqResp&);
MikamiUitOpen 0:92078e38d79f 45 IIR_CascadeFrqResp& operator=(const IIR_CascadeFrqResp&);
MikamiUitOpen 0:92078e38d79f 46 };
MikamiUitOpen 0:92078e38d79f 47 }
MikamiUitOpen 0:92078e38d79f 48 #endif // IIR_CASCADE_FREQUENCY_RESPONSE_HPP