不韋 呂
Output the audio signal with filtering by IIR filter in the *.wav file on the SD card using onboard CODEC. 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．
Dependencies: BSP_DISCO_F746NG F746_GUI LCD_DISCO_F746NG SDFileSystem_Warning_Fixed TS_DISCO_F746NG mbed FrequencyResponseDrawer F746_SAI_IO Array_Matrix
Diff: MyClasses_Functions/Biquad.hpp
- Revision:
- 0:04b43b777fae
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MyClasses_Functions/Biquad.hpp Tue Apr 19 09:46:11 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