Diff: MyClasses_Functions/BiquadGrEq.hpp

Revision:

0:e953eb392151

diff -r 000000000000 -r e953eb392151 MyClasses_Functions/BiquadGrEq.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MyClasses_Functions/BiquadGrEq.hpp	Wed Apr 27 13:56:39 2016 +0000
@@ -0,0 +1,66 @@
+//--------------------------------------------------------------
+//  グラフィックイコライザで使う 1D タイプの 2 次のフィルタ
+//  Biquad filter of 1D type for graphic equalizer
+//      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] = b0*u[n] + b1*u[n-1] + b2*u[n-2]
+//          x[n] :  input signal
+//          y[n] :  output signal
+//
+// 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 BiquadGrEq
+    {
+    public:
+        struct Coefs { float a1, a2, b0, b1, b2; };
+
+        BiquadGrEq() {}     // Default constructore
+
+        BiquadGrEq(const Coefs ck)
+        {
+            SetCoefficients(ck);
+            Clear();
+        }
+        
+        void SetCoefficients(const Coefs ck)
+        {
+            a1_ = ck.a1;
+            a2_ = ck.a2;
+            b0_ = ck.b0;
+            b1_ = ck.b1;
+            b2_ = ck.b2;
+        }
+
+        float Execute(float xn)
+        {
+            float un = xn + a1_*un1_ + a2_*un2_;
+            float yn = b0_*un + b1_*un1_ + b2_*un2_;
+        
+            un2_ = un1_;
+            un1_ = un;
+
+            return yn;
+        }
+
+        void Clear() { un1_ = un2_ = 0; }
+
+    private:
+        float a1_, a2_, b0_, b1_, b2_;
+        float un1_, un2_;
+
+        // disallow copy constructor
+        BiquadGrEq(const BiquadGrEq&);
+    };
+}
+#endif  // IIR_BIQUAD_HPP
+