Diff: Biquad.hpp

Revision:

0:d2f279439aaf

Child:

1:69a8b728e8d2

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Biquad.hpp	Thu Sep 03 00:42:10 2015 +0000
@@ -0,0 +1,55 @@
+//----------------------------------------------------------------
+//  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
+//
+//      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
+//
+//  2015/09/02, Copyright (c) 2015 MIKAMI, Naoki
+//----------------------------------------------------------------
+
+#ifndef IIR_BIQUAD_HPP
+#define IIR_BIQUAD_HPP
+
+#include "mbed.h"
+
+namespace Mikami
+{
+    class Biquad
+    {
+    public:
+        struct Coefs { float a1, a2, b1, b2; };
+
+        Biquad() {}     // default constructor
+
+        Biquad(const Coefs ck)
+              : a1_(ck.a1), a2_(ck.a2), b1_(ck.b1), b2_(ck.b2)
+        { Clear(); }       
+
+        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_;   // coefficients
+        float un1_, un2_;           // buffer for delay
+
+        // disallow copy constructor and assignment operator
+        Biquad(const Biquad&);
+        Biquad& operator = (const Biquad&);
+    };
+}
+#endif  // IIR_BIQUAD_HPP
+