Diff: Biquad.hpp

Revision:

0:3d6eb7cd2ee1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Biquad.hpp	Thu Oct 23 00:37:00 2014 +0000
@@ -0,0 +1,44 @@
+//--------------------------------------------------------------
+// Biquad filter for IIR filter of cascade structure
+// 2014/10/21, Copyright (c) 2014 MIKAMI, Naoki
+//--------------------------------------------------------------
+
+#ifndef IIR_BIQUAD_HPP
+#define IIR_BIQUAD_HPP
+
+#include "mbed.h"
+
+// 2nd order IIR filter
+class Biquad
+{
+public:
+    struct Coefs { float a1, a2, b1, b2; };
+
+    Biquad() {}     // Default constructore
+
+    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_;
+    float un1_, un2_;
+
+    Biquad(const Biquad&);
+};
+
+#endif  // IIR_BIQUAD_HPP
+