Diff: QuadOscIirFixed.hpp

Revision:

0:97d46bd73383

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/QuadOscIirFixed.hpp	Wed Aug 02 11:50:17 2017 +0000
@@ -0,0 +1,38 @@
+//--------------------------------------------------------------
+//  IIR フィルタを利用する二相発振器のクラス
+//
+//  2017/03/02, Copyright (c) 2017 MIKAMI, Naoki
+//--------------------------------------------------------------
+
+#include "mbed.h"
+#include "FixedFloat.hpp"
+
+#ifndef QUAD_PHASE_OSC_IIR_FIXED_HPP
+#define QUAD_PHASE_OSC_IIR_FIXED_HPP
+
+class QuadOscIIR
+{
+public:
+    // Constructor
+    QuadOscIIR(float f0, float ts)
+        : A1_(ToFixed14(2.0f*cosf(6.283185f*f0*ts*1.0E-6f))),
+          B1S_(ToFixed14(sinf(6.283185f*f0*ts*1.0E-6f))),
+          B1C_(ToFixed14(-cosf(6.283185f*f0*ts*1.0E-6f))),
+          un1_(ToFixed14(1.0f)), un2_(0) {}
+    
+    void Generate(int16_t &sinX, int16_t &cosX)
+    {
+        // u[n] = a1*u[n-1] - u[n-2]
+        int32_t un = Round14(A1_*un1_) - un2_;
+
+        sinX = Round14(B1S_*un1_);
+        cosX = un + Round14(B1C_*un1_);
+
+        un2_ = un1_;    // u[n-2] ← u[n-1]
+        un1_ = un;      // u[n-1] ← u[n]
+    }
+private:
+    const int16_t A1_, B1S_, B1C_;
+    int32_t un1_, un2_;
+};
+#endif  // QUAD_PHASE_OSC_IIR_FIXED_HPP