不韋 呂
CQ出版社インターフェース誌の2017年10月号で解説している二相発振器のプログラム
Diff: QuadOscIirFixed.hpp
- Revision:
- 0:97d46bd73383
diff -r 000000000000 -r 97d46bd73383 QuadOscIirFixed.hpp
--- /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