Version 2.0.2. Patch for issue 92/93

Author: kosme

library.json

@@ -25,7 +25,7 @@
       "email": "bim.overbohm@googlemail.com"
     }
   ],
-  "version": "2.0.1",
+  "version": "2.0.2",
   "frameworks": ["arduino","mbed","espidf"],
   "platforms": "*",
   "headers": "arduinoFFT.h"

library.properties

@@ -1,9 +1,9 @@
 name=arduinoFFT
-version=2.0.1
+version=2.0.2
 author=Enrique Condes <enrique@shapeoko.com>
 maintainer=Enrique Condes <enrique@shapeoko.com>
-sentence=A library for implementing floating point Fast Fourier Transform calculations on Arduino.
-paragraph=With this library you can calculate the frequency of a sampled signal.
+sentence=A library for implementing floating point Fast Fourier Transform calculations on the Arduino framework.
+paragraph=With this library you can calculate the dominant frequency of a sampled signal.
 category=Data Processing
 url=https://github.com/kosme/arduinoFFT
 architectures=*

src/arduinoFFT.cpp

@@ -40,7 +40,7 @@ ArduinoFFT<T>::ArduinoFFT(T *vReal, T *vImag, uint_fast16_t samples,
 template <typename T> ArduinoFFT<T>::~ArduinoFFT(void) {
   // Destructor
   if (_precompiledWindowingFactors) {
-    delete [] _precompiledWindowingFactors;
+    delete[] _precompiledWindowingFactors;
   }
 }
 
@@ -142,6 +142,10 @@ void ArduinoFFT<T>::compute(T *vReal, T *vImag, uint_fast16_t samples,
 #endif
     }
   }
+  // The computation result at position 0 should be as close to 0 as possible.
+  // The DC offset on the signal produces a spike on position 0 that should be
+  // eliminated to avoid issues.
+  vReal[0] = 0;
 }
 
 template <typename T> void ArduinoFFT<T>::dcRemoval(void) const {
@@ -247,7 +251,7 @@ void ArduinoFFT<T>::majorPeakParabola(T *vData, uint_fast16_t samples,
 
     // And magnitude is at the extrema of the parabola if you want It...
     if (magnitude != nullptr) {
-      *magnitude = a * x * x + b * x + c;
+      *magnitude = (a * x * x) + (b * x) + c;
     }
 
     // Convert to frequency
@@ -270,7 +274,7 @@ void ArduinoFFT<T>::setArrays(T *vReal, T *vImag, uint_fast16_t samples) {
     _oneOverSamples = 1.0 / samples;
 #endif
     if (_precompiledWindowingFactors) {
-      delete [] _precompiledWindowingFactors;
+      delete[] _precompiledWindowingFactors;
     }
     _precompiledWindowingFactors = new T[samples / 2];
   }
@@ -501,7 +505,7 @@ template <typename T> double ArduinoFFT<T>::sqrt_internal(double x) const {
 #endif
 
 template <typename T>
-const T ArduinoFFT<T>::_WindowCompensationFactors[10] = {
+const T ArduinoFFT<T>::_WindowCompensationFactors[11] = {
     1.0000000000 * 2.0, // rectangle (Box car)
     1.8549343278 * 2.0, // hamming
     1.8554726898 * 2.0, // hann
@@ -511,7 +515,10 @@ const T ArduinoFFT<T>::_WindowCompensationFactors[10] = {
     2.7557840395 * 2.0, // blackman nuttall
     2.7929062517 * 2.0, // blackman harris
     3.5659039231 * 2.0, // flat top
-    1.5029392863 * 2.0  // welch
+    1.5029392863 * 2.0, // welch
+    // This is added as a precaution, since this index should never be
+    // accessed under normal conditions
+    1.0 // Custom, precompiled value.
 };
 
 template class ArduinoFFT<double>;

src/arduinoFFT.h

@@ -41,6 +41,7 @@
 #include <math.h>
 #include <stdint.h>
 #endif
+#include "enumsFFT.h"
 
 // This definition uses a low-precision square root approximation instead of the
 // regular sqrt() call
@@ -52,46 +53,7 @@
   #endif
 #endif
 
-enum class FFTDirection { Forward, Reverse };
-
-enum class FFTWindow {
-  Rectangle,        // rectangle (Box car)
-  Hamming,          // hamming
-  Hann,             // hann
-  Triangle,         // triangle (Bartlett)
-  Nuttall,          // nuttall
-  Blackman,         // blackman
-  Blackman_Nuttall, // blackman nuttall
-  Blackman_Harris,  // blackman harris
-  Flat_top,         // flat top
-  Welch,            // welch
-  Precompiled       // Placeholder for using custom or precompiled window values
-};
 #define FFT_LIB_REV 0x20
-/* Custom constants */
-/* These defines keep compatibility with pre 2.0 code */
-#define FFT_FORWARD FFTDirection::Forward
-#define FFT_REVERSE FFTDirection::Reverse
-
-/* Windowing type */
-#define FFT_WIN_TYP_RECTANGLE FFTWindow::Rectangle /* rectangle (Box car) */
-#define FFT_WIN_TYP_HAMMING FFTWindow::Hamming     /* hamming */
-#define FFT_WIN_TYP_HANN FFTWindow::Hann           /* hann */
-#define FFT_WIN_TYP_TRIANGLE FFTWindow::Triangle   /* triangle (Bartlett) */
-#define FFT_WIN_TYP_NUTTALL FFTWindow::Nuttall     /* nuttall */
-#define FFT_WIN_TYP_BLACKMAN FFTWindow::Blackman   /* blackman */
-#define FFT_WIN_TYP_BLACKMAN_NUTTALL                                           \
-  FFTWindow::Blackman_Nuttall /* blackman nuttall */
-#define FFT_WIN_TYP_BLACKMAN_HARRIS                                            \
-  FFTWindow::Blackman_Harris                    /* blackman harris*/
-#define FFT_WIN_TYP_FLT_TOP FFTWindow::Flat_top /* flat top */
-#define FFT_WIN_TYP_WELCH FFTWindow::Welch      /* welch */
-/* End of compatibility defines */
-
-/* Mathematial constants */
-#define twoPi 6.28318531
-#define fourPi 12.56637061
-#define sixPi 18.84955593
 
 template <typename T> class ArduinoFFT {
 public:
@@ -138,14 +100,14 @@ template <typename T> class ArduinoFFT {
 
 private:
   /* Variables */
-  static const T _WindowCompensationFactors[10];
+  static const T _WindowCompensationFactors[11];
 #ifdef FFT_SPEED_OVER_PRECISION
   T _oneOverSamples = 0.0;
 #endif
   bool _isPrecompiled = false;
   bool _precompiledWithCompensation = false;
   uint_fast8_t _power = 0;
-  T *_precompiledWindowingFactors;
+  T *_precompiledWindowingFactors = nullptr;
   uint_fast16_t _samples;
   T _samplingFrequency;
   T *_vImag;

src/enumsFFT.h

@@ -0,0 +1,43 @@
+#ifndef enumsFFT_h
+#define enumsFFT_h
+/* Custom constants */
+/* These defines keep compatibility with pre 2.0 code */
+#define FFT_FORWARD FFTDirection::Forward
+#define FFT_REVERSE FFTDirection::Reverse
+
+/* Windowing type */
+#define FFT_WIN_TYP_RECTANGLE FFTWindow::Rectangle /* rectangle (Box car) */
+#define FFT_WIN_TYP_HAMMING FFTWindow::Hamming     /* hamming */
+#define FFT_WIN_TYP_HANN FFTWindow::Hann           /* hann */
+#define FFT_WIN_TYP_TRIANGLE FFTWindow::Triangle   /* triangle (Bartlett) */
+#define FFT_WIN_TYP_NUTTALL FFTWindow::Nuttall     /* nuttall */
+#define FFT_WIN_TYP_BLACKMAN FFTWindow::Blackman   /* blackman */
+#define FFT_WIN_TYP_BLACKMAN_NUTTALL                                           \
+  FFTWindow::Blackman_Nuttall /* blackman nuttall */
+#define FFT_WIN_TYP_BLACKMAN_HARRIS                                            \
+  FFTWindow::Blackman_Harris                    /* blackman harris*/
+#define FFT_WIN_TYP_FLT_TOP FFTWindow::Flat_top /* flat top */
+#define FFT_WIN_TYP_WELCH FFTWindow::Welch      /* welch */
+/* End of compatibility defines */
+
+/* Mathematial constants */
+#define twoPi 6.28318531
+#define fourPi 12.56637061
+#define sixPi 18.84955593
+
+enum class FFTWindow {
+  Rectangle,        // rectangle (Box car)
+  Hamming,          // hamming
+  Hann,             // hann
+  Triangle,         // triangle (Bartlett)
+  Nuttall,          // nuttall
+  Blackman,         // blackman
+  Blackman_Nuttall, // blackman nuttall
+  Blackman_Harris,  // blackman harris
+  Flat_top,         // flat top
+  Welch,            // welch
+  Precompiled       // Placeholder for using custom or precompiled window values
+};
+
+enum class FFTDirection { Forward, Reverse };
+#endif