Fix bug on synthetic data generation

Examples/FFT_01/FFT_01.ino

@@ -60,11 +60,11 @@ void setup()
 void loop()
 {
   /* Build raw data */
-  double cycles = (((samples-1) * signalFrequency) / samplingFrequency); //Number of signal cycles that the sampling will read
+  double ratio = twoPi * signalFrequency / samplingFrequency; // Fraction of a complete cycle stored at each sample (in radians)
   for (uint16_t i = 0; i < samples; i++)
   {
-    vReal[i] = int8_t((amplitude * (sin((i * (twoPi * cycles)) / samples))) / 2.0);/* Build data with positive and negative values*/
-    //vReal[i] = uint8_t((amplitude * (sin((i * (twoPi * cycles)) / samples) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
+    vReal[i] = int8_t(amplitude * sin(i * ratio) / 2.0);/* Build data with positive and negative values*/
+    //vReal[i] = uint8_t((amplitude * (sin(i * ratio) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
     vImag[i] = 0.0; //Imaginary part must be zeroed in case of looping to avoid wrong calculations and overflows
   }
 

Examples/FFT_02/FFT_02.ino

@@ -63,10 +63,10 @@ void loop()
   for(double frequency = startFrequency; frequency<=stopFrequency; frequency+=step_size)
   {
     /* Build raw data */
-    double cycles = (((samples-1) * frequency) / sampling);
+    double ratio = twoPi * frequency / sampling; // Fraction of a complete cycle stored at each sample (in radians)
     for (uint16_t i = 0; i < samples; i++)
     {
-      vReal[i] = int8_t((amplitude * (sin((i * (twoPi * cycles)) / samples))) / 2.0);
+      vReal[i] = int8_t(amplitude * sin(i * ratio) / 2.0);/* Build data with positive and negative values*/
       vImag[i] = 0; //Reset the imaginary values vector for each new frequency
     }
     /*Serial.println("Data:");

Examples/FFT_04/FFT_04.ino

@@ -61,11 +61,11 @@ void setup()
 void loop()
 {
   /* Build raw data */
-  double cycles = (((samples-1) * signalFrequency) / samplingFrequency); //Number of signal cycles that the sampling will read
+  double ratio = twoPi * signalFrequency / samplingFrequency; // Fraction of a complete cycle stored at each sample (in radians)
   for (uint16_t i = 0; i < samples; i++)
   {
-    vReal[i] = int8_t((amplitude * (sin((i * (twoPi * cycles)) / samples))) / 2.0);/* Build data with positive and negative values*/
-    //vReal[i] = uint8_t((amplitude * (sin((i * (twoPi * cycles)) / samples) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
+    vReal[i] = int8_t(amplitude * sin(i * ratio) / 2.0);/* Build data with positive and negative values*/
+    //vReal[i] = uint8_t((amplitude * (sin(i * ratio) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
     vImag[i] = 0.0; //Imaginary part must be zeroed in case of looping to avoid wrong calculations and overflows
   }
   FFT = arduinoFFT(vReal, vImag, samples, samplingFrequency); /* Create FFT object */

Examples/FFT_05/FFT_05.ino

@@ -61,11 +61,11 @@ void setup()
 void loop()
 {
   /* Build raw data */
-  double cycles = (((samples-1) * signalFrequency) / samplingFrequency); //Number of signal cycles that the sampling will read
+  double ratio = twoPi * signalFrequency / samplingFrequency; // Fraction of a complete cycle stored at each sample (in radians)
   for (uint16_t i = 0; i < samples; i++)
   {
-    vReal[i] = int8_t((amplitude * (sin((i * (twoPi * cycles)) / samples))) / 2.0);/* Build data with positive and negative values*/
-    //vReal[i] = uint8_t((amplitude * (sin((i * (twoPi * cycles)) / samples) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
+    vReal[i] = int8_t(amplitude * sin(i * ratio) / 2.0);/* Build data with positive and negative values*/
+    //vReal[i] = uint8_t((amplitude * (sin(i * ratio) + 1.0)) / 2.0);/* Build data displaced on the Y axis to include only positive values*/
     vImag[i] = 0.0; //Imaginary part must be zeroed in case of looping to avoid wrong calculations and overflows
   }
   FFT = arduinoFFT(vReal, vImag, samples, samplingFrequency); /* Create FFT object */

README.md

@@ -58,7 +58,7 @@ Destructor
 * **!Compute**(double *vReal, double *vImag, uint16_t samples, uint8_t dir);
 * **!Compute**(double *vReal, double *vImag, uint16_t samples, uint8_t power, uint8_t dir);
 * **Compute**(uint8_t dir);
-Calcuates the Fast Fourier Transform.
+Calculates the Fast Fourier Transform.
 * **!DCRemoval**(double *vData, uint16_t samples);
 * **DCRemoval**();
 Removes the DC component from the sample data.

changeLog.txt

@@ -1,3 +1,9 @@
+28/12/23 v1.6.2
+Fix issue 52 and symplify calculation of synthetic data for examples 1, 2, 4, and 5.
+
+25/07/23 v1.6.1
+Code optimization for speed improvements. See issue 84 for more details.
+
 03/09/23 v1.6
 Include some functionality from development branch.
 

library.json

@@ -20,7 +20,7 @@
       "email": "[email protected]"
     }
   ],
-  "version": "1.6.1",
+  "version": "1.6.2",
   "frameworks": ["arduino","mbed","espidf"],
   "platforms": "*",
   "headers": "arduinoFFT.h"

library.properties

@@ -1,5 +1,5 @@
 name=arduinoFFT
-version=1.6.1
+version=1.6.2
 author=Enrique Condes <[email protected]>
 maintainer=Enrique Condes <[email protected]>
 sentence=A library for implementing floating point Fast Fourier Transform calculations on Arduino.

src/arduinoFFT.cpp

@@ -292,7 +292,7 @@ void arduinoFFT::Windowing(FFTWindow windowType, FFTDirection dir) {
 void arduinoFFT::Windowing(double *vData, uint16_t samples,
                            FFTWindow windowType, FFTDirection dir) {
 // Weighing factors are computed once before multiple use of FFT
-// The weighing function is symetric; half the weighs are recorded
+// The weighing function is symmetric; half the weighs are recorded
 #warning("This method is deprecated and may be removed on future revisions.")
   double samplesMinusOne = (double(samples) - 1.0);
   for (uint16_t i = 0; i < (samples >> 1); i++) {