Spectrum Plot example

Examples/FFT_04/FFT_04.ino

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+/*
+
+	Example of use of the FFT libray
+        Copyright (C) 2018 Enrique Condes
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+/*
+  In this example, the Arduino simulates the sampling of a sinusoidal 1000 Hz
+  signal with an amplitude of 100, sampled at 5000 Hz. Samples are stored
+  inside the vReal array. The samples are windowed according to Hamming
+  function. The FFT is computed using the windowed samples. Then the magnitudes
+  of each of the frequencies that compose the signal are calculated. Finally,
+  the frequency spectrum magnitudes are printed. If you use the Arduino IDE
+  serial plotter, you will see a single spike corresponding to the 1000 Hz
+  frecuency.
+*/
+
+#include "arduinoFFT.h"
+
+arduinoFFT FFT = arduinoFFT(); /* Create FFT object */
+/*
+These values can be changed in order to evaluate the functions
+*/
+const uint16_t samples = 64; //This value MUST ALWAYS be a power of 2
+const double signalFrequency = 1000;
+const double samplingFrequency = 5000;
+const uint8_t amplitude = 100;
+/*
+These are the input and output vectors
+Input vectors receive computed results from FFT
+*/
+double vReal[samples];
+double vImag[samples];
+
+void setup()
+{
+  Serial.begin(115200);
+}
+
+void loop()
+{
+  /* Build raw data */
+  double cycles = (((samples-1) * signalFrequency) / samplingFrequency); //Number of signal cycles that the sampling will read
+  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*/
+    vImag[i] = 0.0; //Imaginary part must be zeroed in case of looping to avoid wrong calculations and overflows
+  }
+  FFT.Windowing(vReal, samples, FFT_WIN_TYP_HAMMING, FFT_FORWARD);	/* Weigh data */
+  FFT.Compute(vReal, vImag, samples, FFT_FORWARD); /* Compute FFT */
+  FFT.ComplexToMagnitude(vReal, vImag, samples); /* Compute magnitudes */
+  FFT.PlotSpectrum(vReal, samples, samplingFrequency);
+  double x = FFT.MajorPeak(vReal, samples, samplingFrequency);
+  while(1); /* Run Once */
+  // delay(2000); /* Repeat after delay */
+}