New example.

Obtain frequency of a signal sampled through the ADC.

Examples/FFT_03/FFT_03.ino

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+/*
+
+	Example of use of the FFT libray to compute FFT for a signal sampled through the ADC.
+        Copyright (C) 2017 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/>.
+
+*/
+
+#include "arduinoFFT.h"
+
+arduinoFFT FFT = arduinoFFT(); /* Create FFT object */
+/*
+These values can be changed in order to evaluate the functions
+*/
+#define CHANNEL A0
+const uint16_t samples = 64; //This value MUST ALWAYS be a power of 2
+double samplingFrequency = 200;
+
+unsigned int delayTime = 0;
+
+/*
+These are the input and output vectors
+Input vectors receive computed results from FFT
+*/
+double vReal[samples];
+double vImag[samples];
+
+#define SCL_INDEX 0x00
+#define SCL_TIME 0x01
+#define SCL_FREQUENCY 0x02
+
+void setup()
+{
+  if(samplingFrequency<=1000)
+    delayTime = 1000/samplingFrequency;
+  else
+    delayTime = 1000000/samplingFrequency;
+  Serial.begin(115200);
+  Serial.println("Ready");
+}
+
+void loop()
+{
+  for(uint16_t i =0;i<samples;i++)
+  {
+    vReal[i] = double(analogRead(CHANNEL));
+    if(samplingFrequency<=1000)
+      delay(delayTime);
+    else
+      delayMicroseconds(delayTime);
+  }
+  /* Print the results of the sampling according to time */
+  Serial.println("Data:");
+  PrintVector(vReal, samples, SCL_TIME);
+  FFT.Windowing(vReal, samples, FFT_WIN_TYP_HAMMING, FFT_FORWARD);	/* Weigh data */
+  Serial.println("Weighed data:");
+  PrintVector(vReal, samples, SCL_TIME);
+  FFT.Compute(vReal, vImag, samples, FFT_FORWARD); /* Compute FFT */
+  Serial.println("Computed Real values:");
+  PrintVector(vReal, samples, SCL_INDEX);
+  Serial.println("Computed Imaginary values:");
+  PrintVector(vImag, samples, SCL_INDEX);
+  FFT.ComplexToMagnitude(vReal, vImag, samples); /* Compute magnitudes */
+  Serial.println("Computed magnitudes:");
+  PrintVector(vReal, (samples >> 1), SCL_FREQUENCY);
+  double x = FFT.MajorPeak(vReal, samples, samplingFrequency);
+  Serial.println(x, 6);
+  while(1); /* Run Once */
+
+}
+
+void PrintVector(double *vData, uint8_t bufferSize, uint8_t scaleType)
+{
+  for (uint16_t i = 0; i < bufferSize; i++)
+  {
+    double abscissa;
+    /* Print abscissa value */
+    switch (scaleType)
+    {
+      case SCL_INDEX:
+        abscissa = (i * 1.0);
+	break;
+      case SCL_TIME:
+        abscissa = ((i * 1.0) / samplingFrequency);
+	break;
+      case SCL_FREQUENCY:
+        abscissa = ((i * 1.0 * samplingFrequency) / samples);
+	break;
+    }
+    Serial.print(abscissa, 6);
+    Serial.print(" ");
+    Serial.print(vData[i], 4);
+    Serial.println();
+  }
+  Serial.println();
+}