Audio Frequency Detector

1/*
2 File/Sketch Name: AudioFrequencyDetector
3
4 Version No.: v1.0  Created 12 December, 2019
5 
6 Original Author: Clyde A. Lettsome, PhD, PE,  MEM
7 
8 Description:  This code/sketch makes displays the approximate frequency  of the loudest sound detected by a sound detection module. For this project, the  analog output from the 
9 sound module detector sends the analog audio signal  detected to A0 of the Arduino Uno. The analog signal is sampled and quantized (digitized).  A Fast Fourier Transform (FFT) is
10 then performed on the digitized data. The  FFT converts the digital data from the approximate discrete-time domain result.  The maximum frequency of the approximate discrete-time
11 domain result is then  determined and displayed via the Arduino IDE Serial Monitor.
12
13 Note: The arduinoFFT.h  library needs to be added to the Arduino IDE before compiling and uploading this  script/sketch to an Arduino.
14
15 License: This program is free software; you  can redistribute it and/or modify it under the terms of the GNU General Public License  (GPL) version 3, or any later
16 version of your choice, as published by the Free  Software Foundation.
17
18 Notes: Copyright (c) 2019 by C. A. Lettsome Services,  LLC
19 For more information visit https://clydelettsome.com/blog/2019/12/18/my-weekend-project-audio-frequency-detector-using-an-arduino/
20
21*/
22
23#include  "arduinoFFT.h"
24 
25#define SAMPLES 128             //SAMPLES-pt FFT. Must  be a base 2 number. Max 128 for Arduino Uno.
26#define SAMPLING_FREQUENCY 2048  //Ts = Based on Nyquist, must be 2 times the highest expected frequency.
27 
28arduinoFFT  FFT = arduinoFFT();
29 
30unsigned int samplingPeriod;
31unsigned long microSeconds;
32  
33double vReal[SAMPLES]; //create vector of size SAMPLES to hold real values
34double  vImag[SAMPLES]; //create vector of size SAMPLES to hold imaginary values
35 
36void  setup() 
37{
38    Serial.begin(115200); //Baud rate for the Serial Monitor
39    samplingPeriod = round(1000000*(1.0/SAMPLING_FREQUENCY)); //Period in microseconds  
40}
41 
42void loop() 
43{  
44    /*Sample SAMPLES times*/
45    for(int  i=0; i<SAMPLES; i++)
46    {
47        microSeconds = micros();    //Returns the  number of microseconds since the Arduino board began running the current script.  
48     
49        vReal[i] = analogRead(0); //Reads the value from analog pin  0 (A0), quantize it and save it as a real term.
50        vImag[i] = 0; //Makes  imaginary term 0 always
51
52        /*remaining wait time between samples if  necessary*/
53        while(micros() < (microSeconds + samplingPeriod))
54        {
55          //do nothing
56        }
57    }
58 
59    /*Perform FFT on samples*/
60    FFT.Windowing(vReal, SAMPLES, FFT_WIN_TYP_HAMMING, FFT_FORWARD);
61    FFT.Compute(vReal,  vImag, SAMPLES, FFT_FORWARD);
62    FFT.ComplexToMagnitude(vReal, vImag, SAMPLES);
63
64    /*Find peak frequency and print peak*/
65    double peak = FFT.MajorPeak(vReal,  SAMPLES, SAMPLING_FREQUENCY);
66    Serial.println(peak);     //Print out the most  dominant frequency.
67 
68    /*Script stops here. Hardware reset required.*/
69    while (1); //do one time
70}
71