Audio Spectrum Analyzer

Finally managed to have my Arduino Uno ‘spectrualize’ audio on a 1.3″ monochrome 128×64 oled screen. These small oled screens are amazingly fast!

Sound quality of the video is limited because the music (“Golden Brown” by The Stranglers) was picked up from a small laptop speaker.

The upper part of the screen shows a peak level indicator.

The sketch uses a Fast Fourier Transformation library that I found on Internet. It translates the signal from the time domain to the frequency domain. [Some comments are in Dutch]

/*
  Arduino Spectrum Analyzer
*/

#include <fix_fft.h>                                  //library to perfom the Fast Fourier Transform

//#include <SPI.h>                                    //SPI library
#include <Wire.h>                                     //I2C library for OLED
#include <Adafruit_GFX.h>                             //graphics library for OLED
#include <Adafruit_SH1106.h>                          //OLED driver

#define OLED_RESET 4                                  //OLED reset, not hooked up but required by library
Adafruit_SH1106 display(OLED_RESET);                  //declare instance of OLED library called display

char im[64], data[64];                                //variables for the FFT
char x = 0, ylim = 60;                                //variables for drawing the graphics
int i = 0, val;                                       //counters
int dropMax = 0;
int curMax;

void setup()
{
  // Serial.begin(9600);                                //serial comms for debuging
  display.begin(SH1106_SWITCHCAPVCC,0x3C);              //begin OLED @ hex addy 0x3C
  display.setTextSize(1);                               //set OLED text size to 1 (1-6)
  display.setTextColor(WHITE);                          //set text color to white
  display.clearDisplay();                               //clear display
  //analogReference(DEFAULT);                           // Use default aref voltage (5V op UNO).
  analogReference(EXTERNAL);                            // voeding naar microphone breakout ook met AREF verbinden
};

void loop()
{
  int min=1024, max=0;                                //set minumum & maximum ADC values
  for (i = 0; i < 64; i++) {                          //take 128 samples
    val = analogRead(A0);                             //get audio from Analog 0
    data[i] = val / 4 - 128;                          //each element of array is val/4-128
    im[i] = 0;                                        
    if(val>max) max=val;                              //capture maximum level
    if(val<min) min=val;                              //capture minimum level
  };
  // Serial.println(max-min); // blijkt tussen 0 en 512 te liggen
  // data bevat reeel en im imaginair deel van de meting; im hier op 0 gesteld
  // 3-de parameter m, dan zijn er 2^m 'bins'; als m=7 dan dus 128; alleen de eerste helft (64) bevatten de bruikbare waarden
  fix_fft(data, im, 6, 0);                            //perform the FFT on data
  
  display.clearDisplay();                             //clear display
  // de eerste 32 array elementen bevatten na fix_fft de reeele waarden
  for (i = 1; i < 32; i++) {                          // In the current design, 60Hz and noise
    int dat = sqrt(data[i] * data[i] + im[i] * im[i]);//filter out noise and hum
    // vermenigvuldigingsfactor zorgt dat het er met het microfoonbordje dan beter uitziet (loopt af van 2 tot 1)
    dat = (2-dat/60)*dat;
    // de +5 zorgt dat de achtergrondruis over de volle breedte onzichtbaar wordt
    display.drawLine(0,63,128,63,WHITE);  // baseline
    display.fillRect(i*4 + x, ylim-dat+5, 2, 63-ylim+dat, WHITE); // draw bar graphics for freqs above 500Hz to buffer
  };                                                
  display.setCursor(0,0);                             //set cursor to top of screen
  // gewogen gemiddelde tussen nieuwe en oude waarde; deelfactor 4 omdat max-min in range 0-512 zit; -12 is compensatie
  curMax=(dropMax+2*min((max-min)/4-12,128))/3;       
  display.fillRect(0,0,curMax,3,WHITE);
  if (dropMax>curMax+4) {
    dropMax=dropMax-3;
    display.fillRect(dropMax-4,0,3,3,WHITE);
  } else {
    dropMax=curMax;
  }
  
  display.display();                                  //show the buffer
};

Arduino Spectrum Analyzer

#include <fix_fft.h> //library to perfom the Fast Fourier Transform

//#include <SPI.h> //SPI library

#include <Wire.h> //I2C library for OLED

#include <Adafruit_GFX.h> //graphics library for OLED

#include <Adafruit_SH1106.h> //OLED driver

#define OLED_RESET 4 //OLED reset, not hooked up but required by library

Adafruit_SH1106 display(OLED_RESET); //declare instance of OLED library called display

char im[64], data[64]; //variables for the FFT

char x = 0, ylim = 60; //variables for drawing the graphics

int i = 0, val; //counters

int dropMax = 0;

int curMax;

void setup()

{

// Serial.begin(9600); //serial comms for debuging

display.begin(SH1106_SWITCHCAPVCC,0x3C); //begin OLED @ hex addy 0x3C

display.setTextSize(1); //set OLED text size to 1 (1-6)

display.setTextColor(WHITE); //set text color to white

display.clearDisplay(); //clear display

//analogReference(DEFAULT); // Use default aref voltage (5V op UNO).

analogReference(EXTERNAL); // voeding naar microphone breakout ook met AREF verbinden

};

void loop()

{

int min=1024, max=0; //set minumum & maximum ADC values

for (i = 0; i < 64; i++) { //take 128 samples

val = analogRead(A0); //get audio from Analog 0

data[i] = val / 4 - 128; //each element of array is val/4-128

im[i] = 0;

if(val>max) max=val; //capture maximum level

if(val<min) min=val; //capture minimum level

};

// Serial.println(max-min); // blijkt tussen 0 en 512 te liggen

// data bevat reeel en im imaginair deel van de meting; im hier op 0 gesteld

// 3-de parameter m, dan zijn er 2^m 'bins'; als m=7 dan dus 128; alleen de eerste helft (64) bevatten de bruikbare waarden

fix_fft(data, im, 6, 0); //perform the FFT on data

display.clearDisplay(); //clear display

// de eerste 32 array elementen bevatten na fix_fft de reeele waarden

for (i = 1; i < 32; i++) { // In the current design, 60Hz and noise

int dat = sqrt(data[i] * data[i] + im[i] * im[i]);//filter out noise and hum

// vermenigvuldigingsfactor zorgt dat het er met het microfoonbordje dan beter uitziet (loopt af van 2 tot 1)

dat = (2-dat/60)*dat;

// de +5 zorgt dat de achtergrondruis over de volle breedte onzichtbaar wordt

display.drawLine(0,63,128,63,WHITE); // baseline

display.fillRect(i*4 + x, ylim-dat+5, 2, 63-ylim+dat, WHITE); // draw bar graphics for freqs above 500Hz to buffer

};

display.setCursor(0,0); //set cursor to top of screen

// gewogen gemiddelde tussen nieuwe en oude waarde; deelfactor 4 omdat max-min in range 0-512 zit; -12 is compensatie

curMax=(dropMax+2*min((max-min)/4-12,128))/3;

display.fillRect(0,0,curMax,3,WHITE);

if (dropMax>curMax+4) {

dropMax=dropMax-3;

display.fillRect(dropMax-4,0,3,3,WHITE);

} else {

dropMax=curMax;

}

display.display(); //show the buffer

};