// sketch_13_06_FFT_Spectrum

#include "fix_fft.h"

const int analogPin = A0;
const long GAIN = 5;
char im[128];
char data[128];

const byte PS_128 = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);
const byte PS_16 = (1 << ADPS2);


void setup()
{
  Serial.begin(9600);
  ADCSRA &= ~PS_128;  // remove prescale of 128
  ADCSRA |= PS_16;    // add prescale of 16 (1MHz)
}

void loop()
{
  sampleWindowFull();
  fix_fft(data, im, 7, 0);
  updateData();

  showSpectrum();
}

void sampleWindowFull()
{
  for (int i = 0; i < 128; i++)
  {                               
    int val = (analogRead(analogPin) - 512) * GAIN;                       
    data[i] = val / 4;               
    im[i] = 0;     
  }
}

void updateData()
{
  for (int i = 0; i < 64; i++)
  {
    data[i] = sqrt(data[i] * data[i] + im[i] * im[i]); 
  }
}


void showSpectrum()
{
  for (int i = 1; i < 64; i++)
  {
    int p = data[i];
    Serial.print(p);
    Serial.print(",");
  }
  Serial.println();
}