32 band spectrum indicator for OLED

/*Copyright (c) 2019 Shajeeb TM
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE. */

#include <arduinoFFT.h>
#include <SPI.h>
//#include <Adafruit_GFX.h>                           //graphics library for OLED
#include <Adafruit_SH1106.h>                          //OLED driver
#include <Fonts/Picopixel.h>                     //selecting specific font from Adafruit GFX library

// SH1106 HW SPI, SDA-MOSI-11, CLK-13
#define OLED_DC     6
#define OLED_CS     7
#define OLED_RESET  8
Adafruit_SH1106 display(OLED_DC, OLED_RESET, OLED_CS);

#define SAMPLES 64            //Must be a power of 2
#define  xres 32              // Total number of  columns in the display, must be <= SAMPLES/2
#define  yres 60

int yvalue;
double vReal[SAMPLES];
double vImag[SAMPLES];
const int buttonPin = 5;               // the number of the pushbutton pin
int state = HIGH;                      // the current reading from the input pin
int previousState = LOW;               // the previous reading from the input pin
//unsigned long lastDebounceTime = 0;  // the last time the output pin was toggled
//unsigned long debounceDelay = 50;    // the debounce time; increase if the output flickers

arduinoFFT FFT = arduinoFFT();                                    // FFT object

void setup() {
//Serial.begin(9600);
  display.begin(SH1106_SWITCHCAPVCC);
  display.setTextSize(1);                             //set OLED text size to 1 (1-6)
  display.setTextColor(WHITE);                        //set text color to white
  display.clearDisplay();                             //clear display

  ADCSRA = 0b11100101;        // Set the Analog Digital Convetor Status Register A to free running mode and set pre-scalar to 32 (0xe5)
//ADCSRA = 0b11100100;        // changed last bit to change division factor from 32 to 16, to spread the display out of the left edge. It might not be as pure as original but visually provides more width.
    ADMUX = 0b00000000;       // use pin A0 and external voltage reference
    pinMode(buttonPin, INPUT);
    delay(50);                // wait to get reference voltage stabilized
/*
    for(int i=0; i<xres; i++)
        {peaks[i]=0;
Serial.print("peaks[i]: "); Serial.print(peaks[i]); Serial.println(" ");
        }
*/
}

void loop() {

char data_avgs[xres];
int peaks[xres];

   // ++ Sampling
   for(int i=0; i<SAMPLES; i++)
    {
      while(!(ADCSRA & 0x10));        // wait for ADC to complete current conversion ie ADIF bit set
      ADCSRA = 0b11110101 ;               // clear ADIF bit so that ADC can do next operation (0xf5)
      int value = ADC - 512 ;                 // Read from ADC and subtract DC offset caused value
      vReal[i]= value/8;                      // Copy to bins after compressing. Division by 8 reduces the amplitude of the measured input so that it can be uniformly (vertical) fit in the display used
      vImag[i] = 0;
//Serial.print("value: "); Serial.print(value); Serial.println(" ");
    }
    // -- Sampling


    // ++ FFT
    FFT.Windowing(vReal, SAMPLES, FFT_WIN_TYP_HAMMING, FFT_FORWARD);
    FFT.Compute(vReal, vImag, SAMPLES, FFT_FORWARD);
    FFT.ComplexToMagnitude(vReal, vImag, SAMPLES);
    // -- FFT


    // ++ re-arrange FFT result to match with no. of columns on display ( xres )
    int step = (SAMPLES/2)/xres;
    int c=0;
    for(int i=0; i<(SAMPLES/2); i+=step)
    {
      data_avgs[c] = 0;
      for (int k=0 ; k< step ; k++) {
          data_avgs[c] = data_avgs[c] + vReal[i+k];
      }
      data_avgs[c] = data_avgs[c]/step;
      c++;
    }
    // -- re-arrange FFT result to match with no. of columns on display ( xres )


    // ++ send to display according measured value
    display.clearDisplay();                             //clear display
    for(int i=0; i<xres; i++)
    {
      data_avgs[i] = constrain(data_avgs[i],0,80);            // set max & min values for buckets
      data_avgs[i] = map(data_avgs[i], 0, 80, 0, yres+26);        // remap averaged values to yres +16 pixels for the title
      yvalue=data_avgs[i];

// Serial.print("yvalue: "); Serial.print(yvalue); Serial.println("   ");


      if (yvalue > peaks[i]) peaks[i] = yvalue ;
          peaks[i] = peaks[i]-1;


/*
      peaks[i] = peaks[i]-1;    // decay by one light
      if (yvalue > peaks[i])
          peaks[i] = yvalue ;
      yvalue = peaks[i];
*/

   //Drawing columns
     display.drawLine(i*4,   yres, i*4,   yres-yvalue, WHITE);
//   display.drawLine(i*4+1, yres, i*4+1, yres-yvalue, WHITE);  // 2 pixel thick column
//   display.drawLine(i*4+2, yres, i*4+2, yres-yvalue, WHITE);  // 3 pixel thick column
//   display.drawLine(i*4+3, yres, i*4+3, yres-yvalue, WHITE);  // 4 pixel thick column

//       display.drawPixel(i*4, yres-peaks[i], WHITE);              //Drawing dots for peaks
     }
     // -- send to display according measured value


  display.setFont(&Picopixel);
  display.setCursor(0,4);                             //set cursor to top of screen
  display.print("      32 Channel Spectrum Indicator");             //print title to buffer
  display.display();                                  //show the buffer
 }