Arduino flicker meter-Determining the quality of light bulbs

// flicker_meter
//   compute flicker index
// Sketch is for illustrative purposes only  The sketch is  provided as is without any guarantees or warranty or suitability to purpose.
//
// electronupdate@gmail.com
//
//  dependencies:
//  - u8glib required for driving OLED display
//  - Ardunio Nano rev 3
//  - 128 x 64 OLED display. i2c interface... "heltec.cn"
//  - 1 push button switch
//  - Light sensor
//  - extrernal vref

#include "U8glib.h"
#include <Wire.h> //I2C Arduino Library
#include "TimerOne.h"

U8GLIB_SH1106_128X64 u8g(U8G_I2C_OPT_NONE); // I2C / TWI ** this is specific to the OLED panel in use... refer to google's library to select different (huge # of panels supported!)

bool display_mode = 0;   //when in mode zero it shows numeric results, when in mode one, graphically
int processed = 0; // zero if sample buffer consumed otherwise 1
int cycle;
int inPin1 = 12;  
int inPin2 = 11;
int inPin3 = 10;
int button1, button2, button3;
int control_pin = 3;
int i;
int sample_buffer[129];
int sample_pos = 0;
int full_flag = 0;
int sample_min = 1023;
int sample_max = 0;
int min_final = 1023;
int max_final = 0;
int light_sample = 0;
float percent_flicker = 0;
float scale_factor;


void draw(void) {
  // graphic commands to redraw the complete screen should be placed here  
  char temp[50];
  char temp1[50];
  char temp2[50];
  u8g.setFont(u8g_font_unifont);

      percent_flicker = ((max_final - min_final)* 100/(max_final ));

      //noise filter... at really dark levels to prevent error readings of 100% flicker 
       if (min_final<1)                    //if ((max_final - min_final) < 4)
        { percent_flicker = 0;
        }
if (display_mode == 0)
  {
     
  
    // convert numbers into strings so they can  be displayed
      // adriundo or u8g lib never implemented sprintf
      sprintf(temp1,"%d",min_final);
      sprintf(temp2,"%d",max_final);
      dtostrf(percent_flicker,4, 1, temp);
      u8g.drawStr(0,15, "Low:");
      u8g.drawStr(0,27, "High:");
      u8g.drawStr(0,57, "%: ");
      u8g.drawStr(45,15, temp1);
      u8g.drawStr(45,27, temp2);
      u8g.drawStr(45,57,temp);
      sprintf(temp,"%d",display_mode);
      u8g.drawStr(80,15, "Flick.");  
      u8g.drawStr(80,27, "meter");  
      // keyboard check code, uncomment to display key press state
      //if (button1 == 0) {u8g.drawStr(80,10,"1");} else {u8g.drawStr(80,10,"0"); };
      //if (button2 == 0) {u8g.drawStr(90,10,"1");} else {u8g.drawStr(90,10,"0"); };
      //if (button3 == 0) {u8g.drawStr(50,30,"1");} else {u8g.drawStr(50,30,"0"); };
   } 
  
 else
  {
    if (max_final-min_final > 63)
    
    {scale_factor = (float) 63/(max_final - min_final);}
    else 
    {scale_factor = 2;}
    //scale_factor = 1;
    for (i = 0; i < 127; i++)
       {
        u8g.drawPixel(i,(double) (scale_factor * (float)(sample_buffer[i]-min_final)));
     
    }
    

  };  

}

void setup(){
 // some control buttons
  pinMode(inPin1, INPUT_PULLUP);  //delay time down
   pinMode(inPin2, INPUT_PULLUP);  //delay time up
  pinMode(inPin3, INPUT_PULLUP);  // arm system
  pinMode(A0, INPUT);
  
  analogReference( EXTERNAL);
  
  
  Timer1.initialize(100); // timer running at 0.1 ms (i.e. 10KHz sample rate
  Timer1.attachInterrupt (timerIsr); 
      
    //setup oled screen
  if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
    u8g.setColorIndex(255);     // white
  }
  else if ( u8g.getMode() == U8G_MODE_GRAY2BIT ) {
    u8g.setColorIndex(3);         // max intensity
  }
  else if ( u8g.getMode() == U8G_MODE_BW ) {
    u8g.setColorIndex(1);         // pixel on
  }
  else if ( u8g.getMode() == U8G_MODE_HICOLOR ) {
    u8g.setHiColorByRGB(255,255,255);
  }
    
}

void timerIsr()
{
  if (processed == 1)
  {
   light_sample = analogRead(0);
   
   sample_buffer[sample_pos] = light_sample;
   
   if (light_sample < sample_min)  sample_min = light_sample;
   if (light_sample >sample_max )  sample_max = light_sample;
   
   sample_pos++;
   
   if (sample_pos == 128)
      { 
        sample_pos =0;
        min_final = sample_min;
        max_final = sample_max;
        
        sample_min = 1023;
        sample_max = 0;
        processed = 0;  // set a flag telling main routine there is a data set to process
      }
   
  }

}


void loop(){
  
// inint oled

  
  button1 = digitalRead(inPin1);
  button2 = digitalRead(inPin2);
  button3 = digitalRead(inPin3);  

  if (button1 == 0) { display_mode = display_mode ^ 1; 
             delay(100);
           } // toggle between numeric and graphic  

  u8g.firstPage();      
   do { 
            draw();
     
      }  while( u8g.nextPage() );

processed = 1;
 delay(100);  
   
}