#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

const float voltageDividerRatio = 2.0; // ratio de diviseur de tension
const float batteryVoltageMax = 4.2; // tension maximale de la batterie en pleine charge
const float batteryVoltageMin = 3.2; // tension minimale de la batterie en fin de décharge
const float batteryVoltageRange = batteryVoltageMax - batteryVoltageMin; // plage de tension de la batterie


int counter = 0;

int battery_level_pc = 100;


Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire);

void setup() {
  
  Serial.begin(9600);  
  Serial.println(F("Started"));
  
  //=========================================================================
  // I2C Address is 0x3D for those screens
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }
  //=========================================================================


  pinMode(A0, INPUT);// ADC


  
  //Say Hello!
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setCursor(0,10);
  display.setTextSize(1);
  display.println("Hello Telecom Paris");
  display.display();
  delay(2000);
}

void loop() {

  display.clearDisplay();

  //Display raw value on left
  display.setCursor(60,0);
  display.setTextSize(2);
  display.println(counter);


  battery_level_pc = getBatteryLevel();
  displayProgressBar(battery_level_pc);

  
  //update screen
  display.display();
  delay(500); 


  counter++;
  
}

int getBatteryLevel(){
  float Vbatt = 0;
  //In addition, during communication in particular, spike-like errors occurred, which had to be averaged out 16 times to remove them.
  for(int i = 0; i < 16; i++) {
    Vbatt = Vbatt + analogReadMilliVolts(A0); // ADC with correction   
  }
  float Vbattf = 2 * Vbatt / 16 / 1000.0;     // attenuation ratio 1/2, mV --> V

  int batteryPercentage = 100* (Vbattf - batteryVoltageMin) / batteryVoltageRange;

  return(batteryPercentage);
}


void displayProgressBar(int progress_value){
  Serial.println(progress_value*display.width()/100.);
  display.fillRect(0, SCREEN_HEIGHT/2, progress_value*display.width()/100., 5, SSD1306_INVERSE);
}