*//There are 2 ways to wake up a system, those are called Interrupts. 
*//hardware Interrupts are based on external events where signals are sent to the GPIO.
*//Software Interrupts occur when we program the device, like through a wake up alarm or timer.
 
#define uS_TO_S_FACTOR 1000000           *//Equation to convert milliseconds to Minutes
#define TIME_TO_SLEEP  10                *//Determined amount of minutes at sleep
 
RTC_DATA_ATTR int bootCount = 0;         
 
*//Data has to be stored in the Real time Clock (RTC) fast memory because the CPU memory is wiped on every boot.
*// The amount of data has to be minimal due to size limitations : 8bit fast memory and 8bit Slow memory.
 
*//Power outages and resetting the board will erase the RTC memory, therefore its use should be limited to non essential information.
*//Therefore we decided to just Keeping data of times awaken in internal RTC, this will help us see if any issues occur.
 
 
 
**************Wake Up Print **************************************************************
 
void print_wakeup_reason(){                       *//Set up to list reasons for system wake-up
  esp_sleep_wakeup_cause_t wakeup_reason;
 
  wakeup_reason = esp_sleep_get_wakeup_cause();   *//System wakes up due to 3 reasons
 
  switch(wakeup_reason)                           
  {
    case ESP_SLEEP_WAKEUP_EXT0 : Serial.println("PUSHED BUTTON caused the system to WAKEUP"); break;
    case ESP_SLEEP_WAKEUP_TIMER : Serial.println("TIMER caused the system to WAKEUP"); break;
    default : Serial.printf("DeepSleep didn't wake up ESP32: %d\n",wakeup_reason); break;   *//Initial Boot will yield this reason
  }
}
 
*//We made the system wake up due to the internal timer and a pushed button,
*// the reason for the push button is that in the case we can take a measurement at our will without having to wait for the timers.
*//An external clock could be added to the device, however Grafana already designates time and date of transferred data.
 
void setup(){                  
  Serial.begin(115200);
  delay(1000);                 
 
  pinMode(32,OUTPUT);         *//Illuminates a LED when the system is awake. For visual confirmation.
 
  pinMode(33,INPUT_PULLUP);   
 
   *//ESP32 has pull-up resistors built on the pins, when we activate it
   *//it avoids the use of external resistors 
   *//INPUT_PULLUP keeps the signal HIGH by default
   *//floating currents which can produce erroneous readings are avoided by pull up/down resistors
 
 
 
  for(int i=0;i<5;i++)         
{
  digitalWrite(32,HIGH);       *// These are the parameters for the LED flashing 
  delay(1000);
  digitalWrite(32,LOW);
  delay(1000);
  }
 
 
 
  ++bootCount;
  Serial.println("Reboot count number: " + String(bootCount));     *//We want to know how many times the system has booted
                                                                   *//easy way to know if there are issues internal or battery 
                                                                   *//issues
 
  print_wakeup_reason();
 
 
 
  esp_sleep_enable_ext0_wakeup(GPIO_NUM_33,0);                 
 
*//During Sleep only Pins connected to the RTC are operational
*//A General Purpose Input/output pin are used to perform digital readings and output functions.
*//By default those pins have no predefined purpose.
*//The pin used has to be named after their GPIO 
 
 
 
 
  esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);                   *//conversion factor to minutes
 
  Serial.println("ESP32 is going into DeepSleep for " + String(TIME_TO_SLEEP) +    *//Script detailing the process
  " Seconds");
 
 
  Serial.println("Going to sleep now......");                                       
  delay(1000);
  Serial.flush();                                                                  *//To avoid mistakes in data transmission by 
                                                                                   *//clearing buffer
  esp_deep_sleep_start();
 
}