#include <EEPROM.h>

int interval = 5;  //Counter refresh and save interval

int wh_start, wh_total;
int pulseCount, crontimer;
 
void setup() {
Serial.begin(9600);
attachInterrupt(0, onPulse, FALLING);
}

void loop() {
  if(millis()/1000 > crontimer+interval){
    crontimer = millis()/1000;
    wh_total = read_counter(0);
    wh_total = wh_total+pulseCount;
    save_counter(0, wh_total);
    pulseCount = 0; 
    
    Serial.print("Start Wh: ");
    Serial.println(wh_start);
    Serial.print("Total Wh: ");
    Serial.println(wh_total);
    Serial.println("================");
  }
}

int read_counter(int address)
{
  long byte_2 = EEPROM.read(address);
  long byte_1 = EEPROM.read(address + 1);
  return ((byte_2 << 0) & 0xFFFFFF) + ((byte_1 << 8) & 0xFFFFFFFF);
}

void save_counter(int address, int value)
{
  byte byte_2 = (value & 0xFF);
  byte byte_1 = ((value >> 8) & 0xFF);
  EEPROM.update(address, byte_2);
  EEPROM.update(address + 1, byte_1);
}

void onPulse()
{
    pulseCount++;
    wh_start++;
}