/***
   EEPROM Update method
  
   Stores values read from analog input 0 into the EEPROM.
   These values will stay in the EEPROM when the board is
   turned off and may be retrieved later by another sketch.
  
   If a value has not changed in the EEPROM, it is not overwritten
   which would reduce the life span of the EEPROM unnecessarily.
   
   Released using MIT licence.
 ***/

#include <EEPROM.h>

/** the current address in the EEPROM (i.e. which byte we're going to write to next) **/
int addr = 0;

void setup(){ /** EMpty setup **/ }

void loop()
{
  /***
    need to divide by 4 because analog inputs range from
    0 to 1023 and each byte of the EEPROM can only hold a
    value from 0 to 255.
  ***/
  int val = analogRead(0) / 4;

  /***
    Update the particular EEPROM cell.
    these values will remain there when the board is
    turned off.
  ***/
  EEPROM.update(addr, val);
  
  /***
    The function EEPROM.update(addr, val) is equivalent to the following:
  
    if( EEPROM.read(addr) != val ){
	  EEPROM.write(addr, val);
    }
  ***/
  

  /** advance to the next address.  there are 512 bytes in the EEPROM, so go back to 0 when we hit 512. **/
  addr = addr + 1;
  if (addr == 512)
    addr = 0;

  delay(100);
}