framework-arduinoteensy-cxx20/libraries/EEPROM/examples/eeprom_write/eeprom_write.ino

/*
 * EEPROM Write
 *
 * 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.
 */

#include <EEPROM.h>

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

  /***
    Write the value to the appropriate byte of the EEPROM.
    these values will remain there when the board is
    turned off.
  ***/

  EEPROM.write(addr, val);

  /***
    Advance to the next address, when at the end restart at the beginning.

    Larger AVR processors have larger EEPROM sizes, E.g:
    - Arduno Duemilanove: 512b EEPROM storage.
    - Arduino Uno:        1kb EEPROM storage.
    - Arduino Mega:       4kb EEPROM storage.
    - Teensy 3.0 & 3.1:   2kb EEPROM storage.
    - Teensy-LC:          128b EEPROM storage.
    - Teensy 2.0:         1kb EEPROM storage.
    - Teensy++ 2.0:       4kb EEPROM storage.

    Rather than hard-coding the length, you should use the pre-provided length function.
    This will make your code portable to all AVR processors.
  ***/
  addr = addr + 1;
  if(addr == EEPROM.length())
    addr = 0;

  /***
    As the EEPROM sizes are powers of two, wrapping (preventing overflow) of an
    EEPROM address is also doable by a bitwise and of the length - 1.

    ++addr &= EEPROM.length() - 1;
  ***/


  delay(100);
}