arduino-esp32/libraries/EEPROM/examples/eeprom_write/eeprom_write.ino

/*
   EEPROM Write

   Stores random values 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)
int addr = 0;
#define EEPROM_SIZE 64
void setup()
{
  Serial.begin(115200);
  Serial.println("start...");
  if (!EEPROM.begin(EEPROM_SIZE))
  {
    Serial.println("failed to initialise EEPROM"); delay(1000000);
  }
  Serial.println(" bytes read from Flash . Values are:");
  for (int i = 0; i < EEPROM_SIZE; i++)
  {
    Serial.print(byte(EEPROM.read(i))); Serial.print(" ");
  }
  Serial.println();
  Serial.println("writing random n. in memory");
}

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(10) / 4;
  int val = byte(random(10020));
  // 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);
  Serial.print(val); Serial.print(" ");
  // advance to the next address.  there are 512 bytes in
  // the EEPROM, so go back to 0 when we hit 512.
  // save all changes to the flash.
  addr = addr + 1;
  if (addr == EEPROM_SIZE)
  {
    Serial.println();
    addr = 0;
    EEPROM.commit();
    Serial.print(EEPROM_SIZE);
    Serial.println(" bytes written on Flash . Values are:");
    for (int i = 0; i < EEPROM_SIZE; i++)
    {
      Serial.print(byte(EEPROM.read(i))); Serial.print(" ");
    }
    Serial.println(); Serial.println("----------------------------------");
  }

  delay(100);
}