arduino How to store variables in EEPROM and use them for permanent storage


Syntax

  • EEPROM.write(address, value); //(Store variables in EEPROM in a particular address)
  • EEPROM.read(address); //(Retrieve values from EEPROM and read data stored in EEPROM)

Parameters

Parameters of EEPROM.writeDetail
addressThe address where value is to be stored in EEPROM
valueMain variable to store in EEPROM. Note that this is a uint_8 (single byte)—you must split multiple-byte data types into single bytes yourself. Or you can use EEPROM.put to store floats or other data types.
Parameters of EEPROM.ReadDetail
addressThe address from which the variable is to be read

Remarks

The allowable addresses vary by hardware.

  • ATMega328 (Uno, Pro Mini, etc.): 0–1023
  • ATMega168: 0-511
  • ATMega1280: 0-4095
  • ATMega2560: 0-4095

source

Store a variable in EEPROM and then retrieve it and print to screen

First, add a reference to <EEPROM.h> at the start of your sketch:

#include <EEPROM.h>

Then your other code:

// Stores value in a particular address in EEPROM. There are almost 512 addresses present.

    // Store value 24 to Address 0 in EEPROM
    int addr = 0;
    int val = 24;
    EEPROM.write(addr, val);     // Writes 24 to address 0
    
    // ---------
    // Retrieves value from a particular address in EEPROM
    // Retrieve value from address 0 in EEPROM
    int retrievedVal = EEPROM.read(0);    // Retrieves value stored in 0 address in
                                          // EEPROM

    // *[NOTE: put Serial.begin(9600); at void setup()]*
    Serial.println(retrievedVal);        // Prints value stored in EEPROM Address 0 to 
                                         // Serial (screen)