Arduino EEPROM.write Not Saving Data

In this tutorial, you'll learn about Arduino EEPROM.write Not Saving Data. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

Values written with EEPROM.write() are lost after power cycle.

Quick Fix

Wrong

EEPROM.write(0, 42);  // Called in loop too often, wears EEPROM

EEPROM wears out quickly or value lost due to frequent writes.

Right

#include <EEPROM.h>

int lastVal = -1;

void saveValue(int val) {
  int addr = 0;
  if (val != lastVal) {  // Only write on change
    EEPROM.write(addr, val);
    lastVal = val;
    Serial.print("Saved: ");
    Serial.println(val);
  }
}

void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensor = analogRead(A0) / 4;  // 0-255
  saveValue(sensor);
  delay(100);
}

Saved: 42  (only when value changes).

Prevention

Always check if the value changed before writing to EEPROM. A single EEPROM.write() takes ~3.3 ms on AVR (during which interrupts may be disabled). For multi-byte values, use EEPROM.put(). For frequently changing data, store in RAM and save to EEPROM periodically.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ