Arduino EEPROM.read Returns 255 — Complete Guide

In this tutorial, you'll learn about Arduino EEPROM.read Returns 255. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

EEPROM.read() returns 255 (0xFF) instead of the expected stored value.

Quick Fix

Wrong

int val = EEPROM.read(0);  // Returns 255 if address never written

val = 255 (default erased state of EEPROM).

Right

#include <EEPROM.h>

int addr = 10;  // Use address beyond 0

void setup() {
  Serial.begin(9600);
  if (EEPROM.read(addr) == 255) {
    EEPROM.write(addr, 42);
    Serial.println("Initialized EEPROM");
  }
  int val = EEPROM.read(addr);
  Serial.print("Value: ");
  Serial.println(val);
}

void loop() { }

Value: 42  (first run: "Initialized EEPROM").

Prevention

EEPROM reads as 0xFF on fresh devices or after erase. Check for 0xFF and initialize if needed. EEPROM has ~100,000 write cycle endurance. Use addresses starting from 0 but leave room for future expansion. EEPROM.read() does not wear out the memory.

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

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