ESP32 RTC Memory Data Lost After Sleep

In this tutorial, you'll learn about ESP32 RTC Memory Data Lost After Sleep. We cover key concepts, practical examples, and best practices.

The Problem

ESP32 data stored in RTC memory disappears after deep sleep wake.

Quick Fix

Wrong

int counter = 0;  // Regular variable - lost on sleep

Counter resets to 0 after each deep sleep cycle.

Right

RTC_DATA_ATTR int bootCount = 0;
void setup() {
  Serial.begin(115200);
  bootCount++;
  Serial.printf("Boot count: %d\n", bootCount);
  esp_sleep_enable_timer_wakeup(5 * 1000000);
  esp_deep_sleep_start();
}

Boot count: 1
Boot count: 2
Boot count: 3
(Count persists across deep sleep)

Prevention

Use RTC_DATA_ATTR to persist variables across deep sleep. RTC memory is 8KB total. Only simple data types survive (no String, no pointers). Use RTC memory for boot counters, calibration data, or sensor state.

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

FAQ