ESP32: How to use the EEPROM Library for Flash Storage

				
					#include <EEPROM.h>

// Define the size of the virtual EEPROM partition and the memory address
#define EEPROM_SIZE 512       // Allocate 512 bytes
#define CALIBRATION_ADDR 0    // Start address for the float data

// Default/Initial calibration value
const float initialCalibration = 1.05;

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println("\n--- ESP32 EEPROM Emulation Test ---");

  // 1. Allocate the EEPROM space
  if (!EEPROM.begin(EEPROM_SIZE)) {
    Serial.println("Failed to initialize EEPROM!");
    return;
  }
  Serial.print("EEPROM initialized with ");
  Serial.print(EEPROM_SIZE);
  Serial.println(" bytes.");
 
  float storedValue = 0;
 
  // 2. Read the calibration value
  EEPROM.get(CALIBRATION_ADDR, storedValue);

  // --- FIX APPLIED HERE ---
  // The value is likely uninitialized if it reads as NaN.
  // We also check for 0.0 just in case.
  if (isnan(storedValue) || storedValue == 0.0) {
    // 3. Write the initial value if memory is empty or invalid
    Serial.println("Memory uninitialized or invalid (read as NaN). Writing default calibration...");
   
    // Write the initial value
    EEPROM.put(CALIBRATION_ADDR, initialCalibration);
   
    // 4. Commit the changes to Flash
    bool success = EEPROM.commit();
    if (success) {
      Serial.println("Write committed successfully.");
    } else {
      Serial.println("Error committing write!");
    }
   
    // Update the storedValue for subsequent logic and printing
    storedValue = initialCalibration;
   
    Serial.print("Wrote and now using: ");
    Serial.println(storedValue, 3);
  } else {
    // Value was read successfully (and is not NaN)
    Serial.print("Successfully read calibration value: ");
    Serial.println(storedValue, 3);
  }
 
  // 5. Example update: If the current value is 1.05, change it to 1.10
  // Note: We check against the storedValue, which is now guaranteed to be valid.
  if (storedValue == initialCalibration) {
    float newValue = 1.10;
    Serial.print("Current value matches initial value (");
    Serial.print(initialCalibration, 2);
    Serial.print("). Updating calibration to ");
    Serial.print(newValue, 2);
    Serial.println("...");
   
    EEPROM.put(CALIBRATION_ADDR, newValue);
   
    bool success = EEPROM.commit();
    if (success) {
      Serial.println("Update committed successfully.");
    } else {
      Serial.println("Error committing update!");
    }
  }
}

void loop() {
  // Main program runs here.
  delay(5000);
  Serial.println("A reset will be issued to confirm data persistence...");
  ESP.restart();
}