Arduino ESP32 Leveraging Preferences for Permanent Data Retention

preferences.cpp

/*
  In the following example, we will use preferences to record the ESP32 boot times.
*/
#include <Preferences.h>

Preferences preferences;

String str_key_type(int key_type);

void setup() {
  Serial.begin(115200);

  // Open the Preferences with namespace "lonelybinary" with read and write permission
  preferences.begin("lonelybinary", false);
  
  /* 
    try to read the counter from the namespace "lonelybinary"
    if the counter does not exist, it will return a default value of 0
  */
  int counter = preferences.getInt("counter", 0);

  counter++;

  // Print the counter to Serial Monitor
  Serial.printf("Current reboot counter value: %u\n", counter);

  Serial.print("Is key Exist? : ");
  Serial.println(preferences.isKey("counter") ? "Yes" : "No");

  Serial.print("Key Type : ");
  Serial.println(str_key_type(preferences.getType("counter")));

  // Store the counter to the Preferences
  preferences.putUInt("counter", counter);

  // Close the Preferences
  preferences.end();

  Serial.println("Restarting in 30 seconds...");
  delay(30000);
  ESP.restart();
}

void loop() {}

String str_key_type(int key_type) {
  switch (key_type) {
    case PT_I8:
      return "PT_I8";
    case PT_U8:
      return "PT_U8";
    case PT_I16:
      return "PT_I16";
    case PT_U16:
      return "PT_U16";
    case PT_I32:
      return "PT_I32";
    case PT_U32:
      return "PT_U32";
    case PT_I64:
      return "PT_I64";
    case PT_U64:
      return "PT_U64";
    case PT_STR:
      return "PT_STR";
    case PT_BLOB:
      return "PT_BLOB";
    case PT_INVALID:
      return "PT_INVALID";
    default:
      return "UNKNOWN";
  }
}