Generate random numbers and UUIDs on the ESP8266 and ESP32 using the hardware RNG. Due to changes in requirements, I have moved to a different approach which has been implemented in the following library: ESP UUID. It supports ArduinoJson and std::map. Pull requests will be accepted here, but no active contribution from my side will be made.

#include "Arduino.h"
#include "ESPRandom.h"

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

void loop() {
  Serial.println(ESPRandom::get());
  delay(1000);
}

#include "Arduino.h"
#include "ESPRandom.h"

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

void loop() {
  uint8_t uuid[16];
  ESPRandom::uuid(uuid);
  Serial.println(ESPRandom::uuidToString(uuid));
  delay(1000);
}

For random numbers to be generated, the radio (WiFi or Bluetooth) have to be active. Therefore, when getting a random number (or UUID) it will check if WiFi is active and activate it (in station mode) if this is not the case.

Another reason for creating this library is that the alternatives are covered in copy-left licences which significantly restrict their use.

Derived the UUID v1 generation algorithm from the stduuid library.