void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  uint8_t base_mac_addr[6] = {0};
  esp_err_t ret = ESP_OK;
  ret = esp_efuse_mac_get_default(base_mac_addr);
  printf("MAC Address = %02x:%02x:%02x:%02x:%02x:%02x (ret: %d)\n", 
    base_mac_addr[0],
    base_mac_addr[1],
    base_mac_addr[2],
    base_mac_addr[3],
    base_mac_addr[4],
    base_mac_addr[5],
    ret
  );
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
}