byte ar[6] = { 12, 23, 34, 45, 56, 78 };

#include <WiFi.h>

void setup() {
  // put your setup code here, to run once:
  
  Serial.begin(115200);
  Serial.print("Start ");
  Serial.println(__FILE__);

  uint8_t mac[6];
  esp_read_mac(mac, ESP_MAC_WIFI_STA);
  
  Serial.print("MAC Address: ");
  for (int i = 0; i < 6; i++) {
    Serial.printf("%02X", mac[i]);
    if (i < 5) Serial.print(":");
  }
  Serial.println();

  uint8_t base_mac_addr[6] = {0};
  esp_err_t ret = ESP_OK;
  ret = esp_efuse_mac_get_default(base_mac_addr);
  /*
  Serial.printf("ID Address = %02x:%02x:%02x:%02x:%02x:%02x (ret: %d)\n", 
    base_mac_addr[5],
    base_mac_addr[4],
    base_mac_addr[3],
    base_mac_addr[2],
    base_mac_addr[1],
    base_mac_addr[0],
    ret
  );
  */
  
  Serial.printf("ID Address = %02x%02x%02x%02x%02x%02x\n", 
    base_mac_addr[5],
    base_mac_addr[4],
    base_mac_addr[3],
    base_mac_addr[2],
    base_mac_addr[1],
    base_mac_addr[0],
    ret
  );



/*
  char macAddr[18];

  //macAddr = WiFi.macAddress();
  //macAddr.replace(":","");

  sprintf(macAddr, "%2X:%2X:%2X:%2X:%2X:%2X", ar[0], ar[1], ar[2], ar[3], ar[4], ar[5]);
  Serial.println(macAddr);

  macAddr[0] = '\0';
  for (byte i = 0; i < 6; ++i)
  {
    char buf[3];
    sprintf(buf, "%2X", ar[i]);
    strcat(macAddr, buf);
    if (i < 5) strcat(macAddr, ":");
  }
  macAddr[17] = '\0';
  Serial.println(macAddr);
  */
}

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