message: ESP32 DEFINE LED_BUILTIN
diff: //for LED status
  #include <Ticker.h>
  Ticker ticker;
  -int LED = BUILTIN_LED;
  +
  +#ifndef LED_BUILTIN
  +#define LED_BUILTIN 13 // ESP32 DOES NOT DEFINE LED_BUILTIN
  +#endif
  +
  +int LED = LED_BUILTIN;
  void tick()
  {
  