Comunicar en serie dos Arduinos esta explicado en todo la web
Google: 2 Arduinos serial
https://www.hackster.io/harshmangukiya/serial-communication-between-two-arduino-boards-d423e9
Google: Arduino Esp8266 serial
http://www.martyncurrey.com/arduino-to-esp8266-serial-commincation/
https://forum.arduino.cc/index.php?topic=462829.0
