The Mega 2560 board has a variety of facilities for communicating with a computer, A further board, or other microcontrollers. The ATmega2560 gives 4 components UARTs for TTL (5V) serial interaction. An ATmega16U2 (ATmega 8U2 around the revision 1 and revision two boards) over the board channels one of those https://ligamega2503579.loginblogin.com/34383705/fascination-about-ligamega25