The Mega 2560 board has many facilities for speaking with a pc, An additional board, or other microcontrollers. The ATmega2560 presents four hardware UARTs for TTL (5V) serial conversation. An ATmega16U2 (ATmega 8U2 over the revision 1 and revision 2 boards) about the board channels one of those about USB https://ligamega2502468.educationalimpactblog.com/50233591/article-under-review