A classic serial UART ( not midi )

[LoicLac]

Hello , I'd like to connect NeoTrellis via a SERIAL UART to communicate with another arduino board . a classic serial Tx Rx ... I understand in the documentation that there is a port with sda and scl on a STEMMA output format ( that i used very well with midi ) . How to enable it in the arduino IDE ? A place to start digging ? some tips ? Thank you ! Loic L