Look at the schematic pdf: JP2 is 4 signals: 16U2 port PB4..PB7
BTW: the 6pin header block above is obviously the one labelled ICSP2 in the schematic, can be used to program the 16U2
Look at the schematic pdf: JP2 is 4 signals: 16U2 port PB4..PB7
BTW: the 6pin header block above is obviously the one labelled ICSP2 in the schematic, can be used to program the 16U2