4.3.1 Target Digital I/O

The J200 and J201 headers provide access to the ATmega328P digital I/O pins.

Table 4-1. J200 Digital I/O High Byte Header
J200 Pin	ATmega328P Pin	Function
1	PB0
2	PB1
3	PB2	SS, SPI Bus Master Slave select
4	PB3	MOSI, SPI Bus Master Output/Slave Input
5	PB4	MISO, SPI Bus Master Input/Slave Output
6	PB5	SCK, SPI Bus Master Clock Input
7	GND
8	AREF
9	PC4	SDA, 2-wire Serial Bus Data Input/Output Line. Shared with ADC4.
10	PC5	SCL, 2-wire Serial Bus Clock Line. Shared with ADC5.