4.1.1 Xplained Pro Standard Extension Headers

The ATMEGA256RFR2 Xplained Pro headers EXT1, EXT2, EXT3, EXT4, and EXT5 offers access to the I/O of the microcontroller in order to expand the board e.g. by connecting extension modules to the board. These headers all comply with the standard extension header specified in Table 3-4. All headers have a pitch of 2.54mm.

Table 4-1. Extension Header EXT1
Pin on EXT1	ATmega256RFR2 pin	Function	Shared functionality
1		Communication line to ID chip on extension board
2		GND
3	PF0	ADC0
4	PF1	ADC1
5	PE2	GPIO
6	PE3	GPIO
7	PB5	OC1A	EXT4 header
8	PB6	OC1B
9	PE5	GPIO / INT5	EXT4 header
10	PD5	GPIO / SPI chip select B	EXT4 header
11	PD1	TWI SDA	All EXT headers
12	PD0	TWI SCL	All EXT headers
13	PE0	UART0 RXD	All EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
14	PE1	UART0 TXD	All EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
15	PG0	GPIO / SPI chip select A	EXT4 header
16	PB2	SPI MOSI	All EXT headers
17	PB3	SPI MISO	All EXT headers
18	PB1	SPI SCK	All EXT headers
19		GND
20		VCC

Table 4-2. Extension Header EXT2
Pin on EXT2	ATmega256RFR2 pin	Function	Shared functionality
1		Communication line to ID chip on extension board
2		GND
3
4
5
6
7
8
9	PE6	GPIO / INT6	EXT5 header
10	PD6	GPIO / SPI chip select B	EXT5 header
11	PD1	TWI SDA	All other EXT headers
12	PD0	TWI SCL	All other EXT headers
13	PE0⁽¹⁾	UART0 RXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
14	PE1⁽¹⁾	UART0 TXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
15	PD4	GPIO / SPI chip select A	EXT5 header
16	PB2	SPI MOSI	All other EXT headers
17	PB3	SPI MISO	All other EXT headers
18	PB1	SPI SCK	All other EXT headers
19		GND
20		VCC

Note:

Connected through cut-strap.

Table 4-3. Extension Header EXT3
Pin on EXT3	ATmega256RFR2 pin	Function	Shared functionality
1		Communication line to ID chip on extension board
2		GND
3	PF3	GPIO
4	PG5	GPIO
5	PB7	GPIO
6
7
8
9	PE7	GPIO / INT7
10	PD7	GPIO / SPI chip select B
11	PD1	TWI SDA	All other EXT headers
12	PD0	TWI SCL	All other EXT headers
13	PE0⁽¹⁾	UART0 RXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
14	PE1⁽¹⁾	UART0 TXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
15	PG2	GPIO / SPI chip select A
16	PB2	SPI MOSI	All other EXT headers
17	PB3	SPI MISO	All other EXT headers
18	PB1	SPI SCK	All other EXT headers
19		GND
20		VCC

Note:

Connected through cut-strap.

Table 4-4. Extension Header EXT4
Pin on EXT4	ATmega256RFR2 pin	Function	Shared functionality
1		Communication line to ID chip on extension board
2		GND
3
4
5
6
7	PB5	OC1A	EXT1 header
8
9	PE5	GPIO / INT5	EXT1 header
10	PG0	GPIO / SPI chip select B	EXT1 header
11	PD1	TWI SDA	All other EXT headers
12	PD0	TWI SCL	All other EXT headers
13	PE0	UART0 RXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
14	PE1	UART0 TXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
15	PD5	GPIO / SPI chip select A	EXT1 header
16	PB2	SPI MOSI	All other EXT headers
17	PB3	SPI MISO	All other EXT headers
18	PB1	SPI SCK	All other EXT headers
19		GND
20		VCC

Table 4-5. Extension Header EXT5
Pin on EXT5	ATmega256RFR2 pin	Function	Shared functionality
1		Communication line to ID chip on extension board
2		GND
3
4
5
6
7
8
9	PE6	GPIO / INT6	EXT2 header
10	PD4	GPIO / SPI chip select B	EXT2 header
11	PD1	TWI SDA	All other EXT headers
12	PD0	TWI SCL	All other EXT headers
13	PE0⁽¹⁾	UART0 RXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
14	PE1⁽¹⁾	UART0 TXD	All other EXT headers. EXT2, EXT3 and EXT5 connected through cut-strap.
15	PD6	GPIO / SPI chip select A	EXT2 header
16	PB2	SPI MOSI	All other EXT headers
17	PB3	SPI MISO	All other EXT headers
18	PB1	SPI SCK	All other EXT headers
19		GND
20		VCC

Note:

Connected through cut-strap.

ATmega256RFR2 Xplained Pro

4.1.1 Xplained Pro Standard Extension Headers