4.1.1 Xplained Pro Standard Extension Headers

The SAM D20 Xplained Pro headers EXT1, EXT2, and EXT3 offer access to the I/O of the microcontroller in order to expand the board e.g. by connecting extensions to the board. These headers all comply with the standard extension header specified inTable 3-4. All headers have a pitch of 2.54mm.

Table 4-1. Extension Header EXT1
Pin on EXT1	SAM D20 pin	Function	Shared functionality
1	-	-	Communication line to ID chip on extension board.
2	-	-	GND
3	PB00	AIN[8]
4	PB01	AIN[9]
5	PB06	GPIO
6	PB07	GPIO
7	PB02	TC6/WO[0]
8	PB03	TC6/WO[1]
9	PB04	EXTINT[4]
10	PB05	GPIO
11	PA08	SERCOM2 PAD[0] I²C SDA	EXT2, EXT3, and EDBG
12	PA09	SERCOM2 PAD[1] I²C SCL	EXT2, EXT3, and EDBG
13	PB09	SERCOM4 PAD[1] UART RX⁽¹⁾
14	PB08	SERCOM4 PAD[0] UART TX⁽¹⁾
15	PA05	SERCOM0 PAD[1] SPI SS
16	PA06	SERCOM0 PAD[2] SPI MOSI
17	PA04	SERCOM0 PAD[0] SPI MISO
18	PA07	SERCOM0 PAD[3] SPI SCK
19	-	-	GND
20	-	-	VCC

Note:

The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins.

Table 4-2. Extension Header EXT2
Pin on EXT2	SAM D20 pin	Function	Shared functionality
1	-	-	Communication line to ID chip on extension board.
2	-	-	GND
3	PA10	AIN[18]
4	PA11	AIN[19]
5	PA20	GPIO
6	PA21	GPIO
7	PA22	TC4/WO[0]
8	PA23	TC4/WO[1]
9	PB14	EXTINT[14]
10	PB15	GPIO
11	PA08	SERCOM2 PAD[0] I²C SDA	EXT1, EXT3, and EDBG
12	PA09	SERCOM2 PAD[1] I²C SCL	EXT1, EXT3, and EDBG
13	PB13	SERCOM4 PAD[1] UART RX⁽¹⁾
14	PB12	SERCOM4 PAD[0] UART TX⁽¹⁾
15	PA17	SERCOM1 PAD[1] SPI SS
16	PA18	SERCOM1 PAD[2] SPI MOSI
17	PA16	SERCOM1 PAD[0] SPI MISO
18	PA19	SERCOM1 PAD[3] SPI SCK
19	-	-	GND
20	-	-	VCC

Note:

The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins.

Table 4-3. Extension Header EXT3
Pin on EXT3	SAM D20 pin	Function	Shared functionality
1	-	-	Communication line to ID chip on extension board.
2	-	-	GND
3	PA02	AIN[0]
4	PA03	AIN[1]
5	PB30	GPIO
6	PA15	GPIO	Onboard SW0
7	PA12	TC2/WO[0]
8	PA13	TC2/WO[1]
9	PA28	EXTINT[8]
10	PA27	GPIO
11	PA08	SERCOM2 PAD[0] I²C SDA	EXT1, EXT2, and EDBG
12	PA09	SERCOM2 PAD[1] I²C SCL	EXT1, EXT2, and EDBG
13	PB11	SERCOM4 PAD[3] UART RX⁽¹⁾
14	PB10	SERCOM4 PAD[2] UART TX⁽¹⁾
15	PB17	SERCOM5 PAD[1] SPI SS
16	PB22	SERCOM5 PAD[2] SPI MOSI	EDBG
17	PB16	SERCOM5 PAD[0] SPI MISO	EDBG
18	PB23	SERCOM5 PAD[3] SPI SCK	EDBG
19	-	-	GND
20	-	-	VCC

Note:

The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins.