4.2.1 Xplained Pro Extension Headers

The SAMC21N Xplained Pro headers EXT1, EXT2, and EXT3 offers access to the I/O of the microcontroller in order to expand the board e.g. by connecting extensions to the board. These headers are based on the standard extension header specified in Xplained Pro Standard Extension Header. The headers have a pitch of 2.54mm.

Table 4-1. Extension Header EXT1
Pin on EXT1	SAMC21N pin	Function	Shared functionality
1 [ID]	-	-	Communication line to the ID chip on an extension board.
2 [GND]	-	-	Ground.
3 [ADC(+)]	PB09	ADC0_AIN3 or SDADC_INP[1] or Y[15]	Shield
4 [ADC(-)]	PB08	ADC0_AIN2 or SDADC_INN[1] or Y[14]	Shield
5 [GPIO1]	PA10	SERCOM2 PAD[2] UART RTS or X[2]/Y[18]	-
6 [GPIO2]	PA11	SERCOM2 PAD[3] UART CTS or X[3]/Y[19]	-
7 [PWM(+)]	PB12	TC4/WO[0] or X[12]/Y[28]	EDBG GPIO0
8 [PWM(-)]	PB13	TC4/WO[1] or X[13]/Y[29]	-
9 [IRQ/GPIO]	PA22	IRQ6 or TC4/WO[0] or TCC1/WO[0] or X[10]/Y[26]	EDBG GPIO1
10 [SPI_SS_B/GPIO]	PA23	GPIO or TC4/WO[1] or TCC1/WO[1] or X[11]/Y[27]	-
11 [TWI_SDA]	PB16	SERCOM5 PAD[0] I²C SDA	-
12 [TWI_SCL]	PB17	SERCOM5 PAD[1] I²C SCL	-
13 [USART_RX]	PA13	SERCOM2 PAD[1] UART RX	-
14 [USART_TX]	PA12	SERCOM2 PAD[0] UART TX	-
15 [SPI_SS_A]	PC28	SERCOM1 PAD[1] SPI SS	-
16 [SPI_MOSI]	PA18	SERCOM1 PAD[2] SPI MOSI or X[6]/Y[22]	-
17 [SPI_MISO]	PC27	SERCOM1 PAD[0] SPI MISO	-
18 [SPI_SCK]	PA19	SERCOM1 PAD[3] SPI SCK or X[7]/Y[23]	-
19 [GND]	-	-	Ground.
20 [VCC]	-	-	Power for extension board.

Table 4-2. Extension Header EXT2
Pin on EXT2	SAMC21N pin	Function	Shared functionality
1 [ID]	-	-	Communication line to the ID chip on an extension board.
2 [GND]	-	-	Ground.
3 [ADC(+)]	PA08	ADC1_AIN[10] or X[0]/Y[16]	-
4 [ADC(-)]	PA09	ADC1_AIN[11] or X[1]/Y[17]	-
5 [GPIO1]	PA20	SERCOM3 PAD[2] UART RTS or X[8]/Y[24]	-
6 [GPIO2]	PA21	SERCOM3 PAD[3] UART CTS or X[9]/Y[25]	-
7 [PWM(+)]	PB30	TC0/WO[0]	Shield
8 [PWM(-)]	PB31	TC0/WO[1]	Shield
9 [IRQ/GPIO]	PC24	IRQ0/GPIO	EDBG GPIO2
10 [SPI_SS_B/GPIO]	PC25	GPIO	-
11 [TWI_SDA]	PA16	SERCOM1 PAD[0] I²C SDA	EXT3, Shield, EDBG I²C and Crypto Device
12 [TWI_SCL]	PA17	SERCOM1 PAD[1] I²C SCL	EXT3, Shield, EDBG I²C and Crypto Device
13 [USART_RX]	PB21	SERCOM3 PAD[1] UART RX	-
14 [USART_TX]	PB20	SERCOM3 PAD[0] UART TX	-
15 [SPI_SS_A]	PB03	SERCOM5 PAD[1] SPI SS or Y[9]	-
16 [SPI_MOSI]	PB00	SERCOM5 PAD[2] SPI MOSI or Y[6]	-
17 [SPI_MISO]	PB02	SERCOM5 PAD[0] SPI MISO or Y[8]	-
18 [SPI_SCK]	PB01	SERCOM5 PAD[3] SPI SCK or Y[7]	-
19 [GND]	-	-	Ground.
20 [VCC]	-	-	Power for extension board.

Table 4-3. Extension Header EXT3
Pin on EXT3	SAMC21N pin	Function	Shared functionality
1 [ID]	-	-	Communication line to the ID chip on an extension board.
2 [GND]	-	-	Ground.
3 [ADC(+)]	PB07	ADC1_AIN[9] or SDADC_INP[2] or Y[13]	-
4 [ADC(-)]	PB06	ADC1_AIN[8] or SDADC_INN[2] or Y[12]	-
5 [GPIO1]	PC18	SERCOM6 PAD[2] UART RTS	-
6 [GPIO2]	PC19	SERCOM6 PAD[3] UART CTS	-
7 [PWM(+)]	PB22	TCC1/WO[2]	-
8 [PWM(-)]	PB23	TCC1/WO[3]	-
9 [IRQ/GPIO]	PA28	IRQ8/GPIO	EDBG GPIO3
10 [SPI_SS_B/GPIO]	PA27	GPIO	-
11 [TWI_SDA]	PA16	SERCOM1 PAD[0] I²C SDA	EXT2, Shield, EDBG I²C and Crypto Device
12 [TWI_SCL]	PA17	SERCOM1 PAD[1] I²C SCL	EXT2, Shield, EDBG I²C and Crypto Device
13 [USART_RX]	PC17	SERCOM6 PAD[1] UART RX	-
14 [USART_TX]	PC16	SERCOM6 PAD[0] UART TX	-
15 [SPI_SS_A]	PC13	SERCOM7 PAD[1] SPI SS	-
16 [SPI_MOSI]	PC14	SERCOM7 PAD[2] SPI MOSI	Shield, Shield(2), and EDBG SPI
17 [SPI_MISO]	PC12	SERCOM7 PAD[0] SPI MISO	Shield, Shield(2), and EDBG SPI
18 [SPI_SCK]	PC11	SERCOM7 PAD[3] SPI SCK	Shield, Shield(2), and EDBG SPI
19 [GND]	-	-	Ground.
20 [VCC]	-	-	Power for extension board.