4.1.1 Xplained Pro Standard Extension Headers

The SAM D21 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 in Xplained Pro Standard Extension Header. All headers have a pitch of 2.54mm.

Table 4-1. Extension Header EXT1
Pin on EXT1SAM D21 pinFunctionShared functionality
1 [ID]--Communication line to ID chip on extension board.
2 [GND]--GND
3 [ADC(+)]PB00AIN[8]
4 [ADC(-)]PB01AIN[9]
5 [GPIO1]PB06GPIO
6 [GPIO2]PB07GPIO
7 [PWM(+)]PB02TC6/WO[0]
8 [PWM(-)]PB03TC6/WO[1]
9 [IRQ/GPIO]PB04EXTINT[4]
10 [SPI_SS_B/GPIO]PB05GPIO
11 [TWI_SDA]PA08SERCOM2 PAD[0] I²C SDAEXT2, EXT3, and EDBG
12 [TWI_SCL]PA09SERCOM2 PAD[1] I²C SCLEXT2, EXT3, and EDBG
13 [USART_RX]PB09SERCOM4 PAD[1] UART RX(1)
14 [USART_TX]PB08SERCOM4 PAD[0] UART TX(1)
15 [SPI_SS_A]PA05SERCOM0 PAD[1] SPI SS
16 [SPI_MOSI]PA06SERCOM0 PAD[2] SPI MOSI
17 [SPI_MISO]PA04SERCOM0 PAD[0] SPI MISO
18 [SPI_SCK]PA07SERCOM0 PAD[3] SPI SCK
19 [GND]--GND
20 [VCC]--VCC
Note:
  1. The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins on EXT1 and EXT2/3.
Table 4-2. Extension Header EXT2
Pin on EXT2SAM D21 pinFunctionShared functionality
1 [ID]--Communication line to ID chip on extension board.
2 [GND]--GND
3 [ADC(+)]PA10AIN[18]
4 [ADC(-)]PA11AIN[19]
5 [GPIO1]PA20GPIO
6 [GPIO2]PA21GPIO
7 [PWM(+)]PB12TC4/WO[0]
8 [PWM(-)]PB13TC4/WO[1]
9 [IRQ/GPIO]PB14EXTINT[14]
10 [SPI_SS_B/GPIO]PB15GPIO
11 [TWI_SDA]PA08SERCOM2 PAD[0] I²C SDAEXT1, EXT3, and EDBG
12 [TWI_SCL]PA09SERCOM2 PAD[1] I²C SCLEXT1, EXT3, and EDBG
13 [USART_RX]PB11SERCOM4 PAD[1] UART RX (1) EXT3
14 [USART_TX]PB10SERCOM4 PAD[0] UART TX(1) EXT3
15 [SPI_SS_A]PA17SERCOM1 PAD[1] SPI SS
16 [SPI_MOSI]PA18SERCOM1 PAD[2] SPI MOSI
17 [SPI_MISO]PA16SERCOM1 PAD[0] SPI MISO
18 [SPI_SCK]PA19SERCOM1 PAD[3] SPI SCK
19 [GND]--GND
20 [VCC]--VCC
Note:
  1. The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins on EXT1 and EXT2/3.
Table 4-3. Extension Header EXT3
Pin on EXT3SAM D21 pinFunctionShared functionality
1 [ID]--Communication line to ID chip on extension board.
2 [GND]--GND
3 [ADC(+)]PA02AIN[0]
4 [ADC(-)]PA03AIN[1](1)USB ID
5 [GPIO1]PB30GPIOOnboard LED0
6 [GPIO2]PA15GPIOOnboard SW0
7 [PWM(+)]PA12TCC2/WO[0]
8 [PWM(-)]PA13TCC2/WO[1](2)Serial Flash SS
9 [IRQ/GPIO]PA28EXTINT[8]
10 [SPI_SS_B/GPIO]PA27GPIO
11 [TWI_SDA]PA08SERCOM2 PAD[0] I²C SDAEXT1, EXT2, and EDBG
12 [TWI_SCL]PA09SERCOM2 PAD[1] I²C SCLEXT1, EXT2, and EDBG
13 [USART_RX]PB11SERCOM4 PAD[1] UART RX(3)
14 [USART_TX]PB10SERCOM4 PAD[0] UART TX(3)
15 [SPI_SS_A]PB17SERCOM5 PAD[1] SPI SS
16 [SPI_MOSI]PB22SERCOM5 PAD[2] SPI MOSIEDBG and Serial Flash
17 [SPI_MISO]PB16SERCOM5 PAD[0] SPI MISOEDBG and Serial Flash
18 [SPI_SCK]PB23SERCOM5 PAD[3] SPI SCKEDBG and Serial Flash
19 [GND]--GND
20 [VCC]--VCC
Note:
  1. PA03 can be used by USB ID or EXT3 PIN4 by changing the position of the jumper JS300 on J307.
  2. PA13 is by default connected to the Serial Flash SS line and is disconnected from the EXT3 PIN8. This can be changed by moving the 0Ω resistor R314 to R313.
  3. The SERCOM4 module is shared between EXT1, 2, and 3 UART's, but uses different pins on EXT1 and EXT2/3.