4.2.1 Xplained Pro Extension Headers

The SAM C21 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 EXT1SAM C21 pinFunctionShared functionality
1 [ID]--Communication line to the ID chip on an extension board.
2 [GND]--Ground.
3 [ADC(+)]PB09INP1Shield
4 [ADC(-)]PB08INN1Shield
5 [GPIO1]PA20GPIOShield
6 [GPIO2]PA21GPIOShield
7 [PWM(+)]PB12TC0/WO0Shield and EDBG GPIO0
8 [PWM(-)]PB13TC0/WO1Shield
9 [IRQ/GPIO]PB14IRQ14/GPIO-
10 [SPI_SS_B/GPIO]PB15GPIO-
11 [TWI_SDA]PA12SERCOM2 PAD[0] I2C SDAEXT2, EXT3, Shield, Crypto Device, and EDBG I2C
12 [TWI_SCL]PA13SERCOM2 PAD[1] I2C SCLEXT2, EXT3, Shield, Crypto Device, and EDBG I2C
13 [USART_RX]PA23SERCOM3 PAD[1] UART RXEXT2, EXT3, and Shield
14 [USART_TX]PA22SERCOM3 PAD[0] UART TXEXT2, EXT3, and Shield
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]--Ground.
20 [VCC]--Power for extension board.
Table 4-2. Extension Header EXT2
Pin on EXT2SAM C21 pinFunctionShared functionality
1 [ID]--Communication line to the ID chip on an extension board.
2 [GND]--Ground.
3 [ADC(+)]PA08AIN10Shield
4 [ADC(-)]PA09AIN11Shield
5 [GPIO1]PA10GPIO-
6 [GPIO2]PA11GPIO-
7 [PWM(+)]PB30TCC0/WO0Shield
8 [PWM(-)]PB31TCC0/WO1Shield
9 [IRQ/GPIO]PB16IRQ0/GPIOEDBG GPIO1
10 [SPI_SS_B/GPIO]PB17GPIOEDBG GPIO2
11 [TWI_SDA]PA12SERCOM2 PAD[0] I2C SDAEXT1, EXT3, Shield, Crypto Device, and EDBG I2C
12 [TWI_SCL]PA13SERCOM2 PAD[1] I2C SCLEXT1, EXT3, Shield, Crypto Device, and EDBG I2C
13 [USART_RX]PA23SERCOM3 PAD[1] UART RXEXT1, EXT3, and Shield
14 [USART_TX]PA22SERCOM3 PAD[0] UART TXEXT1, EXT3, and Shield
15 [SPI_SS_A]PB03SERCOM5 PAD[1] SPI SS
16 [SPI_MOSI]PB00SERCOM5 PAD[2] SPI MOSIEXT3, Shield, Shield(2), and EDBG SPI
17 [SPI_MISO]PB02SERCOM5 PAD[0] SPI MISOEXT3, Shield, Shield(2), and EDBG SPI
18 [SPI_SCK]PB01SERCOM5 PAD[3] SPI SCKEXT3, Shield, Shield(2), and EDBG SPI
19 [GND]--Ground.
20 [VCC]--Power for extension board.
Table 4-3. Extension Header EXT3
Pin on EXT3SAM C21 pinFunctionShared functionality
1 [ID]--Communication line to the ID chip on an extension board.
2 [GND]--Ground.
3 [ADC(+)]PB07AIN9/INP2Shield
4 [ADC(-)]PB06AIN8/INN2Shield
5 [GPIO1]PB04GPIOShield
6 [GPIO2]PB05GPIOShield
7 [PWM(+)]PA14TC4/WO0Crystal footprint
8 [PWM(-)]PA15TC4/WO1User LED and Crystal footprint
9 [IRQ/GPIO]PA28IRQ8/GPIOUser Button and EDBG GPIO3
10 [SPI_SS_B/GPIO]PA27GPIOShield
11 [TWI_SDA]PA12SERCOM2 PAD[0] I2C SDAEXT1, EXT2, Shield, Crypto Device, and EDBG I2C
12 [TWI_SCL]PA13SERCOM2 PAD[1] I2C SCLEXT1, EXT2, Shield, Crypto Device, and EDBG I2C
13 [USART_RX]PA23SERCOM3 PAD[1] UART RXEXT1, EXT2, and Shield
14 [USART_TX]PA22SERCOM3 PAD[0] UART TXEXT1, EXT2, and Shield
15 [SPI_SS_A]PA02GPIODAC Header
16 [SPI_MOSI]PB00SERCOM5 PAD[2] SPI MOSIEXT2, Shield, Shield(2), and EDBG SPI
17 [SPI_MISO]PB02SERCOM5 PAD[0] SPI MISOEXT2, Shield, Shield(2), and EDBG SPI
18 [SPI_SCK]PB01SERCOM5 PAD[3] SPI SCKEXT2, Shield, Shield(2), and EDBG SPI
19 [GND]--Ground.
20 [VCC]--Power for extension board.