4.2.1 Xplained Pro Standard Extension Headers

The ATtiny817 Xplained Pro headers EXT1 and EXT3 offer access to the I/O of the microcontroller to expand the board, e.g., by connecting extensions to the board. These headers are based on the standard extension header specified in the table below. The headers have a pitch of 2.54 mm.

Table 4-1. Extension Header EXT1
EXT1 Pin	ATtiny817 Pin	Function	Shared Functionality
1 [ID]	-	-	Communication line to the ID chip on an extension board
2 [GND]	-	-	Ground
3 [ADC(+)]	PA6	AIN6	QTouch Button 1
4 [ADC(-)]	PA7	AIN7	QTouch Button 2
5 [GPIO1]	PB7	GPIO	-
6 [GPIO2]	PB4	GPIO	LED0
7 [PWM(+)]	PB0	TC/W0	-
8 [PWM(-)]	PB1	TC/W1	-
9 [IRQ/GPIO]	PA5	IRQ/GPIO	-
10 [SPI_SS_B/GPIO]	PA4	GPIO	-
11 [I²C_SDA]	PA1	I²C SDA	EXT3 and EDBG I²C
12 [I²C_SCL]	PA2	I²C SCL	EXT3 and EDBG I²C
13 [USART_RX]	PB3	UART RX	EXT3, EDBG CDC, and Crystal ⁽¹⁾
14 [USART_TX]	PB2	UART TX	EXT3, EDBG CDC, and Crystal ⁽¹⁾
15 [SPI_SS_A]	PC3	SPI SS	-
16 [SPI_MOSI]	PC2	SPI MOSI	EXT3 and EDBG SPI
17 [SPI_MISO]	PC1	SPI MISO	EXT3 and EDBG SPI
18 [SPI_SCK]	PC0	SPI SCK	EXT3 and EDBG SPI
19 [GND]	-	-	Ground
20 [VCC]	-	-	Power for extension board

1) Not connected by default, see Connecting the 32.768 kHz Crystal for more information.

Note: Signal functions in italic use alternative pin location. These have to be configured in the PORTMUX register of the device.

Table 4-2. Extension Header EXT3
EXT3 Pin	ATtiny817 Pin	Function	Shared Functionality
1 [ID]	-	-	Communication line to the ID chip on an extension board
2 [GND]	-	-	Ground
3 [ADC(+)]	-	-
4 [ADC(-)]	-	-
5 [GPIO1]	PC5	GPIO	SW1 and UPDI debug connector
6 [GPIO2]	-	-
7 [PWM(+)]	-	-
8 [PWM(-)]	-	-
9 [IRQ/GPIO]	PB6	IRQ/GPIO	EDBG DGI
10 [SPI_SS_B/GPIO]	PB5	GPIO	SW0 and EDBG DGI
11 [I²C_SDA]	PA1	I²C SDA	EXT1 and EDBG I²C
12 [I²C_SCL]	PA2	I²C SCL	EXT1 and EDBG I²C
13 [USART_RX]	PB3	UART RX	EXT1, EDBG CDC, and Crystal ⁽¹⁾
14 [USART_TX]	PB2	UART TX	EXT1, EDBG CDC, and Crystal ⁽¹⁾
15 [SPI_SS_A]	PA3	GPIO / SPI_SS	-
16 [SPI_MOSI]	PC2	SPI MOSI	EXT1 and EDBG SPI
17 [SPI_MISO]	PC1	SPI MISO	EXT1 and EDBG SPI
18 [SPI_SCK]	PC0	SPI SCK	EXT1 and EDBG SPI
19 [GND]	-	-	Ground
20 [VCC]	-	-	Power for extension board

1) Not connected by default, see Connecting the 32.768 kHz Crystal for more information.

Note: Signal functions in italic use alternative pin location. These have to be configured in the PORTMUX register of the device.