XIAO Pinout

Explore both sides of your XIAO board with an interactive pinout viewer. Search for pins, check their functions, and find wiring notes and alternate functions.

Logic level: 3.3V
5V tolerance: Not tolerant
3V3 budget: ≤ 200 mA
VBUS: 5V pin is USB VBUS in/out. Keep peripheral load under 500 mA.
Battery: No charger onboard; VIN pad on the back accepts 3.3–5V

#	Silk	Arduino	Chip	ADC	I²C	SPI	UART	PWM	Other	Note
1	L	LED_BUILTIN	PA17		SCL1 SERCOM1 PAD1			TCC	LED on SAMD21	User LED on SAMD21; SCL1 on SAMD21 Plus back header (D13).
2	P	P	VBUS
3	RST	RST	RESETN						RESET	Active-low reset. The board already pulls it up. Pulse it to ground to reboot.
4	D0	A0	PA02	AIN0 / A0				TCC	DAC0	Only PA02 (D0 / A0) has a true DAC. Other analog pins are ADC-only.
5	D1	A1	PA04	AIN4 / A1				TCC		ADC A1 (AIN4).
6	D2	A2	PA10	AIN10 / A2				TCC		Input voltage must not exceed 3.3V.
7	D3	A3	PA11	AIN11 / A3				TCC		Input voltage must not exceed 3.3V.
8	D4	SDA	PA08	AIN16 / A4	SDA SERCOM0/2 PAD0			TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
9	D5	SCL	PA09	AIN17 / A5	SCL SERCOM0/2 PAD1			TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
10	D6	TX	PB08	AIN2 / A6			TX SERCOM4 PAD0	TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
1	T	PIN_LED_TXL	PA19
2	R	PIN_LED_RXL	PA18
3	5V	5V	VBUS							This pad is USB VBUS. It sits near 5 V when USB is plugged in. Do not feed it back into a 3.3 V pin.
4	GND	GND	—							Common ground. Connect every module ground here so signals have a return path.
5	3V3	3V3	3V3_OUT							Regulated 3.3 V output. Current is limited; use a separate supply for hungry loads.
6	D10	MOSI	PA06	AIN6 / A10		MOSI SERCOM0 PAD2		TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
7	D9	MISO	PA05	AIN5 / A9		MISO SERCOM0 PAD1		TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
8	D8	SCK	PA07	AIN7 / A8		SCK SERCOM0 PAD3		TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
9	D7	RX	PB09	AIN3 / A7			RX SERCOM4 PAD1	TCC		SAMD21 routes I2C / SPI / UART through SERCOM pads. The Arduino core already assigns the XIAO defaults; changing them means picking the matching PAD.
1	SWCLK	SWCLK	PA30						SWCLK	SWD clock on PA30. Use with SWDIO to load firmware via a debug probe.
2	GND	GND	—							Ground next to the SWD pads. Tie the debugger ground here.
3	GND	GND	—							Ground next to VIN.
1	SWDIO	SWDIO	PA31						SWDIO	SWD data on PA31.
3	VIN	VIN	VBUS							VIN / VBUS follows USB 5 V. The SAMD21 I/O is 3.3 V only.