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Arduino UNO R3 pinout

Name: Arduino UNO R3 pinout with per-pin electrical limits
Creator: Xirkit

All 32 pins of the Arduino UNO R3, each mapped to the ATmega328P pad it routes to, with its functions and — for 23 pins — the electrical limits from the chip datasheet. Every number cites its page and table.

32 pins documented23 with electrical limits1 nc3 power out1 control3 ground2 power in22 gpiocomplete pinout

Pin table

Arduino UNO R3 pins, functions and electrical limits

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VIH/VIL: input thresholds · VOH/VOL: output levels · IOH/IOL: output current. Values apply to the chip pad each pin routes to, under the conditions cited in the source.
Pin	Position	Kind	Chip pad	Functions	VIH	VIL	VOH	VOL	IOH	IOL	5 V tolerant	Abs max	Source
NC	JANALOG · 1	nc		no_connect
IOREF	JANALOG · 2	power out		power_out									p.11
RESET	JANALOG · 3	control	PC6	PC6, RESET, PCINT14	4.5–5.5 V	-0.5–0.5 V					yes	-0.5–13 V	ATmega328P datasheet p.322 table 322_1
+3V3	JANALOG · 4	power out		power_out									p.11 table 11_1
+5V	JANALOG · 5	power out		power_out									p.11
GND	JANALOG · 6	ground		ground
GND	JANALOG · 7	ground		ground
VIN	JANALOG · 8	power in		power_in									p.6 table 6_2
A0	JANALOG · 9	gpio	PC0	D14, PC0, ADC0, PCINT8	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
A1	JANALOG · 10	gpio	PC1	D15, PC1, ADC1, PCINT9	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
A2	JANALOG · 11	gpio	PC2	D16, PC2, ADC2, PCINT10	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
A3	JANALOG · 12	gpio	PC3	D17, PC3, ADC3, PCINT11	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
A4/SDA	JANALOG · 13	gpio	PC4	D18, PC4, ADC4, SDA, PCINT12	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
A5/SCL	JANALOG · 14	gpio	PC5	D19, PC5, ADC5, SCL, PCINT13	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D0	JDIGITAL · 1	gpio	PD0	RX (Serial, to ATmega16U2), PD0, RXD, PCINT16	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D1	JDIGITAL · 2	gpio	PD1	TX (Serial, to ATmega16U2), PD1, TXD, PCINT17	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D2	JDIGITAL · 3	gpio	PD2	PD2, INT0, PCINT18	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D3	JDIGITAL · 4	gpio	PD3	PWM (~D3), PD3, PCINT19, OC2B, INT1	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D4	JDIGITAL · 5	gpio	PD4	PD4, PCINT20, XCK, T0	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D5	JDIGITAL · 6	gpio	PD5	PWM (~D5), PD5, PCINT21, OC0B, T1	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D6	JDIGITAL · 7	gpio	PD6	PWM (~D6), PD6, PCINT22, OC0A, AIN0	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D7	JDIGITAL · 8	gpio	PD7	PD7, PCINT23, AIN1	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D8	JDIGITAL · 9	gpio	PB0	PB0, PCINT0, CLKO, ICP1	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D9	JDIGITAL · 10	gpio	PB1	PWM (~D9), PB1, PCINT1, OC1A	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D10/SS	JDIGITAL · 11	gpio	PB2	PWM (~D10), PB2, PCINT2, SS, OC1B	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D11/MOSI	JDIGITAL · 12	gpio	PB3	PWM (~D11), PB3, PCINT3, OC2A, MOSI	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D12/MISO	JDIGITAL · 13	gpio	PB4	PB4, PCINT4, MISO	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
D13/SCK	JDIGITAL · 14	gpio	PB5	LED_BUILTIN, PB5, SCK, PCINT5	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
GND	JDIGITAL · 15	ground		ground
AREF	JDIGITAL · 16	power in	AREF	power_in									ATmega328P datasheet p.319 table 319_1
SDA	JDIGITAL · 17	gpio	PC4	PC4, ADC4, SDA, PCINT12	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1
SCL	JDIGITAL · 18	gpio	PC5	PC5, ADC5, SCL, PCINT13	3–5.5 V	-0.5–1.5 V	4.2–5 V	≤ 0.9 V	≤ 40 mA	≤ 40 mA	yes	-0.5–5.5 V	ATmega328P datasheet p.323 table 323_1

Answers from the record

Arduino UNO R3 pinout FAQ

What microcontroller does the Arduino UNO R3 use?

The Arduino UNO R3 is built around the ATmega328P, alongside ATmega16U2, SPX1117M3-L-5, LMV358LIST-A.9, ECS-160-20-4X-DU.

How many GPIO pins does the Arduino UNO R3 have?

20 GPIO pins are exposed. Xirkit documents 32 board pins, 23 of them with pin-level electrical limits.

Are the Arduino UNO R3 I/O pins 5 V tolerant?

Yes, the documented I/O pins are 5 V tolerant. Input-high threshold: 3–5.5 V.

How much current can a Arduino UNO R3 GPIO pin source?

Documented output-high current per pin: ≤ 40 mA. Values are traced to the chip datasheet; see the pinout table for per-pin limits and conditions.

What voltage powers the Arduino UNO R3?

Supply range 1–20 V. Power inputs: VIN (6–20 V), AREF (1–5 V).

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