Arduino Uno R3 (ATmega328P)
Arduino Uno R3 · ATmega328P 16 MHz, 5 V logic · 32 KB flash (0.5 KB bootloader), 2 KB SRAM, 1 KB EEPROM · 14 digital I/O + 6 analog in · PWM on 3, 5, 6, 9, 10, 11 · VIN 7–12 V (6–20 V limits) · 20 mA per pin (40 mA absolute max) · ATmega16U2 USB-serial
Try it on the benchThe lab drops it on an empty bench and opens its datasheet card.
Typical part: Arduino Uno R3 (A000066) · ATmega328P + ATmega16U2
Pins
- SCL
- SDA
- AREF
- GND
- D13
- D12
- D11 ~
- D10 ~
- D9 ~
- D8
- D7
- D6 ~
- D5 ~
- D4
- D3 ~ (INT1)
- D2 (INT0)
- D1 TX→
- D0 RX←
- IOREF
- RESET
- 3.3V
- 5V
- GND
- GND
- VIN
- A0
- A1
- A2
- A3
- A4 (SDA)
- A5 (SCL)
- USB-B port
- DC jack centre (+)
- DC jack sleeve (−)
Ratings and limits
| Operating voltage | 5 V |
|---|---|
| Input voltage | 7–12 V recommended, 6–20 V limits (VIN or the 2.1 mm jack) |
| USB | 5 V, protected by a 500 mA resettable polyfuse |
| Current per I/O pin | 20 mA recommended, 40 mA absolute maximum |
| Total through VCC/GND | 200 mA |
| 3.3 V pin | 50 mA |
| Flash / SRAM / EEPROM | 32 KB (0.5 KB bootloader) / 2 KB / 1 KB |
| Clock | 16 MHz |
| PWM | pins 3, 5, 6, 9, 10, 11 (490 Hz; 980 Hz on 5 and 6) |
| ADC | 6 inputs, 10-bit (0–1023) |
| Interrupts | pins 2 and 3 |
How to use it
Feed 7–12 V into VIN or the barrel jack; the onboard regulator makes 5 V, but it gets hot fast: at 12 V it can only supply a few hundred milliamps before it shuts down. Never put more than 5 V on the 5V pin. Drive motors, relays and long LED strips through a transistor or MOSFET from their own supply, never straight from a pin.
Lessons and builds that use it
- Arduino Uno: upload your first sketch
- Reading a button: floating inputs and INPUT_PULLUP
- analogRead and PWM: a pot dims an LED
- Powering an Arduino: USB, VIN and the regulator
- Traffic light with a pedestrian button (build)
- Reaction-time game (build)
- Electronic dice (build)
- Simon memory game (build)
- Ultrasonic parking sensor (build)
- Keypad door lock (build)