Home Arduino arduino uno pinout, schematics and pin descriptions

arduino uno pinout, schematics and pin descriptions

by iainhendry

Arduino Uno Pinout




Microcontroller ATmega328P
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
PWM Digital I/O Pins 6
Analog Input Pins 6
DC Current per I/O Pin 20 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB (ATmega328P) of which 0.5 KB used by bootloader
SRAM 2 KB (ATmega328P)
EEPROM 1 KB (ATmega328P)
Clock Speed 16 MHz
Length 68.6 mm
Width 53.4 mm
Weight 25 g


Arduino Uno Pinout

Arduino UNO Pinout Description


Category Name Details
Power Vin, 3.3V, 5V, GND Vin: Input voltage to the Arduino when using an external power source.

5V: Regulated power supply used to power microcontroller and other components on the board.

3.3V:  supply generated by on-board voltage regulator. Maximum current draw is 50mA.

GND: ground pins.

Reset Reset If you make this pin LOW, it will reset the microcontroller
Analog Pins A0 – A5 Used to provide analog input in the range of 0-5V
Input/Output Pins Digital Pins 0 – 13 Can be used as input or output pins.
Serial 0(Rx), 1(Tx) Rx and Tx pins are used to receive and transmit TTL serial data.
External Interrupts 2, 3 These two pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value.
PWM 3, 5, 6, 9, 11 These pins provide an 8-bit PWM output using the analogWrite() function.
SPI 10 (SS), 11 (MOSI), 12 (MISO) and 13 (SCK) Used for SPI communication.
Inbuilt LED 13 This pin is connected to an on board LED, when pin 13 is HIGH the LED is switched on and when pin 13 is LOW, its switched off.
TWI A4 (SDA), A5 (SCA) Used for TWI/I2C communication. You can use the Wire library to access this functionality
AREF AREF This is used to provide reference voltage for analog inputs. You can use the  analogReference() function.


The 14 digital input/output pins can be used as input or output pins by using the pinMode(), digitalRead() and digitalWrite() functions in the Arduino IDE. Each pin operates at 5V and can provide or receive a maximum of 40mA current, and each pin also has an internal pull-up resistor of 20-50 KOhms which are disconnected by default.


The Arduino Uno has a number of facilities for communicating with a computer, another Arduino board, or other microcontrollers. The ATmega328 provides UART TTL  serial communication, which is available on digital pins 0 and 1. An ATmega16U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer.

The 16U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. The Arduino IDE includes a serial monitor which allows simple textual data to be sent to and from the board.

The RX and TX LEDs on the board will flash when data is being transmitted via the USB-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).


Pin Mapping

Atmega pinmapping

Atmega pinmapping


Arduino Uno schematic


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