The Arduino Uno is the standard board of the Arduino which was introduced at the New York Maker Faire in September 2010.

Arduino Uno. Source:

Arduino Uno Specifications

DescriptionDetailed data
Power supply7-12 VDC
Operating voltage5 VDC and 3.3 VDC (internally generated by voltage regulator)
Digital inputs/outputs14 (6 of them as PWM outputs)
Analog inputs6
Current per digital pin40 mA DC
Flash memory32 KB (ATmega328), where 0,5 KB are occupied by the bootloader
SRAM2 KB (ATmega328)  
EEPROM1 KB (ATmega328)
Clock frequency16 MHz
USB interfaceyes
Reset switchyes

Arduino Uno Pinout

Arduino Uno Pinout. Source: pighixxx

What type of connector does an Arduino Uno contains ?

On the Arduino Uno the following connectors are standard:

  • USB socket: The USB port (type B) is used for programming via the development environment and for communication with the connected computer. At the same time the board can be powered via the USB port.
  • Socket for external power supply: The Arduino board can be supplied with an external power supply or battery via a 2.1 mm socket. The power supply via the USB port is automatically deactivated. A particular advantage is the higher power that can be drawn from the external supply voltage, for example to supply actuators and sensors. In case of a short-circuit, it is not the USB port of the connected computer that is loaded, but the overload protection of the external power supply.
  • Connector strips for digital inputs and outputs: Single-row connector sockets that can be plugged into the extension boards (shields) or connector strips. All existing ports and interfaces are available via these connector strips.
  • ICSP: The pin row for the ICSP (In-Circuit Serial Programming) allows programming of sketches (programs) without bootloader by means of an external programming device.

Arduino Ports

A “port” is a connector pin of the microcontroller that can be programmed as input or output.
The Arduino inputs and outputs are the interfaces to the physical world to read environmental data. Input ports read e.g. temperatures, humidity, distance from an infrared sensor, or signals from a limit switch, etc. Output ports are used to control e.g. lamps, relays, or motors, etc.

This article describes the Arduino digital port and this article describes the capabilities of the Arduino analog pins. The Arduino Uno has 14 digital ports and 6 analog ports.

Individual ports have additional special tasks like the transmitter signal (port D1) or receiver signal (port D0) of the serial interface or the pulse width modulation (PWM).

Using Arduino expansion board (Arduino shields) the number of ports or their functionality can be extended. You should note that that the shields occupy ports that can no longer be used by the applications on the extensions. For example, the Ethernet Shield reserves port 10 to 13 for SPI communication.