Arduino Uno R3 Specifications/Functions

In this article, we will explain in detail the specifications and functions of Arduino Uno R3(Arduino Uno).

Arduino Uno is the most representative and basic edition of the more than 20 editions.

Arduino Uno Specifications

Tech Specs	Arduino Uno
Board Size	74.9×53.3mm
Microcontroller/ Clock Speed	ATmega328P/ 16MHz
SRAM (Main Memory)	2kB
Flash Memory	32kB
EEPROM	1kB
Operating Voltage	+5V
Input Voltage (recommended)	+7～+12V
Output Voltage	+5V, +3.3V
Digital I/O Pins	20
PWM Digital I/O Pins	6
Analog Input Pins	6
Analog Output Pins (DAC)	-
Rated Current per Pin	40mA/Pin
Program Writing Pins	USB Type-B ICSP
Interface	UART I2C SPI

For the specifications of Arduino boards other than Arduino Uno, please refer to the following article.

Arduino Uno Functions

Arduino Uno Appearance

Socket Header Placement(Pin Header Placement)/LED Placement

↑Click to enlarge.

①Microcontroller(Microcomputer)

The microcontroller of the Arduino Uno uses "ATmega328P" from Microchip Technology(USA).

A microcontroller is a very important component in controlling electronic devices that correspond to the human "brain".

In addition, various memories such as SRAM, Flash memory, and EEPROM are also built into the microcontroller.

②USB Port

By connecting the Arduino Uno to the USB port of your PC with a USB cable, you can communicate between the Arduino Uno and your PC.

Programs (sketches) created on the PC can be written to the Arduino Uno, and the Arduino Uno can be controlled from the PC via serial communication.

The Arduino Uno can also be powered via USB instead of the power jack.

③Power Jack

You can connect an AC adapter(outer diameter 5.5mm, inner diameter 2.1mm) to power the Arduino Uno.

④Reset Button

You can restart the Arduino Uno by pressing the reset button. Use this when you want to restart the program from the beginning or when the Arduino Uno behaves strangely.

⑤I/O Port・Power

Digital I/O・PWM

Digital I/O・PWM	Explanation
D0-D19	Digital input/output(0-19) HIGH(+5V)/LOW(0V)
PWM	0 to +5V analog output Analog output by switching between 0V and +5V at high speed

PWM and serial communication are shared with digital I/O. You can specify which one to use in the program.

Analog Input

Analog Input	Explanation
A0-A5	Analog input(0-5) 10-bit A/D converter(1step change every 4.8mV)

Communication

Communication		Explanation
UART (Serial communication)	TX	Serial data transmission
〃	RX	Serial data reception
I2C	SCL	Serial clock
〃	SDA	Serial data transmission/reception
SPI	SS	Select device to control
〃	SCK	Serial clock
〃	MOSI	Master ⇒ Slave data transfer
〃	MISO	Slave ⇒ Master data transfer

Power

Power	Explanation
Vin	The voltage of "③Power jack" is output, Power can be supplied from "Vin" without using the power jack.
GND	Ground/Reference point
+5V	+5V voltage output
+3.3V	+3.3V voltage output

Other

Other	Explanation
GND	Ground/Reference point
AREF	Analog input reference voltage (0 to +5V input), Not normally used
RESET	Reset (Same function as "④Reset Button")
IOREF	+5V voltage output

⑥LED

LED	Explanation
ON	Lights up when the Arduino Uno is powered
TX	Blinks when sending via serial communication
RX	Blinks when receiving via serial communication
L	Connect to digital I/O No.13

Arduino Uno has 4 LEDs(chip parts). The "L" of LED is connected to the 13th digital I/O, and can be lighted up by setting the 13th pin to HIGH(5V) in the program.

⑦ICSP

Arduino Uno has two ICSP terminals, for "ATmega328P" and "ATmega16U2".

For ATmega328P

By connecting an ICSP-compatible writer(program writing device), you can write programs(sketches) directly to the "ATmega328P", which is an Arduino Uno microcontroller(microcomputer).

However, since you can usually write programs(sketches) via the USB port, I think that it is rarely used for writing purposes.

In addition, it can also be used as an SPI terminal.

For ATmega16U2

By connecting an ICSP-compatible writer(program writing device), you can write sketches(programs) directly to the "ATmega16U2", which is USB-serial conversion IC of Arduino Uno.

Therefore, you can create a device for USB, but it is rarely used because it cannot be written by the Arduino IDE.

How to get technical data for Arduino Uno

Various technical materials of Arduino Uno can be obtained from the official Arduino website.