Arduino Nano. The Arduino Nano is an open-source breadboard-friendly microcontroller board based on the Microchip ATmega328P microcontroller (MCU) and developed by Arduino.cc and initially released in 2008. It offers the same connectivity and specs of the Arduino Uno board in a smaller form factor.

The Arduino Nano is equipped with 30 male I/O headers, in a DIP-30-like configuration, which can be programmed using the Arduino Software integrated development environment (IDE), which is common to all Arduino boards and running both online and offline. The board can be powered through a type-B mini-USB cable or from a 9 V battery.

History
In 2008, the Arduino Nano was released.

In 2019, Arduino released the Arduino Nano Every, a pin-equivalent evolution of the Nano. It features a ATmega4809 microcontroller (MCU) with three times the RAM.

Technical specifications  

 Microcontroller: Microchip ATmega328P
 Operating voltage: 5 volts
 Input voltage: 5 to 20 volts
 Digital I/O pins: 14 (6 optional PWM outputs)
 Analog input pins: 8
 DC per I/O pin: 40 mA
 DC for 3.3 V pin: 50 mA
 Flash memory: 32 KB, of which 2 KB is used by bootloader
 SRAM: 2 KB
 EEPROM: 1 KB
 Clock speed: 16 MHz
 Length: 45 mm
 Width: 18 mm
 Mass: 7 g
 USB: Mini-USB Type-B 
 ICSP Header: Yes
 DC Power Jack: No

Communication 
The Arduino Nano has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL serial (5V) communication, which is available on digital pins 0 (RX) and 1 (TX). 

An FTDI FT232RL on the board channels this serial communication over USB and the FTDI drivers (included with the Arduino firmware) provide a virtual com port to software on the computer. The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the Arduino board. The RX and TX LEDs on the board flash when data is being transmitted via the FTDI chip and the USB connection to the computer (but not for serial communication on pins 0 and 1). A SoftwareSerial library allows for serial communication on any of the Nano's digital pins. The ATmega328 also supports I2C and SPI communication. The Arduino software includes the Wire library to simplify use of the I2C bus.

Automatic (software) reset 
Rather than requiring a physical press of the reset button before an upload, the Arduino Nano is designed in a way that allows it to be reset by software running on a connected computer. One of the hardware flow control lines (DTR) of the FT232RL is connected to the reset line of the ATmega328 via a 100 nanofarad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip.

This setup has other implications. When the Nano is connected to a computer running Mac OS X or Linux, it resets each time a connection is made to it from software (via USB). For the following half-second or so, the bootloader is running on the Nano. While it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of data sent to the board after a connection is opened.

Arduino board comparison
The following table compares official Arduino boards, and has a similar layout as a table in the Arduino Uno article.  The table is split with dark bars into three high-level microcontroller groups: 8-bit AVR cores, 32-bit ARM Cortex-M cores, and 32-bit ESP32 microcontrollers.  Though 3rd-party boards have similar board names it doesn't automatically mean they are 100% identical to official Arduino boards.  3rd-party boards often have a different voltage regulator / different USB-to-UART chip / different color solder mask, and some have a different USB connector or additional features, too.

Table notes
 Board Size Group column - Simplified board dimension size grouping: Nano means similar size as Arduino Nano board.  This table has a similar layout as a table in the Arduino Uno article.
 MCU Part# / Pins column - MCU means microcontroller. All MCU information in this table was sourced from official datasheets in this column. The pin count is useful to determine the quantity of internal MCU features that are available.  All MCU hardware features may not be available at the Nano header pins because the MCU IC package has more pins than the 30 header pins on the Nano board (*).
 MCU I/O Voltage column - Microcontrollers on official Arduino boards are powered at a fixed voltage of either 3.3 or 5 volts.  The voltage rating of the microcontroller is stated inside parenthesis, though Arduino boards don't support this full range.
 MCU Clock column - MHz means 106 Hertz.  The ATmega328P MCU is rated for a maximum of 20 MHz, but the Nano board operates at 16 MHz.
 MCU memory columns - KB means 1024 bytes, MB means 10242 bytes.
 MCU SRAM column - SRAM size doesn't include caches or peripheral buffers.
 MCU USART/UART column - USARTs are software configurable to be a: UART / SPI / other peripherals (varies across MCUs).
 MCU Other Bus Peripherals column - For USB bus, "FS" means Full Speed (12Mbps max), "HS" means High Speed (480Mbps max). For CAN bus, "A" means CAN 2.0A, "B" means CAN 2.0B, "FD" means CAN-FD. The RP2040 (Nano RP2040 Connect board) has a programmable I/O controller that can emulate various buses. Some buses require additional external circuitry to operate.
 MCU Timers column - The numbers in this column are the total number of each timer bit width, for example, the ATmega328P has one 16-bit timer and two 8-bit timers. "WD" means Watchdog timer, "RT" means Real Time Counter/Timer, "RC" means Real Time Clock (sec/min/hr). The 24-bit SysTick timer(s) inside the ARM cores aren't included in the 24-bit total in this column. PWM features are not documented in this table.

See also
 AVR microcontrollers
 Atmel AVR instruction set
 In-system programming

References

Further reading

External links

 
 Nano Schematic
Programming Cheat Sheets
 Sheet1, Sheet2

Arduino