Official Arduino Mega 2560 Rev3 Development Board (ATmega2560)

The Arduino board for projects that outgrow the Uno

The Arduino Mega 2560 Rev3 is a microcontroller board built around the ATmega2560 chip, aimed at projects that need more I/O than an Uno can offer. It carries 54 digital input/output pins, of which 15 can be used as PWM outputs, alongside 16 analog inputs, four hardware serial ports (UARTs), a 16MHz crystal oscillator, a USB connection, a power jack, an ICSP header and a reset button.

That pin count matters most on builds with many actuators and sensors at once, such as multi-motor robots, large LED installations or projects juggling several serial-connected modules (GPS, Bluetooth, a display) where four separate UARTs avoid the need to multiplex a single serial port.

What Rev3 changed

This revision uses an ATmega16U2 chip to handle the USB-to-serial conversion, a dedicated chip separate from the main ATmega2560, which also brings a stronger reset circuit than earlier Mega revisions. The board runs on 5V, with a recommended input voltage of 7 to 12V and an absolute limit of 6 to 20V, and each I/O pin can supply up to 40mA.

Onboard memory totals 256KB of flash, of which 8KB is used by the bootloader, alongside 8KB of SRAM and 4KB of EEPROM. Because the header layout matches the Uno's, most shields designed for the Uno will physically fit and electrically work on the Mega, though shields relying on specific Uno-only pins may need adjustment.

Who should choose it

Anyone building a project that has already outgrown an Uno's 20 or so I/O pins, or that needs multiple simultaneous serial connections, will find the Mega 2560 the natural next step while staying within the familiar Arduino IDE and ecosystem.

Questions buyers ask

How many I/O pins does it have?

54 digital I/O pins, 15 of which support PWM, plus 16 analog inputs.

How many serial ports does it have?

Four hardware UARTs.

Are Uno shields compatible?

Most shields designed for the Uno fit the Mega's pin layout and will work, though some Uno-specific designs may need adjustment.