Starting with hardware, the Arduino Mega is based on the Atmega2560 microcontroller. In the iteration that is found on the Mega board, the microcontroller comes in a standard TQFP 100-pin package.

Kicad schematic for Atmega 2560. This includes the most basic elements to create a project with Atmega 2560 (Arduino Mega). This design only includes the most basic elements to work with the ...

It’s a significant update. The Arduino UNO and Arduino Mega 2560 update the Duemilanove and Mega respectively. They now use an ATMega8U2 instead of an FTDI USB to serial converter chip.

Meanwhile, the Arduino Mega is getting the same USB chip along with an ATMega2560 processor with twice the memory. Right now only 128K is available, but that's a software limitation and they're ...