The board is a micro-controller board base on the ATmega2560. It has a USB host interface to connect with Android based phones, base on the MAX3421e IC.
It has 54 digital input/output pins (of which 15 can be used as PWM outputs); 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator; a USB connection, a power jack, an ICSP header, and a reset button. It features an ATmega8U2 program as a USB-to-serial converter. Revision 3 of the Mega ADK board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU(Device Firmware Upgrade) mode.
The board has the following new features: 1.0 pin-out: added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In the future, shields will be compatible both with the board that uses the AVR, which operate with 5V and with the Arduino Due that operates with 3.3V. The second one is a not connected pin, that is reserved for future purposes. Stronger RESET circuit.
The power source is select automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board’s power jack.