Description
The Mega R3 Android Accessory Development Kit (ADK) is a powerful microcontroller board built around the ATmega2560. Its distinguishing feature is an integrated USB host interface, facilitated by the MAX3421e IC, enabling direct communication with Android-based phones. This board offers a comprehensive set of I/O, including 54 digital input/output pins (15 capable of PWM output), 16 analog inputs, and four hardware UARTs for serial communication. The Revision 3 board incorporates a 1.0 pin-out with dedicated SDA, SCL, and IOREF pins, enhancing compatibility with future shields and a more robust reset circuit.
Powering the Mega R3 ADK is flexible, supporting either the USB connection or an external power supply, with automatic source selection. External power can be delivered via an AC-to-DC adapter (7-12V recommended, 6-20V limits) or battery. The board’s design, particularly its USB Host capability, allows it to provide power to connected Android phones, offering up to 500mA total when USB-powered. For applications requiring more power, the external regulator can supply up to 1500mA, with 750mA allocated for the phone and board, and an additional 750mA for connected actuators and sensors, provided the power supply can meet this demand.
Memory resources include 256 KB of flash memory for code storage (with 8 KB reserved for the bootloader), 8 KB of SRAM, and 4 KB of EEPROM. Beyond standard digital and analog I/O, the board supports various communication protocols like SPI (pins 50-53), TWI/I2C (pins 20 and 21), and multiple UARTs. It features a built-in LED on pin 13 and an AREF pin for analog reference voltage adjustments. A resettable polyfuse offers protection against overcurrent conditions on the USB port, safeguarding connected computers. The board’s physical characteristics ensure compatibility with most Arduino Uno/Duemilanove shields, although I2C pin locations differ.
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