USB Over-current Protection The Arduino Mega 2560 R3 Board has a resettable polyfuse that protects your computer’s USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port. The fuse will automatically break the connection until the short or overload is removed. Input and Output Each of the 50 digital pins on the Mega R3 Android Accessory Development Kit (ADK) can be used as an input or output; using pin Mode(), digital Write(), and digital Read() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA . has an internal pull-up resistor (disconnect by default) of 20-50k Ohm. In addition, some pins have specialized functions: Serial : 0 (RX) and 1 (TX), Serial 1: 19 (RX) and 18 (TX), Serial 2: 17 (RX) and 16 (TX), Serial 3: 15 (RX) and 14 (TX). Use to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1 are also connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip. External Interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2). These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attach Interrupt() function for details. PWM: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analog Write() function. SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication using the SPI library. The SPI pins are also broken out on the ICSP header, which is physically compatible with the Uno, Duemilanove, and Diecimila. USB Host: MAX3421E.
