Datasheet

USB). For the following half-second or so, the bootloader is running on the Mega2560. While

it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it

will intercept the first few bytes of data sent to the board after a connection is opened. If a

sketch running on the board receives one-time configuration or other data when it first starts,

make sure that the software with which it communicates waits a second after opening the

connection and before sending this data.

The Mega2560 contains a trace that can be cut to disable the auto-reset. The pads on either

side of the trace can be soldered together to re-enable it. It's labeled "RESET-EN". You may

also be able to disable the auto-reset by connecting a 110 ohm resistor from 5V to the reset

line; see this forum thread for details.

The Arduino Mega2560 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.

The maximum length and width of the Mega2560 PCB are 4 and 2.1 inches respectively, with

the USB connector and power jack extending beyond the former dimension. Three screw

holes allow the board to be attached to a surface or case. Note that the distance between

digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other

pins.

The Mega2560 is designed to be compatible with most shields designed for the Uno,

Diecimila or Duemilanove. Digital pins 0 to 13 (and the adjacent AREF and GND pins),

analog inputs 0 to 5, the power header, and ICSP header are all in equivalent locations.

Further the main UART (serial port) is located on the same pins (0 and 1), as are external

interrupts 0 and 1 (pins 2 and 3 respectively). SPI is available through the ICSP header on

both the Mega2560 and Duemilanove / Diecimila. Please note that I

C is not located on the

same pins on the Mega (20 and 21) as the Duemilanove / Diecimila (analog inputs 4 and 5).