Datasheet

power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the
POWER connector.
The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V,
however, the 5V pin may supply less than five volts and the board may be unstable. If using
more than 12V, the voltage regulator may overheat and damage the board. The recommended
range is 7 to 12 volts.
The power pins are as follows:
VIN. The input voltage to the Arduino board when it's using an external power source (as
opposed to 5 volts from the USB connection or other regulated power source). You can supply
voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.
5V. This pin outputs a regulated 5V from the regulator on the board. The board can be
supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the
VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the
regulator, and can damage your board. We don't advise it.
3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50
mA.
GND. Ground pins.
IOREF. This pin on the Arduino board provides the voltage reference with which the
microcontroller operates. A properly configured shield can read the IOREF pin voltage and
select the appropriate power source or enable voltage translators on the outputs for working
with the 5V or 3.3V.
The ATmega2560 has 256 KB of flash memory for storing code (of which 8 KB is used for the
bootloader), 8 KB of SRAM and 4 KB of EEPROM (which can be read and written with the
EEPROM library).
Each of the 54 digital pins on the Mega can be used as an input or output, using pinMode(),
digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or
receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default)
of 20-50 kOhms. 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). Used to receive (RX) and transmit (TX) TTL serial
data. Pins 0 and 1 are also connected to the corresponding pins of the ATmega16U2 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
attachInterrupt() function for details.
PWM: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analogWrite() 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.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value,
the LED is on, when the pin is LOW, it's off.
TWI: 20 (SDA) and 21 (SCL). Support TWI communication using the Wire library. Note
that these pins are not in the same location as the TWI pins on the Duemilanove or Diecimila.
The Mega2560 has 16 analog inputs, each of which provide 10 bits of resolution (i.e. 1024
different values). By default they measure from ground to 5 volts, though is it possible to
change the upper end of their range using the AREF pin and analogReference() function.