Arduino Mega ADK User manual

Arduino Mega ADK
User Manual
Getting Started
In the Getting Started section, you can find all the information you need to configure your
board, use the Arduino Software (IDE), and start to tinker with coding and electronics.
Power
The Arduino MEGA ADK can be powered via the USB connection or with an external power
supply. The power source is selected 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. Leads from a battery can be inserted in the Gnd and Vin pin headers of the
POWER connector.
NB: Because the MEGA ADK is a USB Host, the phone will attempt to draw power from it
when it needs to charge. When the ADK is powered over USB, 500mA total is available for
the phone and board. The external power regulator can supply up to 1500mA. 750mA is
available for the phone and MEGA ADK board. An additional 750mA is allocated for any
actuators and sensors attached to the board. A power supply must be capable of providing
1.5A to use this much current.
The board can operate on an external supply of 5.5 to 16 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
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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.
Memory
The MEGA ADK 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).
Input and Output
Each of the 50 digital pins on the MEGA ADK can be used as an input or output, using pin
Mode (),digitalWrite(), and digital Read() 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 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.
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The MAX3421E comunicate with Arduino with the SPI bus. So it uses the following pins:
 Digital: 7 (RST), 50 (MISO), 51 (MOSI), 52 (SCK).
NB: Please do not use Digital pin 7 as input or output because is used in the communication
with MAX3421E
 Non broken out on headers: PJ3 (GP_MAX), PJ6 (INT_MAX), PH7 (SS).
 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 MEGA ADK 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 analog Reference () function.
There are a couple of other pins on the board:
 AREF. Reference voltage for the analog inputs. Used with analog Reference ().
 Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button
to shields which block the one on the board.
Communication
The Arduino MEGA ADK has a number of facilities for communicating with a computer,
another Arduino, or other microcontrollers. The ATmega2560 provides four
hardware UARTs for TTL (5V) serial communication. An ATmega8U2 on the board channels
one of these over USB and provides a virtual com port to software on the computer
(Windows machines will need a .inf file, but OSX and Linux machines will recognize the board
as a COM port automatically. The Arduino software includes a serial monitor which allows
simple textual data to be sent to and from the board. The RX and TX LEDs on the board will
flash when data is being transmitted via the ATmega8U2/16U2 chip and USB connection to
the computer (but not for serial communication on pins 0 and 1).
A SoftwareSerial library allows for serial communication on any of the MEGA ADK's digital
pins.
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The ATmega2560 also supports TWI and SPI communication. The Arduino software includes
a Wire library to simplify use of the TWI bus; see the Wire library for details. For SPI
communication, use the SPI library.
The USB host interface given by MAX3421E IC allows the Arduino MEGA ADK to connect
and interact to any type of device that have a USB port. For example, allows you to interact
with many types of phones, controlling Canon cameras, interfacing with keyboard, mouse and
games controllers as Wiimote and PS3.

Programming
The ATmega2560 on the Arduino MEGA ADK comes pre-burned with a bootloader (the same
on Mega 2560) that allows you to upload new code to it without the use of an external
hardware programmer. It communicates using the original STK500v2 protocol (reference, C
header files).
You can also bypass the boot loader and program the microcontroller through the ICSP (In-
Circuit Serial Programming) header using Arduino ISP or similar; see these instructions for details.
The ATmega8U2 firmware source code is available in the Arduino repository.
The ATmega8U2 is loaded with a DFU boot loader, which can be activated by:
 On Rev1 boards: connecting the solder jumper on the back of the board (near the map of
Italy) and then resetting the 8U2.
 On Rev2 or later boards: there is a resistor that pulling the 8U2/16U2 HWB line to ground,
making it easier to put into DFU mode. You can then use Atmel's FLIP software (Windows) or
the DFU programmer (Mac OS X and Linux) to load a new firmware. Or you can use the ISP
header with an external programmer (overwriting the DFU boot loader).
Automatic (Software) Reset
Rather then requiring a physical press of the reset button before an upload, the Arduino
MEGA ADK is designed in a way that allows it to be reset by software running on a connected
computer. One of the hardware flow control lines (DTR) of the ATmega8U2 is connected to
the reset line of the ATmega2560 via a 100 nanofarad capacitor. When this line is asserted
(taken low), the reset line drops long enough to reset the chip. The Arduino software uses
this capability to allow you to upload code by simply pressing the upload button in the Arduino
environment. This means that the bootloader can have a shorter timeout, as the lowering of
DTR can be well-coordinated with the start of the upload.
This setup has other implications. When the MEGA ADK is connected to either a computer
running Mac OS X or Linux, it resets each time a connection is made to it from software (via
USB). For the following half-second or so, the bootloader is running on the MEGA ADK.
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 MEGA ADK 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.
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USB Overcurrent Protection
The Arduino MEGA ADK has a resettable poly fuse 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.
Physical Characteristics and Shield Compatibility
The maximum length and width of the MEGA ADK 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 MEGA ADK 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
MEGA ADK and Duemilanove / Diecimila.Please note that I2C is not located on the same pins
on the MEGA ADK (20 and 21) as the Duemilanove / Diecimila (analog inputs 4 and 5).
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