Arduino Mega 2560 User manual

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560

(datasheet). It has 54 digital input/output pins (o which 14 can be used as PWM outputs),

16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB

connection, a power jack, an ICSP header, and a reset button. It contains everything

needed to support the microcontroller; simply connect it to a computer with a USB cable or

power it with a AC-to-DC adapter or battery to get started. The Mega is compatible with

most shields designed or the Arduino Duemilanove or Diecimila.

EAGLE iles: arduino-mega2560-re erence-design.zip Schematic: arduino-mega2560-schematic.pd

Microcontroller ATmega2560

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins 54 (o which 14 provide PWM output)

Analog Input Pins 16

DC Current per I/O Pin 40 mA

DC Current or 3.3V Pin 50 mA

Flash Memory 256 KB o which 8 KB used by bootloader

SRAM 8 KB

EEPROM 4 KB

Clock Speed 16 MHz

The Arduino Mega2560 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 rom 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 rom a battery

can be inserted in the Gnd and Vin pin headers o the POWER connector.

The board can operate on an external supply o 6 to 20 volts. I supplied with less than 7V, however, the 5V pin may

supply less than ive volts and the board may be unstable. I using more than 12V, the voltage regulator may overheat

and damage the board. The recommended range is 7 to 12 volts.

The Mega2560 di ers rom all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it

eatures the Atmega8U2 programmed as a USB-to-serial converter.

The power pins are as ollows:

•VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts

rom the USB connection or other regulated power source). You can supply voltage through this pin, or, i

supplying voltage via the power jack, access it through this pin.

•5V. The regulated power supply used to power the microcontroller and other components on the board. This

can come either rom VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

•3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

•GND. Ground pins.

The ATmega2560 has 256 KB o lash memory or storing code (o which 8 KB is used or the bootloader), 8 KB o

SRAM and 4 KB o EEPROM (which can be read and written with the EEPROM library).

Each o the 54 digital pins on the Mega can be used as an input or output, using pinMode(), digitalWrite(), and

digitalRead() unctions. They operate at 5 volts. Each pin can provide or receive a maximum o 40 mA and has an

internal pull-up resistor (disconnected by de ault) o 20-50 kOhms. In addition, some pins have specialized unctions:

•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

1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1 are also connected to the

corresponding pins o the ATmega8U2 USB-to-TTL Serial chip .

•External Interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt ), 20 (interrupt 3), and 21

(interrupt 2). These pins can be con igured to trigger an interrupt on a low value, a rising or alling edge, or a

change in value. See the attachInterrupt() unction or details.

•PWM: 0 to 13. Provide 8-bit PWM output with the analogWrite() unction.

•SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication, which, although

provided by the underlying hardware, is not currently included in the Arduino language. The SPI pins are also

broken out on the ICSP header, which is physically compatible with the 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 o .

•I2C: 20 (SDA) and 21 (SCL). Support I2C (TWI) communication using the Wire library (documentation on the

Wiring website). Note that these pins are not in the same location as the I2C pins on the Duemilanove.

The Mega2560 has 16 analog inputs, each o which provide 10 bits o resolution (i.e. 1024 di erent values). By de ault

they measure rom ground to 5 volts, though is it possible to change the upper end o their range using the AREF pin and

analogRe erence() unction.

There are a couple o other pins on the board:

•AREF. Re erence voltage or the analog inputs. Used with analogRe erence().

•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.

The Arduino Mega2560 has a number o acilities or communicating with a computer, another Arduino, or

other microcontrollers. The ATmega2560 provides our hardware UARTs or TTL (5V) serial communication.

An ATmega8U2 on the board channels one o these over USB and provides a virtual com port to so tware on

the computer (Windows machines will need a .in ile, but OSX and Linux machines will recognize the board

as a COM port automatically. The Arduino so tware includes a serial monitor which allows simple textual

data to be sent to and rom the board. The RX and TX LEDs on the board will lash when data is being

transmitted via the ATmega8U2 chip and USB connection to the computer (but not or serial communication

on pins 0 and 1).

A So twareSerial library allows or serial communication on any o the Mega's digital pins.

The ATmega2560 also supports I2C (TWI) and SPI communication. The Arduino so tware includes a Wire

library to simpli y use o the I2C bus; see the documentation on the Wiring website or details. To use the SPI

communication, please see the ATmega2560 datasheet.

The Arduino Mega2560 can be programmed with the Arduino so tware (download). For details, see the

re erence and tutorials.

The Atmega2560 on the Arduino Mega comes preburned with a bootloader that allows you to upload new

code to it without the use o an external hardware programmer. It communicates using the original STK500

protocol (re erence, C header iles).

You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial

Programming) header; see these instructions or details.

Rather then requiring a physical press o the reset button be ore an upload, the Arduino Mega2560 is

designed in a way that allows it to be reset by so tware running on a connected computer. One o the

hardware low control lines (DTR) o the ATmega8U2 is connected to the reset line o the ATmega2560 via a

100 nano arad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the

chip. The Arduino so tware 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 o DTR can be well-coordinated with the start o the upload.

This setup has other implications. When the Mega2560 is connected to either a computer running Mac OS X

or Linux, it resets each time a connection is made to it rom so tware (via USB). For the ollowing hal -second

or so, the bootloader is running on the Mega2560. While it is programmed to ignore mal ormed data (i.e.

anything besides an upload o new code), it will intercept the irst ew bytes o data sent to the board a ter a

connection is opened. I a sketch running on the board receives one-time con iguration or other data when it

irst starts, make sure that the so tware with which it communicates waits a second a ter opening the

connection and be ore sending this data.

The Mega contains a trace that can be cut to disable the auto-reset. The pads on either side o 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 rom 5V to the reset line; see this orum thread or details.

The Arduino Mega has a resettable poly use that protects your computer's USB ports rom shorts and

overcurrent. Although most computers provide their own internal protection, the use provides an extra layer

o protection. I more than 500 mA is applied to the USB port, the use will automatically break the connection

until the short or overload is removed.

The maximum length and width o the Mega PCB are 4 and 2.1 inches respectively, with the USB connector

and power jack extending beyond the ormer dimension. Three screw holes allow the board to be attached to

a sur ace or case. Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple

o the 100 mil spacing o the other pins.

The Mega is designed to be compatible with most shields designed or the 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 and Duemilanove / Diecimila. Please note that I2C is not located on the same pins on the

Mega (20 and 21) as the Duemilanove / Diecimila (analog inputs and 5).

Arduino can sense the environment by receiving input rom a variety o sensors and can a ect its

surroundings by controlling lights, motors, and other actuators. The microcontroller on the board is

programmed using the Arduino programming language (based on Wiring) and the Arduino

development environment (based on Processing). Arduino projects can be stand-alone or they can

communicate with so tware on running on a computer (e.g. Flash, Processing, MaxMSP).

Arduino is a cross-plato orm program. You’ll have to ollow di erent instructions or your personal

OS. Check on the Arduino site or the latest instructions. http://arduino.cc/en/Guide/HomePage

Once you have downloaded/unzipped the arduino IDE, you can Plug the Arduino to your PC via USB cable.

Now you’re actually ready to “burn” your

irst program on the arduino board. To

select “blink led”, the physical translation

o the well known programming “hello

world”, select

File>Sketchbook>

Arduino-0017>Examples>

Digital>Blink

Once you have your skecth you’ll

see something very close to the

screenshot on the right.

In Tools>Board select MEGA

Now you have to go to

Tools>SerialPort

and select the right serial port, the

one arduino is attached to.

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