Arduino Mega 2560

Overview

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560 (datasheet). It has 54 digital input/output

pins (of 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 for the Arduino Duemilanove or Diecimila.

Schematic & Reference Design

EAGLE files: arduino-mega2560-reference-design.zip

Schematic: arduino-mega2560-schematic.pdf

Summary

Microcontroller ATmega2560

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

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

Analog Input Pins 16

DC Current per I/O Pin 40 mA

DC Current for 3.3V Pin 50 mA

Flash Memory 256 KB of which 8 KB used by bootloader

SRAM 8 KB

EEPROM 4 KB

Clock Speed 16 MHz

Power

The Arduino Mega 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.

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 Mega2560 differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it

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

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. The regulated power supply used to power the microcontroller and other components on the board. This can come

either from 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.

Memory

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).

Input and Output

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 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 attachInterrupt() function for details.

PWM: 0 to 13. 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.

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 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.

There are a couple of other pins on the board:

AREF. Reference voltage for the analog inputs. Used with analogReference().

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 Mega2560 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 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 Mega2560's digital pins.

The ATmega2560 also supports I2C (TWI) and SPI communication. The Arduino software includes a Wire library to

simplify use of the I2C bus; see the documentation on the Wiring website for details. For SPI communication, use the SPI

library.

Programming

The Arduino Mega can be programmed with the Arduino software (download). For details, see the reference 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 of an external hardware programmer. It communicates using the original STK500 protocol (reference, C

header files).

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

header; see these instructions for details.

The ATmega8U2 firmware source code is available in the Arduino repository. The ATmega8U2 is loaded with a DFU

bootloader, which can be activated by connecting the solder jumper on the back of the board (near the map of Italy) and

then resetting the 8U2. 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

bootloader). See this user-contributed tutorial for more information.

Automatic (Software) Reset

Rather then requiring a physical press of the reset button before an upload, the Arduino Mega2560 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 Mega2560 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 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.

USB Overcurrent Protection

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.

Physical Characteristics and Shield Compatibility

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 I2C is not located on the same pins on the Mega (20 and 21) as the Duemilanove / Diecimila

(analog inputs 4 and 5).

ICSP

+5V

GND

+5V

GND

GND

+5V

GNDGND

47u 47u

GND GND

GN

D

GND

GREEN

GN

D

+5V

M7

GND

MC33269D-5.0

MC33269ST-5.0T3

100n

GND100n

100n

+3V3

+5V

+5V

ATMEGA1280-16AU

100n100n

22p

+5V

GND

100n

GND

100n

YELLOW

YELLOW

500mA

+5V

100n

GND

YELLOW

GN

D

100n

FDN340P

LM358DLM358D

GND

100n

GND

+5V

100n

+5V

GND

+5V

GND

1u

+5V

ATMEGA8U2-MU

ICSP

+5V

GND

GND

16MHz

GN

D

GND

BLM21

PG

B10

1060

4

PG

B10

1060

4

16MHz

GN

D

1M

1k

1k

1k

1k

10K

10K

10K

10K10

K

10K

10K

10K

1k

1k

1k

1k

22R

22R

22R

22R

GNDTS42

1M

16M

Hz

16M

Hz

22p

22p

22p

22p

GN

D

GN

D

GND

27R

27R

1 23 45 6

ICSP

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PWML

12345678

PWMH

PC1 PC2

OND1

11

22

3 3

VI3

1

VO 2

IC2

ADJ

1

IN3 OUT 42

IC1

123456

POWER

C3

C6

C2

12345678

ADCL

12345678

COMMUNICATION

(A8)PC0 53(A9)PC1 54

(A10)PC2 55(A11)PC3 56(A12)PC4 57(A13)PC5 58(A14)PC6 59(A15)PC7 60

(AD0)PA0 78(AD1)PA1 77(AD2)PA2 76(AD3)PA3 75(AD4)PA4 74(AD5)PA5 73(AD6)PA6 72(AD7)PA7 71

(ADC0)PF0 97(ADC1)PF1 96(ADC2)PF2 95(ADC3)PF3 94

(ADC4/TCK)PF4 93(ADC5/TMS)PF5 92(ADC6/TDO)PF6 91(ADC7/TDI)PF7 90

(ALE)PG2 70

(CLKO/ICP3/INT7)PE7 9

(ICP1)PD4 47

(MISO/PCINT3)PB3 22

(MOSI/PCINT2)PB2 21

(OC0A/OC1C/PCINT7)PB7 26

(OC0B)PG5 1

(OC1A/PCINT5)PB5 24(OC1B/PCINT6)PB6 25

(OC2A/PCINT4)PB4 23

(OC3A/AIN1)PE3 5(OC3B/INT4)PE4 6(OC3C/INT5)PE5 7

(RD)PG1 52

(RXD0/PCIN8)PE0 2

(RXD1/INT2)PD2 45

(SCK/PCINT1)PB1 20

(SCL/INT0)PD0 43(SDA/INT1)PD1 44

(SS/PCINT0)PB0 19

(T0)PD7 50

(T1)PD6 49

(T3/INT6)PE6 8

(TOSC1)PG4 29

(TOSC2)PG3 28

(TXD0)PE1 3

(TXD1/INT3)PD3 46

(WR)PG0 51

(XCK0/AIN0)PE2 4

(XCK1)PD5 48

AGND99

AREF98

AVCC100

GND11326281

PH0(RXD2)12PH1(TXD2)13PH2(XCK2)14PH3(OC4A)15PH4(OC4B)16PH5(OC4C)17PH6(OC2B)18PH7(T4)27

PJ0(RXD3/PCINT9)63PJ1(TXD3/PCINT10)64PJ2(XCK3/PCINT11)65PJ3(PCINT12)66PJ4(PCINT13)67PJ5(PCINT14)68PJ6(PCINT15)69PJ779

PK0(ADC8/PCINT16)89PK1(ADC9/PCINT17)88PK2(ADC10/PCINT18)87PK3(ADC11/PCINT19)86PK4(ADC12/PCINT20)85PK5(ADC13/PCINT21)84PK6(ADC14/PCINT22)83PK7(ADC15/PCINT23)82

PL0(ICP4)35PL1(ICP5)36PL2(T5)37PL3(OC5A)38PL4(OC5B)39PL5(OC5C)40PL641PL742

RESET30

VCC10316180

XTAL134

XTAL233

GNDGNDGND

VCCVCC

VCC

IC3

C5C4

12345678

ADCH

C1

C8

C13

RX

TX

1234P

$1P

$1P

$2P

$2

X2 F1

C9

L

C7

T2

2

31

IC5A

6

57

IC5B

84

C12C11

1 23 45 67 89 10

11 1213 1415 16

XIOH

1 23 45 67 89 10

11 1213 1415 16

XIOL

1 JP1

1 JP2

1 JP3

1 JP4

21

RESET-EN

C10

(PCINT9/OC1B)PC5 25

(PCINT10)PC4 26

(INT4/ICP1/CLK0)PC7 22

(OC1A/PCINT8)PC6 23

(AIN2/PCINT11)PC2 5

(PCINT5)PB5 19

(T1/PCINT4)PB4 18

(PD0/MISO/PCINT3)PB3 17

(PDI/MOSI/PCINT2)PB2 16

(SCLK/PCINT1)PB1 15

(SS/PCINT0)PB0 14

(CTS/HWB/AIN6/TO/INT7)PD7 13

(RTS/AIN5/INT6)PD6 12

(XCK/AIN4/PCINT12)PD5 11

(INT5/AIN3)PD4 10

(TXD1/INT3)PD3 9

(RXD1/AIN1/INT2)PD2 8

(AIN0/INT1)PD1 7

(OC0B/INT0)PD0 6

GND3VCC4

AVCC32

UVCC31

XTAL11

XTAL2(PC0)2

RESET(PC1/DW)24

UGND28

IC4

PADEXP

UCAP27

D-30

D+29

(PCINT6)PB6 20(PCINT7/OC0A/OC1C)PB7 21

1 23 45 6

ICSP1

Y2

21

UB

OO

T

L1

Z1 Z2

21

GROUND

Y1

R1

1 8

RN4A

2 7

RN4B

3 6

RN4C

4 5

RN4D

18

RN

5A

27

RN

5B3

6

RN

5C

4 5

RN5D

18

RN

1A

27

RN

1B

36

RN

1C

4 5

RN1D

1 8

RN3A2 7

RN3B

3 6RN3C

45RN3D

18 RN2A

2 7

RN2B3 6

RN2C

45 RN2D

134 2

RESET

5

R2

21Q1

21Q2

C14

C15

C16

C17

IN1

EN3

NC/FB 4

OUT 5

GND2

R3

R4

+5V

+5V

GNDAREF

AREF

AREF

RESET

RESET

RESET

RESET

RESET

VIN

VIN

VIN

M8RXD

M8RXD

M8TXD

M8TXD

PWRIN

ADC0

ADC2ADC1

ADC3ADC4ADC5ADC6ADC7

+3V3

+3V3+3V3

SDA

SDA

SCL

SCL

ADC9ADC8

ADC10ADC11ADC12ADC13ADC14ADC15

PB3

PB3

PB3

PB2

PB2

PB2

PB1

PB1

PB1

PB5PB4

PE5

PE5PE4

PE4PE3

PE3

PE1 PE1

PE1

PE0 PE0

PE0

DTR

USBVCC

USBVCC

USBVCC

GATE_CMD

CMP

PB6

PH3

PH3

PH4

PH4

PH5

PH5

PH6

PH6

PG5

PG5

RXD1TXD1RXD2

RXD2

RXD3

RXD3

TXD2

TXD2

TXD3

TXD3

PC0

PC0

PC1

PC1

PC2

PC2

PC3

PC3

PC4

PC4

PC5

PC5

PC6

PC6

PC7

PC7

PB0

PB0

PG0

PG0

PG1

PG1

PG2

PG2

PD7

PD7

PA0 PA0PA1

PA1

PA2PA2

PA3

PA3

PA4

PA4

PA5

PA5

PA6

PA6

PA7

PA7

PL0

PL0

PL1

PL1

PL2

PL2PL3

PL3 PL4PL4

PL5

PL5

PL6

PL6

PL7

PL7

PB7

VUCAP

RD-

RD-

RD+

RD+

RESET2

RESET2

MISO2

MISO2

MOSI2

MOSI2

SCK2

SCK2

XVCC

RXLTXL

D-D+

UG

ND

UGND

US

HIE

LD

XTAL2

XTAL2

XTAL1

XTAL1

XT2

XT2

XT1

XT1

XTAL1R

XT1R

+ +

US

B

01234567

8910111213

15161718192021

14

(SCK)(MISO)

(MOSI)

pwmpwmpwmpwm

pwmpwmpwm

pwmpwmpwmpwmpwm

pwmpwmpwm

(TX0)(RX0)

515253

pwmpwm

pwm

pwmpwm

(MISO)

(SCK)(MOSI)

(SS)(MOSI)

(SCK)(MISO)

222324252627282930323436

31333537

494745434139

50484644424038

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Arduino Mega 2560 Reference DesignTM

Reference Designs ARE PROVIDED "AS IS" AND "WITH ALL FAULTS". Arduino DISCLAIMS ALL OTHER WARRANTIES, EXPRESS OR IMPLIED,

Arduino may make changes to specifications and product descriptions at any time, without notice. The Customer must not

REGARDING PRODUCTS, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE

rely on the absence or characteristics of any features or instructions marked "reserved" or "undefined." Arduino reservesthese for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to them.The product information on the Web Site or Materials is subject to change without notice. Do not finalize a design with this information.