Arduino Mega 2560

First of all, Why Arduino Mega 2560?

When cheaper boards are available, why go with Arduino Mega? The main reason behind this is the additional features that are inbuilt with this board. First feature is the large I/O system design with inbuilt 16 analog transducers and 54 digital transducers that supports with USART and other communication modes. Secondly, it has inbuilt RTC and other features like analog comparator, advanced timer, interrupt for controller wakeup mechanism to save more power and fast speed with 16 Mhz crystal clock to get 16 MIBS. It has more than 5 pins for Vcc and Gnd to connect other devices to Arduino Mega.

Other features include JTAG support for programming, debugging and troubleshooting. With large FLASH memory and SRAM, this board can handle large system program with ease. It is also compatible with the different type of boards like high-level signal (5V) or low-level signal (3.3V) with I/O ref pin.

Brownout and watchdog help to make the system more reliable and robust. It supports ICSP as well as USB microcontroller programming with PC.

The Arduino Mega 2560 is a replacement of the old Arduino Mega, and so in general reference, it will be called without the ‘2560’ extension. Due to the many numbers of pins, it is not usually used for common projects but you can find them in much more complex ones like Radon detectors, 3D printers, temperature sensing, IOT applications, real-time data monitoring applications etc.

Arduino Mega 2560 Specifications

Arduino Mega – Basic Features

Arduino MegaFeatures
MicrocontrollerAVR ATmega 2560 (8bit)
Power Supply7-12V (Inbuilt Regulator for Controller)
Digital I/O Pins54
Analog I/O Pins16
Total Digital I/O70 (Digital + Analog)
Clock Speed16 MHz (Factory set to 1Mhz)
Flash Memory 128 KB
CommunicationUSB (Programming with ATmega 8), ICSP (programming), SPI, I2C and USART

Arduino Mega – Advanced Features

Arduino MegaAdvanced Features
Timer2 (8bit) + 4 (16bit) = 6 timer
PWM12 (2-16 bit)
ADC 16  (10 bit)
Pin Change Interrupt24

Arduino Mega 2560 is also packed with additional features like Analog Comparator, External Interrupt & Software Interrupt, Power Saving Mode, Inbuilt Temperature Sensor, RTC and more.

Arduino Mega Pinout

Arduino Mega Pinout
Arduino Mega Pinout

Power pins :

Arduino MegaPower Pins
VINSupply voltage (7-12V)
5V SupplyFor External hardware device power supply
3.3V SupplyFor External low voltage hardware device power supply

Arduino Mega Pin Diagram

Arduino Mega Pin Configuration
Arduino Mega Pin Configuration

Controller Pins:

RESET: (Reset input) A low level on this pin for longer than the 4 clock cycle will generate a reset. Arduino Mega has inbuilt reset circuit with push button to reset system and this pin can be used by other devices to reset controller.

XTAL1,XTAL2: Crystal (16Mhz) is connected to supply clock for controller with 2 bypass capacitor to ground.

AREF: This pin is used, when we use Adc for analog to digital conversion with external reference voltage for conversion and don’t want to use internal 1.1V or 5v reference.

Digital pins (70):
Digital pins (0-53) + Analog (0-15) = Total Digital I/O pins.

Digital Pins: From 0-53(digital) and 0-15(analog) can be use as input or output for digital transducer and output devices by pinMode() for pin direction, digtalWrite() to write pin and digitalRead() to read pin status.


Output devices : Relay, LED, buzzer, LCD and others.

Input devices: digital thermistor, push button, ultrasonic sensor, joystick and others


  • Output low signal on Arduino mega board



  • Input read signal on Arduino mega board



 Analog Pins (16):

Analog pins: From 0-15(analog) can be used as analog input pin for adc, if not used than it work as normal digital pin. It can be used by pinMode() for pin direction, analogRead() to read pin status and get digital value for analog signal, care must be taken for internal or external reference voltage selection and Aref pin.

Application :

Input devices: Ntc thermistor, sensors (like ldr, irled and humidity) and others

Example :

  • INPUT analog signal on Arduino mega board



Alternative Pins Function:

SPI Pins:
Pin 22 - SS, Pin 23 - SCK, Pin 24 - MOSI, Pin 25 – MISO

These pins are used for serial communication with SPI protocol for communication between 2 or more devices. SPI enable bit must be set to start communication with other devices.


Programming AVR controller, communication with others peripheral like LCD and SD card with four-line communication at high speed.

I2C Pins:

Digital pin 20 for SDA and 21 for SCK (Speed 400khz) to enable two wire communication with others devices. Function used are wire.begin() to start I2C conversion, with wire.Read() to read i2c data and wire.Write() to write i2c data.


Output devices : LCD and communication between multiple devices with two wire.

Input devices : rtc and others.


I2c master read data from slave


Wire.requestFrom(2, 1); //1byte data


PWM Pins:

Digital pin 2-13 can be used as PWM output with analogWrite() to write pwm value from 0-255.It’s alternative of DAC for low cost system to get analog signal at output by using filter.


Output devices: speed control of motor, light dimmer, pid for efficient control system.


  • OUTPUT analog signal on Arduino mega board



USART Pins :
Pin 0 – RXD0, pin 1 – TXD0

Pin 19 – RXD1, pin 18 – TXD1

Pin 17 – RXD2, pin 16 – TXD2

Pin 15 – RXD3, pin 14 – TXD3

This pin is used for serial usart communication with pc or other system for data sharing and logging. It is used with serialBegin() to set baud rate setting and start communication with serial.Println() to print array of char on other device output.


Two controller communication, pc and controller communication, debugging with usart by serial monitor.




Pinchange Interrupt Pins:
Digital Pin 0,22,23,24,25,10,11,12,13,15,14

Analog Pin 6,7,8,9,10,11,12,13,14,15

This pin is used for pin change interrupt. Enable bit of pinchange interrupt must be set with global interrupt enable.

Application :

Rotary encoder, push button based interrupt and others.

Example :

pinMode(0, OUTPUT);

pinMode(1, INPUT_PULLUP);

attachInterrupt(digitalPinToInterrupt(1), LOW, CHANGE);

Hardware Interrupt Pins :

Digital pin 18 – 21,2,3 hardware interrupt is used for interrupt services. Hardware interrupt must be enabled with global interrupt enable to get interrupt from other devices.


Push button for ISR program, wake up controller with external devices, sensors like ultrasonic and others.


pinMode(0, OUTPUT);

pinMode(1, INPUT_PULLUP);

attachInterrupt(digitalPinToInterrupt(1), LOW, LOW);

Arduino Mega Schematic Components:

 DC Jack Power Supply :

External Supply for Arduino Mega from range 7-12 volt is given with this port. Arduino Mega R3 has a voltage regulator for 5v and 3.3v supply for Arduino controller and sensor supply.

AVR 2560 :

This is the main controller used to program and run task for the system. This is the brain of the system to control all other devices on board.

ATmega8 :

This controller is used for communication between the main controller and other devices. This controller is programmed for USB communication and serial programming features.

ICSP 1 (ATmega8) and 2 (AVR 2560):

It has features of programming using serial bus with AVR programmer using SPI communication. AVR 2560 is programmed to run the system and ATmega 8 is programmed for serial communication and programming.

Arduino Mega ICSP Pinout
Arduino Mega ICSP Pinout for ATmega 2560

Reset :

It has reset circuit with capacitor, button and resistor to reset the controller. A push button is used to get 4 cycle low signal on reset pin to get the controller in reset mode.

Crystal :

It has a crystal circuit with two capacitors and one 16 Mhz crystal for xtal pins 1 and 2 interfacing with avr 2560.

I2C :

It has features of I2C (two wire communication) with an external pull-up resistor.


It has TXD and RXD pin for serial communication with LED indicator.

Some Simple Programs to try on Arduino Mega 2560

Program 1: Blinking LED (Digital pin)


Turns on an LED on for two second, then off for two second on pin 13, repeatedly.


// the setup function runs once when you press reset or power the board

void setup() {

// initialize digital pin 13 as an output.

pinMode(13, OUTPUT);


// the loop function runs again and again

void loop() {

digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)

delay(2000);                       // wait for two second

digitalWrite(13, LOW);    // turn the LED off

delay(2000);                       // wait for two second


Program 2:  Led Light Dimmer (PWM):

int brightness = 0;    //pwm value

void setup()


pinMode(3, OUTPUT);


void loop()


analogWrite(3, brightness);  // pwm write on pin 3

++brightness;  // brightness is incremented by 1

if (brightness <= 0 || brightness >= 255) {

brightness=0;  // brightness limited to 0-255




Program 3: Analog Read Voltage (Analog pin with USART) :

void setup()


Serial.begin(9600);  // usart communication start function with baudrate set to 9600


void loop()


int sensorValue = analogRead(A0);  // analog pin 0 data is read and converted into digital value stored in sensorValue.

Serial.println(sensorValue); // usart to output sensor value on serial monitor


You may also try your own logic and implement programs for Arduino mega with basic C and Arduino function.


1 Comment

  1. Julz Moore

    Are you sure the SPI pins on this page are correct?
    “Pin 22 – SS, Pin 23 – SCK, Pin 24 – MOSI, Pin 25 – MISO”

    The ATmega2560 datasheet for SPI shows:
    Pin 19 – SS, Pin 20 – SCK, Pin 21 – MOSI, Pin 22 – MISO.

    (arduino pin mapping: SS=53, SCK=52, MOSI=51, MISO=50)