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100 • August 2011 • electronics for you w w w . e f y m A g . c o m

Siddharth Mankad

Open Source Physical Computing

for BeginnersPyscl compug s o s mg s sous. Ee e auoplfom— plfom fo pyscl compug fo e beges

W s e auoplfom?

Arduino (pronounced as aar-do-we-

know) platform is a small and efcient

AVR development board for hobbyists.

It has been developed by Massimo

Banzi and the Arduino team. AVR

is the series of 8-bit RISC microcon-

trollers based on a modied Harvard

microcontroller architecture. The chips

used on the Arduino board include

the ATmega AVR family—ATmega8,

ATmega168, ATmega328 and the AT-

mega1280.

Since the Arduino platform is

Open Source, there have been manyclones, and many of these clones use

other processors too apart from the

ones listed above. The Arduino board

comes in many sizes for a varied num-

ber of applications, the most common

being the Arduino Duemilanove. The

Diecimila is the older version of the

Duemilanove. Other form factors in-

clude Arduino LilyPad (for wearable

computing; it can be sewn onto/into

clothes), Arduino Nano (for use with

breadboards), Arduino Mega (a more

powerful variant of the Duemilanove),

Arduino Pro (a cheaper version of the

Duemilanove meant for advanced us-

ers), Arduino Pro mini, Arduino Fio

and Arduino BT (for wireless applica-

tions; BT uses Bluetooth) and ArduinoSerial (unlike the other boards, it uses

a serial/RS-232 interface instead

of the USB for hook-up to the

computer).

The Duemilanove board is

suitable for starters. It is easy to

use since it’s USB-based.

te fumels

The rst thing is to get hold of

the hardware. In India, you can

get the board from feemo or

rhydoLABZ. The cheapest way

to assemble an Arduino is to use

the breadboard. Here, a blank

Arduino PCB with serial COM

port is used and the components

are soldered onto it. The parts

list is available on the ofcial

Arduino site with the schematic.

It is fairly easy to assemble.

The Arduino board with se-

rial COM port requires power(unlike the Duemilanove where

J

ust like chef Gusteau said in the

movie Ratatouille , “Anyone can

cook!” we could say, “Anyone can

prototype!” Let’s begin by simpli-

fying the term physical computing. It

denitely sounds too techie to a new-

bie. According to Wikipedia, physi-

cal computing, in the broadest sense

means building interactive physical

systems by the use of software and

hardware that can sense and respond

to the analogue world.

In other words, we can make de-

vices that use sensors as input and per-

form some action (physical or virtual)as output.

Fig. 1: The Arduino board



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external power is an option). You can

connect an AC-DC adaptor (~12V,

with centre pin positive). The board

can take up to 25V DC. Also, you will

require an FTDI cable (serial-to-USB)

if you do not have a COM port in your

computer.

Duemilanove users can just plug-

and-play after installing the drivers.

The FTDI USB drivers are with the

Arduino IDE in the ‘drivers’ folder.

Le’s ge ou s we

Here, the program ‘Blink’ is used to

explain, using the Duemilanove. Even

if the serial COM port version is usedthere will hardly be any difference per

se. The Arduino hardware is shown

in Fig. 2.

The digital input/output (I/O) pins

are where you can connect output de-

vices like motors, LCDs, touchscreens

and sensors for input. The analogue

input pins are where input sensors and

analogue input devices like potenti-

ometers (pots) can be connected. The

processor—ATmega—is the brain of

the entire operation.

Download the Arduino IDE from

the website and install it in your

system if you haven’t already done

so. Extract it. The Arduino can be

programmed from Windows, Macand Linux. Start the IDE and go to

File→Examples→Digital→Blink. The

code for blinking LED is listed below:

int ledPin = 13; // LED connected

to digital pin 13

// The setup() method runs once, when

the sketch starts

void setup() {

// initialize the digital pin as

an output:

pinMode(ledPin, OUTPUT);

}

// the loop() method runs over and

over again,

// as long as the Arduino has power

void loop()

{

digitalWrite(ledPin, HIGH); //

set the LED on

delay(1000); //

wait for a second

digitalWrite(ledPin, LOW); //

set the LED off

delay(1000); //

wait for a second

}

Arduino source code contains thefollowing sections:

1. The setup(), which runs only

once (automatically) when the pro-

gram starts running.

2. The loop(), which is an innite

loop that is triggered once setup()

completes.

3. Other user-dened functions.

In any program, the setup() and

loop() are mandatory. Any extra li-

braries used will have to be imported

using the ‘import’ statement before the

setup().

Coming back to the LED blinking

example, the rst line sets an integer

variable with the value of the pin at

which we have connected the LED. The

‘pinMode’ function tells the ATmega

whether the pin 13 (‘ledPin’ variable’s

value) has an input or an output device

connected to it. The rst argument is

the pin number. The LED is an output

component, hence pinMode’s secondargument would be output.

Fig. 2: The Arduino hardware

Fig. 3: Connecting the LED



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Related stuff and resources

Arduino has a large community and good support and documentation available on theinternet. The resources, references and links are below: www.arduino.cc (The Arduino Homepage) www.feemo.in (Feemo) www.rhydolabz.com (rhydoLABZ) http://www.arduino.cc/en/Main/StandaloneAssembly (Breadboard Arduino) http://lab.guilhermemartins.net/2009/05/06/paperduino-prints/ (Paperduino—make

Arduino on a cardboard)

Fig. 4: The Arduino IDE

Now we come to the loop(). The

rst line in loop(), ‘digitalWrite’ sends

voltage and current to the ledPin (pin

13) using the ‘high’ argument (‘high’

means ‘on’). This turns the LED on.

Then it gives a delay of 1000 millisec-

onds. This means that the LED remainson for 1000 milliseconds or 1 second.

After that the ‘low’ argument (line 3)

turns off the current and voltage on

the ledPin, and again (line 4) waits

for a second. These four lines will run

innitely.

Connect an LED to the board as

shown in Fig. 3. Connect the positive of

the LED (the longer leg) to digital pin

13 of ATmega chip and the other leg to

the GND digital pin.

Once the code is written, hit the

‘Play’ button (or CTRL+R) to compile

it. After compilation, the generated hex

le has to be uploaded to the ATmega.

Press File→Upload To I/O Board (or

CTRL+U). The programmer section

handles the burning of code into the

ATmega chip. The bootloader on the

ATmega kickstarts your loaded pro-

gram. The result is a blinking LED.

tg fow

The example is a simple demonstration

of physical computing, though we did

not use any input. You can now ex-

periment with various sensors like the

light dependent resistor (LDR) and say,

make a program that dims the LED if

the LDR is subjected to less light, and

vice versa.

Lots of interesting combinations of

sensors and outputs, actions and reac-

tions and a whole gamut of interactive

devices can be built. The references,

documentation and forums are avail-

able to help you out if you run into

any issues—Open Source Community!

People have used this in robotics, aero-

modeling, hobby projects and new

media applications. The Arduino can

control servo motors, stepper motors,

LCD screens, etc. It can take inputs

from pressure sensors, accelerometers,

GPS modules, gyroscopes, tempera-

ture sensors, humidity sensors, etc. It

can interface with XBee (wireless) and

bluetooth modules too. Even a basic

touchscreen (from the Nintendo DS)

can be used for interaction. The screen

is available readily and is cheap at

close to Rs 700.

The possibilities are immense.

What’s more is, that you could mash-

up and combine sensors to come up

with interesting new possibilities. All

of this with an easy to use IDE and

programming pattern. Examples of

what people have done include mak-

ing an unmanned aerial vehicle (UAV)

and weather stations. The limit is

purely your imagination.

The author is associated with the National Instituteof Design

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