another Arduino tutorial video

supported by RS components.

Today we are going to look at

the Arduino WiFi shield

It's a module that you can connect to your

Arduino and that allows

the Arduino board to connect to

a WiFi network

and then connect to the internet

and we can make

all sorts of devices

using this tool

Today,

the example

I'm going to show you

is a simple lamp

that changes color depending on

messages posted on twitter

If somebody posts a twitter message

that begins with the ashtag

#ArduinoRGB

and then followed by a color

represented as a six digit

hexadecimal number

This is the way for example,

that colors are represents in

HTML pages.

The six digits represents

the amount of Red, Green and Blue

that goes into the color.

The first two digits represent

the Red, the second two the green

and the last two the blue

So

what the Arduino is going to do is to connect

to twitter, launch a search

and it will search for all

the messages that contain this hashtag

and once it finds one

it will search for the number

then decode the number into the amount

of color that will be represented

on the RGB LED

that you see here on the circuit.

Let's have a look at the circuit

Here, we have an Arduino UNO

with a WiFi module

mounted on top of it

t and very simply,

we took a small RGB LED

and we connected three resistors

The three resistors go to pin 3, 5 and 6

that are PWM pins

So these pins are able to control

the brightness

of each individual channel

in the RGB LED.

The module that you see on the top here

is the Arduino WiFi shield.

The Arduino WiFi shield is actually quite

an interesting device

It's made by this large chip

in the middle

it's a 32 bit micro controller

that contains the whole software

needed to process the WiFi messages

and connect to the internet and

provide you with the whole

network keys tag

And it speaks to this little

square module in the corner

that is the wireless part

that communicates with the WiFi network

So, by using

a powerful processor onboard

of the shield

we can save code space

we can save memory

on the main Arduino board.

So, let's have a look at the code:

In order to use the

Arduino WiFi shield we include the WiFi

WiFi library and then we have

at the beginning, a couple of strings

that represent the name of

the wireless network we are connected to

At this moment

we are connected to a network

that doesn't require a password

so the next parameter

will contain just the word "password

that we are not going to use

Then we have three pins

pin_r, pin_g and pin_b

These variables contain

the number of the pins

the LED is connected to.

Then we have the constant

maxTweets that indicates the amoun

of tweets returned by a search

I have to specify that most

of the code you see here comes from

an example that was written by

Limor Fried for the Adafruit

of things printer

I took this code

and I removed the part that prints

to the actual printer

and I replaced it with a

a simple piece of code that

parses the information

There are other parameters that

indicate the frequency used by Arduino

to connect to twitter

in this case we are connecting every

ten seconds and the time out

the maximum number of times we will try

to connect to the server

to connect to the server

and the timeout -

the maximum time we will wait for

the response of the server.

There are a number of internal parameters

maybe too long to explain right now.

So, we create a WiFi client

we specify the server name,

we specify the queryString -

in this case "ArduinoRGB.

We can skip the rest of the code

so that I can show you how easy it is

to connect to the WiFi

Here we check if the WiFi

is actually mounted on the board

then we check it we are connected

we just say WiFi.begin(ssid)

If I need to specify a password

I can put it here after this code

as you can see in the comment

and we can specify user ID and password.

Then we wait for ten seconds

That should be enough for a connection

and this is going to try and retry

to connect to the WiFi network until we connect.

printWifiStatus will tell us:

ok you are connected, this is your

IP number

this is the network you are connected to, etc

Then during the loop

what we are going to do is

to create a connection to the server

We are going to send a request

this code I'm highlighting now

is the one that sends the request

to the server

and then later on

once the data

- once the data has been received

it says here "processing results..."

We go to this function called jsonParse

jsonParse() does quite a lot of

work in processing the data that comes

from the server and what is interesting

for us is here.

If the length of the message

that we receive is less than 20

that means the message is short

enough to be

so I'm going to decode the color

print out the values

that we are going to send to the LED

I'm using analogWrite to set

the color of each channel of the LED

Then we are going to print

some more debugging information

if we want to

know if everything worked out.

Then we are going to reset the time

start so that we can

check again in ten seconds.

Here I am going to bring in

the debugging message window.

"Davide can you please send a tweet"

Our friend Davide will send a tweet

with a color - let's say

FF0000, that represents the full red color.

Now the tweet has been sent

it is going to take a few seconds

before twitter stores the tweet

and makes it available in the search.

At the moment you can see the log

is just saying

it is waiting for results

there is no new results, pausing...

at the moment it it connecting

every 10 seconds.

Ah! the message has been received

and you can see that there was a message

#ArduinoRGB FF0000 and

our LED is now RED.

Based on this code

you can develop

all sorts of other applications.

This could be a lamp or for example

a system to water your plants

in the garden or this could be the

heating in your mountain

home or something like that.

So we could attach almost anything

to this Arduino and make it

WiFi-enabled.

Thank you for joining us

and I hope you enjoy this project.

And remember:

build it, hack it

and share it, because Arduino is you.