Hi everybody and welcome to
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
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.