====== Arduino ======
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===== Communication =====

To communicate with the Arduino, the best way I found is to simply use Python. All other methods do not work on all systems, especially on Ubuntu based linux.
I found this solution here : http://shallowsky.com/blog/2011/Oct/16/

When you have loaded the program into your arduino, stop the IDE (only one program can listen on Serial at a time), and launch python. Then, you can listen on Serial port for Arduino using :
<code>
import serial
ser = serial.Serial("/dev/ttyUSB0", 9600)
while True:
   print ser.readline()
</code>
By replacing /dev/ttyUSB0 by your local interface. In my case, the interface was /dev/ttyMAC0 or /dev/ttyMAC1.
You are now free to record your arduino output into a file on your PC or something else, Python is one of the most complete language.
If you get "Cannot open /dev/ttyACM0: Permission denied". or something like that, it means that you are not a member of dialout group.
On Debian base linux, use :
<code>
sudo adduser myuseraccount dialout
</code>
Log out and login, or simply reboot, and you are done with.

===== Sensors =====

==== Light sensors ====

{{ :hardware:computer:photocell_only.jpg?300 |}} (from http://arduinobasics.blogspot.fr/2011/06/arduino-uno-photocell-sensing-light.html)

<code>

int photoRPin = 0; 
int lightLevel;

void setup() {
 Serial.begin(9600);

 lightLevel=analogRead(photoRPin);

}

void loop(){

 lightLevel=analogRead(photoRPin);
 Serial.println(LightLevel);
 delay(50);
}

</code>

==== DHT11 ====

{{ :hardware:computer:fc7xq2lhm8dlw6h.large.gif?400 |}}
(from http://www.instructables.com/id/The-Super-Simple-Arduino-Weather-Web-Server/)

Library can be found here : https://github.com/adafruit/DHT-sensor-library
Example file is provided with the library.