Prerequisites & Equipment:
You are going to need the following:
A Raspberry Pi Model B or greater.
A USB WiFi Adapter (Edimax – Wireless 802.11b/g/n nano USB adapter is used here).
An SD Card flashed with the Raspbian OS (Here is a guide if you need)
Access to the Raspberry either via a keyboard and a monitor or remotely.
Installing Wiring Pi:
The Wiring Pi project is used here to switch the GPIO pins high and low. Run the following commands for downloading Wiring Pi and install.
sudo apt-get install git-core
git clone git://git.drogon.net/wiringPi
Fig. 2: Download Wiring Pi On Raspberry Pi
Fig. 3: Installing Wiring Pi On Raspberry Pi
Let’s discuss about using the WiringPi library to turn on and off the first LED (Wiring pin 0). First need to set the pin as an output. Use the “gpio mode 0 out” command to do so. “0” is the wiring pin number and “out” is for output. Now you can use the “gpio write 0 1” command to turn on your LED. “0” is again the pin number and “1” is the status (1 for ON and 0 for OFF). If everything’s fine you should see your LED shining. By using the “gpio write 0 0” command you can turn it off.
If you want to use the actual pin number (GPIO-17) instead of the Wiring Pi number (0 is corresponding to GPIO-17), use the -g flag in your command. Ex: “gpio -g write 17 1” instead of “gpio write 0 1”.
The “gpio read” can be used to read the PIN status. It allows you to be sure of the pin’s status when you can’t see the Output. Using it is as simple as before, just type “gpio read 0” where “0” is the wiring pin number. The command returns the pin’s status (again 1 for ON and 0 for OFF).
Starting Apache web server:
Installing and Configuring of Apache web server is well discussed in previous articles. To start the server is simple as just copy the server files to the apache folder. Download the web server files and extract it to the home folder of Raspberry Pi using Samba webserver are FTP clients.
Copy these files to the apache web server folder which is /var/www and restart the web server. Now our website is alive you can navigate to the website by entering the IP address of the Raspberry Pi.
Controlling the LEDs with PHP:
We now have our apache web server and a Wiring Pi library. The PHP stands for “PHP: Hypertext Preprocessor” which will act as a bridge between these, and it’s a server side scripting language. It means that the PHP code is executed once (each time the page is requested) by the server and cannot be seen by the client. Executing system commands with a PHP code can be done with two different functions: exec (for execute) and system. Firstly, the “system” function. It takes two parameters: “system ( string $command, int $return_var )”.with this function you can execute “gpio mode 0 out” or “gpio write 0 1” commands.
system ( “gpio mode 0 out” );
system ( “gpio write 0 1” );
Then, the “exec” function. This function is making exactly the same work than “system” but it reads and stores what the command printed. It takes three parameters: “exec ( string $command, array $output, int $return_var )”, again $command and $return_var are the same parameters and the only difference is the $output array. Thus, you can use this function if you need what the command prints like with the “gpio read 0” command.
exec ( “gpio read 0”, $status );
print_r ( $status );
Building Graphical Interface:
Fig. 4: Building Raspberry Pi Graphical Interface