In my earlier blogs I have shown you how to install the OS and use it. Now we are ready to start building the projects. To do so we first need to understand what each pin does. The diagram below shows raspberry pi 2 pinouts and what each pins can do.
Raspberry Pi 2 pinout figure 1
In order to understand pin number, make sure to have your pi oriented as shown in the figure. Now look at the centre two columns on the chart. These shows the Physical Pin number. The outer two columns of the chart show you the bcm numbering. The numbering system that you use depends on how you configure things in the software. There are 2 numbering sachems. One is BCM(Broadcom)
which is more common and will be using for most of the projects and the other is WiringPi. The picture below shows WiringPi numbering.
Also you can notice that some of the pins are multi-purpose. For example pin3 and 5 can be GPIO pins, or they can be configured for I2C. Similarly, 8 and 10 can be General purpose or can be Tx and Rx. Also note that the GPIO pins are analogous to your digital input/output pins on Arduino.
Raspberry Pi 2 pinout figure 2