Introducing GPIO pins

Most of you may know where GPIO pins are located on the Raspberry Pi. If not, the following illustration will make it clear:

The following is a top view of the Raspberry Pi B+ board, which will help you see the components even more clearly:

The following diagram of the GPIO pins gives information about the naming convention and the function of each of the pins:

Note

Note that the GPIO pins of Raspberry Pi B+ and Pi 2 are the same.

As you can see from the preceding diagram, there are four power pins, two for 3.3V and two for 5V, 8 ground pins distributed across the rail, 26 GPIO pins—some of which also provide protocols such as UART, SPI, PCM, PWM, I2C—and two pins reserved for accessing the EEPROM via I2C.

GPIO pins can be ON or OFF and HIGH or LOW. When a 3.3V pin is high, it outputs 3.3V, and when it is low, it outputs 0V. A GPIO pin can act as an input as well as an output but not both at the same time. To use it as an output is as simple as setting the pin state to ON...