Raspberry Pi's GPIO

The Raspberry Pi Zero comes with a 40-pin GPIO header. Out of these 40 pins, we can use 26 pins either to read inputs (from sensors) or control outputs. The other pins are power supply pins (5V, 3.3V, and Ground pins):

Raspberry Pi Zero GPIO mapping (source: https://www.raspberrypi.org/documentation/usage/gpio-plus-and-raspi2/README.md)

We can use up to 26 pins of the Raspberry Pi's GPIO to interface appliances and control them. But, there are certain pins that have an alternative function, which will be discussed in the later chapters.

The earlier image shows the mapping of the Raspberry Pi's GPIO pins. The numbers in the circle correspond to the pin numbers on the Raspberry Pi's processor. For example, GPIO pin 2 (second pin from the left on the bottom row) corresponds to the GPIO pin 2 on the Raspberry Pi's processor and not the physical pin location on the GPIO header.

In the beginning, it might be confusing to try and understand the pin mapping. Keep a GPIO pin handout (available for download along with this chapter) for your reference. It takes some time to get used to the GPIO pin mapping of the Raspberry Pi Zero.

The Raspberry Pi Zero's GPIO pins are 3.3V tolerant, that is, if a voltage greater than 3.3V is applied to the pin, it may permanently damage the pin. When set to high, the pins are set to 3.3V and 0V when the pins are set to low.