Master RPI.GPIO

Les Pounder goes back to the early days of the Raspberry Pi - and his career with this classic library! -

Python and Raspberry Pi go hand in hand. In the early days of the Pi, there was one Python library that dominated the maker and educational scene: RPi.GPIO. It was quickly adopted by Raspberry Pi as the de facto standard means to interact with the GPIO via Python. In this tutorial, we’ll go back to the early days to learn how this communitycreated project can be used with LEDs and buttons. We’ll also talk a little about how RPi.GPIO came to be.

Project 1: Blinking LEDs

The Hello World of hardware hacking is to blink an LED and we continue this great tradition now. This project is useful to debug hardware and software before moving on to more difficult projects. Our goal is to blink an LED 10 times, and with each change of state (LED on, LED off), we print the state to the Python shell. Doing so, we confirm the code is working as it prints the message. If the LED fails to light, we have a hardware issue.

From the main Raspberry Pi menu, go to Programming and select Thonny. We start the code by importing RPi.GPIO and renaming it to GPIO:

import RPi.GPIO as GPIO

Next use the sleep function from the time module. We use this to control how long the LED is on and off:

from time import sleep

Unlike GPIO Zero, RPi.GPIO requires us to specify the GPIO’s pin mapping. The Raspberry Pi Foundation specifies that Broadcom (BCM) mapping is the standard. This makes for a little confusion as the pins are mapped to a non-sequential series of pins. The alternative board uses physical pin mapping. Pin 1 being the top-left pin nearest the microSD slot. Pin 2 is on the next column of pins. We’ll use BCM mapping:

GPIO.setmode(GPIO.BCM)