🛠 Bouton poussoir et retour console avec gpiozero

Objectives

Read a push button and control an LED from Python using gpiozero on the Raspberry Pi 3 A+: when_pressed / when_released events, internal pull-up, event loop. gpiozero numbers pins in Broadcom format, just like libgpiod.

Hardware

• Raspberry Pi 3 A+ running Raspberry Pi OS Bookworm, accessed via SSH (no Ethernet: network via WiFi or micro-USB cable in gadget mode)
• Push button, LED + 330 Ω resistor
• Button: GPIO27 (pin 13) to GND (pin 20); LED + 330 Ω: GPIO17 (pin 11) to GND (pin 14)

Complete Code

#!/usr/bin/env python3
# blink_btn.py — sudo apt install python3-gpiozero
from gpiozero import LED, Button   # numérotation Broadcom
from signal import pause

led = LED(17)                       # GPIO17 = broche physique 11
btn = Button(27, pull_up=True)      # GPIO27 = broche 13, repos à l'état haut

def on_press:
    print("Bouton pressé — la LED clignote")
    led.blink(on_time=0.2, off_time=0.2)

def on_release:
    print("Bouton relâché — LED éteinte")
    led.off

btn.when_pressed = on_press
btn.when_released = on_release

print("3A+ prêt (4x Cortex-A53 @ 1,4 GHz) — appuyez sur le bouton")
pause   # garde la boucle d'événements alive

sudo apt install -y python3-gpiozero
python3 blink_btn.py

Expected Verification

The console displays "3A+ ready"; each time the button is pressed, the LED starts blinking and a message is displayed; when released, the LED turns off. Ctrl+C exits cleanly.

Common Errors

• Wiring the button to 3.3 V instead of GND without understanding pull-ups: with pull_up=True, the idle state is high and pressing the button results in a low state.
• Forgetting pause: the script terminates immediately and the button never responds.
• Connecting GPIO27 directly to 5 V: the 3 A+ logic operates at 3.3 V, and 5 V can damage the SoC.
• Confusing pin 13 (GPIO27) and pin 11 (GPIO17) on the 40-pin connector.