🛠 Lire un bouton poussoir en Python avec python3-libgpiod

Objectives

Wire a push button to the 40-pin connector of the ROCK 3B and display each press in the console using python3-libgpiod, utilizing interrupt events (rising edge) rather than polling in a loop. This is the first Python script in the series: it serves as a foundation for sensor and IoT tutorials.

Hardware

• Radxa ROCK 3B running Radxa OS, USB-C PD 12 V / 2 A power supply
• 1 push button, 1 10 kΩ resistor (pull-up to 3.3 V), Dupont cables
• sudo apt install python3-gpiod gpiod

Complete Code

#!/usr/bin/env python3
"""Bouton sur le connecteur 40 broches — affiche les appuis (ROCK 3B).
 Résolvez CHIP/LINE avec `gpiofind PIN_11` sur VOTRE image : les numéros
 diffèrent entre noyau constructeur (Radxa) et noyau mainline >= 6.11."""
from gpiod import Chip, LineRequest

CHIP, LINE = "gpiochip3", 1   # exemple GPIO3_A1 derrière PIN_11 — CONFIRMER

with Chip(CHIP) as chip:
    req = chip.request_lines(
        consumer="rock3b-demo",
        config={LINE: LineRequest.REQUEST_INPUT},
    )
    print("appui attendu (front montant), Ctrl-C pour quitter")
    while True:
        for ev in req.event_wait(timeout_ms=None):
            e = req.event_get
            if e and e.event_type == 1 and e.line == LINE:  # RISING_EDGE
                print("bouton pressé")

Expected Verification

sudo python3 bouton.py starts without errors; each press (rising edge) displays "button pressed". Ctrl-C releases the line cleanly. With a hardware pull-up + button to ground, the idle state is 1 and the pressed state is 0: if nothing is displayed, swap the button/cable or test sudo gpioget $(gpiofind PIN_11) with a logic multimeter.

Common Errors

• Copying CHIP/LINE numbers from another tutorial: Radxa's GPIOD documentation insists — always resolve with gpiofind PIN_xx, as the mapping changes between the manufacturer image and mainline.
• python3-libgpiod API: recent versions (libgpiod v2) use request_lines(config=...), older ones use line.request(consumer=..., type=...) — adapt according to the installed Debian package.
• Leaving the pin floating without a pull: the state oscillates randomly; a 10 kΩ hardware pull-up to 3.3 V is the most educational approach.
• Confusing the physical connector pin with the libgpiod line: only the line number matters to the script.
• Forgetting the common ground between the breadboard and the board: the rising edge never arrives cleanly.