🛠 Lire un bouton poussoir et afficher dans la console

Objectives

Read the state of a push button on the 40-pin connector and display a message in the console on each press, using gpiomon (libgpiod) which waits for edges on a GPIO line. We reuse pin 7 (GPIO1_D6 = gpiochip1, line 30) already wired in the LED tutorial: remove the LED before starting.

Hardware

• Powered Orange Pi 5 Plus (Type-C side of the Ethernet ports, 5 V / 4 A)
• 1 push button + 1 10 kΩ resistor (pull-up to 3.3 V)
• Jumper cables, terminal access
• gpiod package installed (sudo apt install -y gpiod)

Complete code

# Attente d'un seul appui (front descendant : repos au niveau haut grâce au pull-up)
sudo gpiomon --num-events=1 --falling-edge gpio1 30

# Boucle complète : un message par appui, anti-rebond 50 ms
while sudo gpiomon --num-events=1 --falling-edge \
      --debounce-edge-period 50000000 gpio1 30 >/dev/null; do
    echo "Bouton pressé à $(date +%T)"
done

Expected verification

gpiomon blocks and then displays a line like event: 1 falling edge on the first press. With the loop, each press prints "Button pressed" with the time; without debouncing, a single press can trigger 2 to 5 events (mechanical contact bounce).

Common errors

• No pull-up resistor: the line floats, gpiomon triggers continuously at the slightest noise. An internal pull-up resistor can be requested via libgpiod bias options, but an external 10 kΩ pull-up is more robust for beginners.
• Inverted edge: with a pull-up + button to ground, pressing produces a falling edge (--falling-edge), not a rising one.
• Wrong line: pin 7 = line 30 of gpiochip1 (GPIO1_D6), not line 7 nor gpiochip0.
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