🛠 Faire clignoter une LED via le GPIO

Objectives

Blink an external LED from an ODROID-C2 GPIO pin using Hardkernel's wiringPi port (the wiring-odroid package), using the physical pin numbering of the J2 connector — the safest mode on a non-Raspberry Pi board.

Hardware

• ODROID-C2 (Amlogic S905, 2 GB) powered by 5 V / 2 A (2.5x0.8 mm jack preferred)
• Armbian, Arch Linux ARM, or DietPi image
• LED + 330 ohm resistor, breadboard, jumper wires
• Wiring: physical pin 7 (GPIO output) -> resistor -> LED -> GND; 3.3 V logic only across the entire J2 connector
• wiring-odroid package (confirmed on Arch Linux ARM; on vendor images, the wiringPi library is preinstalled)

Complete code

/* blink.c — compiler sur la carte : gcc blink.c -lwiringPi -o blink */
#include <wiringPi.h>
#include <stdio.h>

#define LED 7   /* broche physique 7 du connecteur J2 */

int main(void) {
    if (wiringPiSetupPhys == -1) { perror("wiringPiSetupPhys"); return 1; }
    pinMode(LED, OUTPUT);
    for (;;) {
        digitalWrite(LED, HIGH);
        delay(500);
        digitalWrite(LED, LOW);
        delay(500);
    }
}

Expected verification

After sudo ./blink, the LED blinks with a one-second period. The user blue LED (c2:blue:alive in mainline, blue:heartbeat on vendor images) continues to blink in a heartbeat pattern: it serves as an independent system indicator. >

Common errors

• Forgetting the resistor: the GPIOs are 3.3 V and the current per pin is limited (wiki value not reconfirmed).
• Using the default wiringPi numbering (Pi-like BCM mode) instead of wiringPiSetupPhys: the indices do not match the ODROID-C2.
• Missing wiring-odroid package on mainline Armbian: in this case, control the blue LED via /sys/class/leds/*blue*/brightness, or install wiring-odroid on Arch Linux ARM.
• Undersized power supply: a micro-USB phone charger causes reboots (brown-out).