millis() Blink

millis-blink.c

#include <Arduino.h>

#define PIN_LED 13
#define LED_STATE_SWITCH_INTERVAL 500  // milliseconds between LED state change

unsigned long ledNextStateFlip = 0;
bool ledIsOn = false;

void setup(void) {
    pinMode(PIN_LED, OUTPUT);
    digitalWrite(PIN_LED, LOW);
}

void loop(void) {
    if (millis() > ledNextStateFlip) {
        ledNextStateFlip = millis() + LED_STATE_SWITCH_INTERVAL;
        ledIsOn = !ledIsOn;
        digitalWrite(PIN_LED, ledIsOn);
    }
}