multi-blink.c

#include <Arduino.h>

#define PIN_LED_A 13
#define PIN_LED_B 12

#define LED_A_STATE_SWITCH_INTERVAL 500  // milliseconds between LED state change
#define LED_B_STATE_SWITCH_INTERVAL 750  // milliseconds between LED state change

unsigned long ledANextStateFlip = 0, ledBNextStateFlip = 0;
uint8_t ledAIsOn = LOW, ledBIsOn = LOW;

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

void loop(void) {
    if (millis() > ledANextStateFlip) {
        ledANextStateFlip = millis() + LED_A_STATE_SWITCH_INTERVAL;
        ledAIsOn = (ledAIsOn == LOW ? HIGH : LOW);
        digitalWrite(PIN_LED_A, ledAIsOn);
    }
    if (millis() > ledBNextStateFlip) {
        ledBNextStateFlip = millis() + LED_B_STATE_SWITCH_INTERVAL;
        ledBIsOn = (ledBIsOn == LOW ? HIGH : LOW);
        digitalWrite(PIN_LED_B, ledBIsOn);
    }
}