simple blink

ActiveLowLED.h

/*
 *  ActiveLowLED - class for leds that light up when they are grounded
 */
#include <Arduino.h>
#pragma once

class ActiveLowLED {
private:
  const int _pin;
  int _initialized;
  
public:
  
  ActiveLowLED(const int pin) : _pin(pin), _initialized(0) {
    begin();
  }

  void begin() {
    if ( !_initialized ) {
      pinMode(_pin, OUTPUT);   // make it an output
      off();
      _initialized=1;      
    }
  }
  
  void on() {
    digitalWrite(_pin,LOW);
  }
  
  void off() {
    digitalWrite(_pin,HIGH);
  }

  void toggle() {
    digitalWrite(_pin,!digitalRead(_pin));
  }
  
  void blink(int msecOn=100, int msecOff=400) {
    on();
    delay(msecOn);
    off();
    delay(msecOff);
  }

};

sketch.ino

#include "ActiveLowLED.h"

ActiveLowLED led(PC13); // contructor that uses a pinMode call

void setup() {
}

void loop() {
    unsigned x;
    x = 3;
    do {
      led.blink(500,1000);
    } while(--x);
    delay(1000);
    x = 30;
    do {
      led.toggle();
      delay(50);
    } while(--x);
    led.off();
    delay(1000);
}