/*
        MultiBlinky v1.0
        Blink 2 leds at different frequencies.
        The code is extremely verbose, to make it easier for beginners to
        understand what's happening.

        For future, as this sketch will eat cpu cycles as a starving donkey,
        I will add a microDelay at the end of the loop() function. Calculating
        the amount of microseconds to delay is the tricky part. Feel free to try
        your hand at it.
    */

    /*
        Output leds
    */
    #define LED1 13
    #define LED2 12

    /*
        How many cycles per second (how many cycles per 1000000 microseconds)
        are we doing?
    */
    #define LED1_CYCLES 1
    #define LED2_CYCLES 2

    // these are here for clarity, you can define directly the microseconds/millisecond you need between HIGH/LOW
    uint32_t led1_period = 0;
    uint32_t led2_period = 0;

    // when did we last updated the led
    uint32_t led1_time;
    uint32_t led2_time;

    // state of the led
    char led1_state;
    char led2_state;

    void setup()
    {
        pinMode(LED1, OUTPUT);
        pinMode(LED2, OUTPUT);

        // calculate here the period, so we don't have to do it on each loop() run.
        led1_period = 1000000/LED1_CYCLES;
        led2_period = 1000000/LED2_CYCLES;

        // initialize the system
        led1_state = LOW;
        led2_state = LOW;

        digitalWrite(LED1,LOW);
        digitalWrite(LED2,LOW);

        led1_time = 0;
        led2_time = 0;
    } // end function setup

    void loop()
    {
        /*
            How many microseconds since the board was powered up.
            Arduino's internal timer will reset at some point and
            make our sketch miss a beat or two. If better timing
            is required, go on and use a RTC.
        */
        uint32_t current_time = micros();

        /*
            do we need to do anything to the first led?
        */
        if ( current_time - led1_time > led1_period ) {
            // switch the first led
            led1_time = current_time;
            if ( led1_state == LOW ) {
                led1_state = HIGH;
                digitalWrite(LED1, led1_state);
            } else {
                led1_state = LOW;
                digitalWrite(LED1, led1_state);
            } // end if
        } // end if

        /*
            do we need to do anything to the second led?
        */
        if ( current_time - led2_time > led2_period ) {
            // switch the first led
            led2_time = current_time;
            if ( led2_state == LOW ) {
                led2_state = HIGH;
                digitalWrite(LED2, led2_state);
            } else {
                led2_state = LOW;
                digitalWrite(LED2, led2_state);
            } // end if
        } // end if
    } // end function loop