PWM video code analysis and explanation

void loop()

{

    static unsigned char head = 0;

    static unsigned long lastTick = timer0_millis;

    unsigned int i, j;

    for (i = 0; i < ledNum; ++i) // Turn on the light first, then turn it off when the duty cycle reaches the switching point

    {

        if (ledPwm[i] == 0)

            continue;

        digitalWrite(leds[i], LOW);

    }

    ledPwm[head] = initPwm; // The water drop head is the brightest

    for (i = 0; i < maxPwm; ++i) // Here is the PWM program for digital port simulation

    {

        for (j = 0; j < ledNum; ++j)

        {

            if (i == ledPwm[j])

                digitalWrite(leds[j], HIGH);

        }

        delayMicroseconds(1);

    }

    // If the delay time has not expired, jump out first without moving the water droplets. 

    if (timer0_millis - lastTick < delayMs) // Since it uses a digital port to simulate PWM, the program has to run non-stop, so delay() cannot be used to delay, otherwise it will get stuck.

        return;

    lastTick = timer0_millis;

    for (i = 0; i < ledNum; ++i) // Process the brightness of each light

    {

        ledPwm[i] = ledPwm[i] * deltaPercent / 100;

        if (ledPwm[i] <= deltaPwm){ ledPwm[i] = 0; }           

        else                      { ledPwm[i] -= deltaPwm; }

        if (i == head){ ledPwm[i] = initPwm; }            

    }

    head = (head + 1) % ledNum; // Move the water dropper

}

Full version of LED "Meteor Shower" effect

Summarize:

1. We understand how PWM is implemented

2. LEDs will "deceive" our eyes at different frequencies. This is a common idea when playing with microcontrollers.

3. By analyzing the LED "meteor shower", we found that it is actually implemented using some simple processing methods and is not as complicated as we imagined.

4. There is a simple algorithm in LED "Meteor Shower". The algorithm is independent of the microcontroller and can also be implemented on other platforms (51, STM32, etc.). At the same time, the algorithm is also the soul of a program.