//#define DEBUG

// timing in microseconds
uint32_t timerInterval = 2000;
//uint32_t onTime = 500;
uint8_t percentage = 25;

// struct pulse to make things work 
struct Pulse
{
  uint32_t startTime;
  uint16_t pulseWidth;
  bool isOn;
  bool trigger; 
};

Pulse Pulses [3] {
  {0, 1000, false, false},
  {0, 1500, false, false},
  {0, 2000, false, false}
};

int leds[3] = {3, 5, 6}; 

void setup()
{
  Serial.begin(115200);
  Serial.println(F("Software PWM"));

  for (uint8_t cnt = 0; cnt < 3; cnt++) {
    pinMode(leds[cnt], OUTPUT);
  }
}

void loop()
{
  for (uint8_t cnt = 0; cnt < 3; cnt++) {
    softPWM(cnt);
  }
}

/*
  softPWM
  Create the timebase
  In:
  pulse width
*/
void softPWM(uint8_t index)
{
   if (micros() - Pulses[index].startTime >= timerInterval)
  {
    Pulses[index].startTime = micros();
    Pulses[index].trigger = true; 
  }

  if (Pulses[index].trigger == true) {
    pulse(index); 
  }
}

/*
  Create a pulse
  In:
  index of pwm pin to control
*/
void pulse(uint8_t idx)
{
  if (Pulses[idx].pulseWidth == 0)
  {
    digitalWrite(leds[idx], LOW);
    return;
  }

  if (Pulses[idx].isOn == false)
  {
    digitalWrite(leds[idx], HIGH);
    Pulses[idx].isOn = true;
    Pulses[idx].startTime = micros();

    return;
  }

  if (micros() - Pulses[idx].startTime >= Pulses[idx].pulseWidth)
  {
    digitalWrite(leds[idx], LOW);
    Pulses[idx].isOn = false;
    return;
  }
}