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#define NUM_CHANNELS       2
#define PWM_CHANNEL_PORT   PORTD
#define PWM_CHANNEL_DDR    DDRD

uint16_t SoftPWM_TOP[NUM_CHANNELS];
uint16_t SoftPWM_COMPARE[NUM_CHANNELS];
uint16_t SoftPWM_CURRENT[NUM_CHANNELS];
uint8_t  SoftPWM_PinMasks[NUM_CHANNELS] = {(1 << 0), (1 << 1)};

void SetupPWMTimer(void);
void SetupPWMChannels(void);
void SetupPWMHardware(void);

int main (void)
{
   SetupPWMTimer();
   SetupPWMChannels();
   SetupPWMHardware();

   // Enable interrupts
   sei();

   // Loop forever, PWM taken care of via interrupt
   for (;;);
}

void SetupPWMTimer(void)
{
   // TODO: Set up timer 1 to fire the compare ISR every .1ms
}

void SetupPWMChannels(void)
{
   // Assuming .1ms timer granularity, set first software PWM channel to 100ms period
   SoftPWM_TOP[0] = 1000;

   // Assuming .1ms timer granularity, set second software PWM channel to 50ms period
   SoftPWM_TOP[1] = 500;
   
   // Set first PWM channel to 1/10 duty cycle
   SoftPWM_COMPARE[0] = (SoftPWM_TOP[0] / 10);

   // Set second PWM channel to 1/3 duty cycle
   SoftPWM_COMPARE[1] = (SoftPWM_TOP[1] / 3);
}

void SetupPWMHardware(void)
{
   for (uint8_t Channel = 0; Channel < NUM_CHANNELS; Channel++)
   {   
      // Set PWM channel as output
      PWM_CHANNEL_DDR  |= SoftPWM_PinMasks[Channel];

      // Start with channel ON
      PWM_CHANNEL_PORT |= SoftPWM_PinMasks[Channel];
   }   
}

ISR(TIM1_COMPARE_ISR)
{
   // Loop through each software PWM channel
   for (uint8_t Channel = 0; Channel < NUM_CHANNELS; Channel++)
   {
      // Increment each channel's CURRENT value
      SoftPWM_CURRENT[Channel]++;
      
      // When a channel's CURRENT reaches its COMPARE, clear its output
      if (SoftPWM_CURRENT[Channel] == SoftPWM_COMPARE[Channel])
      {
         PWM_CHANNEL_PORT &= ~SoftPWM_PinMasks[Channel];
      }

      // When a channel's CURRENT reaches its TOP, reset it and set its output
      if (SoftPWM_CURRENT[Channel] == SoftPWM_TOP[Channel])
      {
         PWM_CHANNEL_PORT |= SoftPWM_PinMasks[Channel];
         
         SoftPWM_CURRENT[Channel] = 0;
      }
   }
}