//---------- Constants: ----------

#define PWM_MAX      0xFF00 //PWM full scale
#define FINE_PWM_MAX 0x0100 //fine PWM full scale

//---------- Variables: ----------

static unsigned int Pwm; //current PWM value

//---------- Function prototypes: ----------

#pragma vector = TIMER2_OVF_vect
__interrupt void Pwm_Cycle(void); //timer 2 overflow

//---------- PWM module init: ----------

void Pwm_Init(void)
{
  //timer 2 mode: fast PWM, set OC2 on compare match, CK/1
  TCCR2 = (1 << WGM21) | (1 << WGM20) | (1 << COM21) | (1 << COM20) | (1 << CS20);
  TIFR = (1 << TOV2);    //pending interrupts clear
  TIMSK |= (1 << TOIE2); //overflow interrupt enable
}

//---------- Timer 2 overflow interrupt: ----------

#pragma vector = TIMER2_OVF_vect
__interrupt void Pwm_Cycle(void)
{
  //Delta-Sigma modulator:
  static int Sigma = 0;
  int Delta;
  //quantization:
  if(Sigma > FINE_PWM_MAX)
  {
    Delta = -FINE_PWM_MAX;
    OCR2 = 0xFE - HI(Pwm);
  }
  else
  {
    Delta = 0;
    OCR2 = 0xFF - HI(Pwm);
  }
  //summing:
  Sigma = Sigma + LO(Pwm) + Delta;
}

//---------- Set PWM: ----------

void Pwm_Set(unsigned int v)
{
  if(v > PWM_MAX) v = PWM_MAX;
  Pwm = v;
}

//---------- Get PWM: ----------

unsigned int Pwm_Get(void)
{
  return(Pwm);
}

//----------