volatile unsigned int Acc, Jump;
unsigned int Freq = 100 ;

void SetupDDS () {
  // Enable 64 MHz PLL and use as source for Timer1
  PLLCSR = 1<<PCKE | 1<<PLLE;

  // Set up Timer/Counter1 for PWM output
  TIMSK = 0;                               // Timer interrupts OFF
  TCCR1 = 1<<PWM1A | 2<<COM1A0 | 1<<CS10;  // PWM A, clear on match, 1:1 prescale
  pinMode(1, OUTPUT);                      // Enable PWM output pin

  // Set up Timer/Counter0 for 20kHz interrupt to output samples.
  TCCR0A = 3<<WGM00;                       // Fast PWM
  TCCR0B = 1<<WGM02 | 2<<CS00;             // 1/8 prescale
  TIMSK = 1<<OCIE0A;                       // Enable compare match, disable overflow
  OCR0A = 60;                              // Divide by 61
}

ISR(TIMER0_COMPA_vect) {
  //Square () 
  Acc = Acc + Jump;
  int8_t temp = Acc>>8;
  OCR1A = temp>>7;

// void Sawtooth () {
//   Acc = Acc + Jump;
//   OCR1A = Acc >> 8;
// }
}
void setup() {
  SetupDDS ();
  Jump = Freq*4;
  GIMSK = 1<<PCIE;            // Enable interrupt
  GIFR = 1<<PCIF;  
}

void loop() {
  // put your main code here, to run repeatedly:

}