How to write on DAC 0808 the perfect way?

Forum 2005-2010 (read only) General Exhibition
4

maybe having that division in the ISR is slowing it down too much?
(but i doubt it)

I based mine on this,

http://adrianfreed.com/content/arduino-sketch-high-frequency-precision-sine-wave-tone-sound-synthesis

but using (previously) DAC0808s instead of PWM.

currently i am outputting to 4 DACs (via a ROM chip) and i can send 4 8 bit ROM addresses and calculate for 4 frequencies in a 31.25 khz ISR

Here is the current ISR part of my Scarab bass synth.(now it uses 2x AD7528 instead of 4x DAC0808)

SIGNAL(PWM_INTERRUPT)  //The timer interrupt. 
{
 
  PORTB = PORTB & 11111000;  //reset DAC control bits
  PORTB = PORTB + 2; //Switch to chip 2 DAC 1  
  PORTC = WT1TOP; //send wavetable address to ROM
  PORTA = DAC2Aout;  //send actual wave address byte to ROM
  PORTB = PORTB + 1;  //Switch to chip 2 DAC 2
  //PORTC = WT1TOP;  //send address to ROM [redundant actually]
  PORTA = DAC2Bout;     
  PORTB = PORTB + 1; //Switch to chip 1 DAC 1 
  PORTC = WT0TOP;  //send address to ROM
  PORTA = DAC1Aout;
  PORTB = PORTB + 1;  //Switch to chip 1 DAC 1
  //PORTC = WT0TOP; //send address to ROM
  PORTA = DAC1Bout; 
    
  
  DAC1Aout = (((o1.phase>>16)%LUTsize)^ByteModArray[WT0xor0])- ByteModArray[WT0add];   
  DAC1Bout = ((o1.phase2>>16)%LUTsize)^ByteModArray[WT0xor1];
  DAC2Aout = (((o1.phase3>>16)%LUTsize)^ByteModArray[WT1xor0])- ByteModArray[WT1add];
  DAC2Bout = ((o1.phase4>>16)%LUTsize)^ByteModArray[WT1xor1];     
   
  ByteModArray[6] = DAC2Aout;    //a modulation source
  
  o1.phase += (uint32_t)o1.phase_increment; 
  o1.phase2 += (uint32_t)o1.phase2_increment;
  o1.phase3 += (uint32_t)o1.phase3_increment;
  o1.phase4 += (uint32_t)o1.phase4_increment;
  
  
  if (PORTA <= 1){sync = HIGH;} //pulse once at the start of each cycle  for synth sync
  

if (SYNCCONT > 0){
  
    if (sync == HIGH) {
         o1.phase2 = o1.phase;o1.phase4 = o1.phase3; //for sync         
      sync = LOW;           
    }