Open Music Labs Forums

I am getting quite a bit of zippering/ strange audio distortion
on the sketches which use pots to control delay time. This makes the sketches pretty much unusable in any case where I want to change values in real-time.

Mark of Open Music Labs had told me in an email that he knew the cause of this problem and had a workaround for it
which involved changing the oversampling on the ADC channels.

So..I was wondering if we could get his added to the forum or to the sketch library?

thanks

give this a try
it still has a bit of noise
but its greatly reduced

// timer1 interrupt routine - all data processed here
ISR(TIMER1_COMPA_vect, ISR_NAKED) { // dont store any registers

  // &'s are necessary on data_in variables
  AudioCodec_data(&left_in, &right_in, left_out, right_out);
  
  // pass left input to right output
  right_out = left_in;
  delaymem[location++] = left_in; // post increment location to go to next memory location
  // check if location has gotten bigger than buffer size
  if (location >= SIZE) {
    location = 0; // reset location
  }
  //calculate delay time
  unsigned int temp = location - currentdelay;
  if (temp >= SIZE) {
    temp += SIZE;
  }
  //fetch data from buffer and put it into output register
  left_out = delaymem[temp];

  // & is required before adc variable
  AudioCodec_ADC(&mod0_value);

  // scale ADC value to match buffer size
  // note the use of the fancy fast math function
  // you can read about these in the readme file
  unsigned int scale = SIZE;
  MultiU16X16toH16(desireddelay, mod0_value, scale);
  // sowly sweep delay time to reduce zipper noise
  if (currentdelay == desireddelay);
  else if (currentdelay < desireddelay) {
    currentdelay++;
  }
  else {
    currentdelay--;
  }

  reti(); // dont forget to return from the interrupt
}