Open Music Labs Forums

the full schematic can be found here:
http://wiki.openmusiclabs.com/wiki/Audi ... _schem.png

it uses:
5V , GND, 3.3V - power rails
A0, A1 - pots
A4, A5 - I2C
D5 - codec clock input
D10, D11, D12, D13 - SPI

there are a couple of different ways of doing this. probably the easiest is to put the switch checking in the ISR, and have it update a variable. an example is below

byte switch_position = 0;

ISR(TIMER1_COMPA_vect, ISR_NAKED) { // dont store any registers

  // leave the transfer function at the top as usual
  AudioCodec_data(&left_in, &right_in, left_out, right_out);
  
  // go to the right code depending upon switch position
  if (switch_position == 0) {
    // one set of code here
  }
  else if (switch_position == 1) {
    // second set of code here
  }
  else {
    // last set of code here
  }
  
  // check for new switch position
  // this code assumes a rotary encoder on D2,D3,D4
  switch_position = (PIND >> 2) & 0x07;
  
  // dont forget to return from interrupt
  reti();
}

basically, at the end of the ISR you update the switch_position, and then use that later to decide which set of code to use above. this works well if the switch checking function doesnt take up much time. otherwise it can be placed in the main loop(), but then care has to be taken that switch_position isnt being modified when an interrupt occurs. you would have to declare it volatile, and put cli() and sei() around any code that modifies it.

the switch checking code above uses pins D2,D3,D4, and assumes a binary rotary encoder on them. for an 8 position rotary encoder, this gives values 0 - 7, depending upon the position.