// call this after you've detected the clock low
char read_byte_ps2() {
  char result=0;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN);

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 1;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 2;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 3;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 4;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 5;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 6;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  result |= input(PS2_DATA_PIN) << 7;

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));

  // parity bit

  while(!input(PS2_CLOCK_PIN));
  while(input(PS2_CLOCK_PIN));  

  // stop bit

  while(!input(PS2_CLOCK_PIN));
  
  return(result);  
}