Direct Port Manipulation Pins

Projects Programming
21 
  // Set up everything to be ready
  const uint8_t sda_mask = (1 << PIND7); // Pin11 (was D5 Pin9)
  const uint8_t clk_mask = (1 << PINB0); // Pin12 (was D6 Pin10)
  uint8_t prev_clk = clk_mask;

  DDRB &= ~(clk_mask);   // clk pin as input
  DDRD &= ~(sda_mask);   // sda pin as input
  PORTD &= ~(sda_mask);  // SDA pin is pulled low or floated up
  // -> we need to set pin low only once.
  //    Toggling is done by setting pin to
  //    input (let float high) or output (pull low).
  //    FV-1 internal pullups are ok (tested).

  uint16_t pos = 0;
  uint8_t curr_byte = algo_buffer[pos];
  uint8_t bit_mask = 0b10000000;
  uint8_t clk_count = 0;

  // Undivided attention for FV-1 requests
  noInterrupts();

  // Notify FV-1 of patch change by toggling the notify pin
  PIND = _BV(4);   // Toggle pin 4
 
  while (clk_count < 37)             // Handle the header
  {
    uint8_t clk = PIND & clk_mask;

    if (!clk && prev_clk) {          // scl went down

      switch (clk_count)
      {
        case 8:
        case 17:
        case 26:
        case 36:
          DDRD  |= sda_mask;         // send ACK - pull sda pin low
          break;
        default:
          DDRD &= ~(sda_mask);       // Release
          break;
      }
      clk_count++;
    }
    prev_clk = clk;
  }
  
  ////Still Freezes Here////