/************************************************************************/
/*									*/
/*			Access Dallas 1-Wire Devices			*/
/*                                                                      */
/*              Author: Peter Dannegger                                 */
/*                      danni@specs.de                                  */
/*                                                                      */
/************************************************************************/
#include <util/delay.h>
#include <avr/io.h>
#include <avr/interrupt.h>

#ifndef W1_PIN
#define W1_PIN	PA0
#define W1_IN	PINA
#define W1_OUT	PORTA
#define W1_DDR	DDRA
#endif

uint8_t buff[2];

uint8_t w1_reset(void)
{
  uint8_t err;

  W1_OUT &= ~(1<<W1_PIN);
  W1_DDR |= 1<<W1_PIN;
  _delay_us(480 );			// 480 us
  cli();
  W1_DDR &= ~(1<<W1_PIN);
  _delay_us( 66 );
  err = W1_IN & (1<<W1_PIN);			// no presence detect
  sei();
  _delay_us( 480 - 66 );
  if( (W1_IN & (1<<W1_PIN)) == 0 )		// short circuit
    err = 1;
  return err;
}


uint8_t w1_bit_io( uint8_t b )
{
  cli();
  W1_DDR |= 1<<W1_PIN;
  _delay_us( 1 );
  if( b )
    W1_DDR &= ~(1<<W1_PIN);
 _delay_us( 15 - 1 );
  if( (W1_IN & (1<<W1_PIN)) == 0 )
    b = 0;
  _delay_us( 60 - 15 );
  W1_DDR &= ~(1<<W1_PIN);
  sei();
  return b;
}


uint w1_byte_wr( uint8_t b )
{
  uint8_t i = 8, j;
  do{
    j = w1_bit_io( b & 1 );
    b >>= 1;
    if( j )
      b |= 0x80;
  }while( --i );
  return b;
}


uint w1_byte_rd( void )
{
  return w1_byte_wr( 0xFF );
}


uint8_t w1_rom_search( uint8_t diff, uint8_t idata *id )
{
  uint8_t i, j, next_diff;
  uint8_t b;

  if( w1_reset() )
    return PRESENCE_ERR;			// error, no device found
  w1_byte_wr( SEARCH_ROM );			// ROM search command
  next_diff = LAST_DEVICE;			// unchanged on last device
  i = 8 * 8;					// 8 bytes
  do{
    j = 8;					// 8 bits
    do{
      b = w1_bit_io( 1 );			// read bit
      if( w1_bit_io( 1 ) ){			// read complement bit
	if( b )					// 11
	  return DATA_ERR;			// data error
      }else{
	if( !b ){				// 00 = 2 devices
	  if( diff > i ||
	    ((*id & 1) && diff != i) ){
	    b = 1;				// now 1
	    next_diff = i;			// next pass 0
	  }
	}
      }
      w1_bit_io( b );     			// write bit
      *id >>= 1;
      if( b )					// store bit
	*id |= 0x80;
      i--;
    }while( --j );
    id++;					// next byte
  }while( i );
  return next_diff;				// to continue search
}


void w1_command( uint8_t command, uint8_t idata *id )
{
  uint8_t i;
  w1_reset();
  if( id ){
    w1_byte_wr( MATCH_ROM );			// to a single device
    i = 8;
    do{
      w1_byte_wr( *id );
      id++;
    }while( --i );
  }else{
    w1_byte_wr( SKIP_ROM );			// to all devices
  }
  w1_byte_wr( command );
}