Hilfe zu DS18S20

// ds18s20 support (data line at PD4, parasite power from port)

static void DS1820_Init(void)

{

  PORTD= (byte)~(1u<<4); // activate internal pullups to avoid floating input pins but..

                    // not for the data line, have external pullup of 4.7k required for DS1820

  // DDRD is initial input (output only if we send or are strong pullup mode)

}

// reset, returns true if any 1-wire device present, false elsewhere

static bool DS1820_Reset(void)

{

  PORTD |= (1u<<4); // prepare by setting port to high

  DDRD  |= (1u<<4); // port now output

  PORTD &= ~(1u<<4); // setting port to low (reset impulse)

  _delay_us(500); // min 480 us 

  DDRD  &= ~(1u<<4); // port now input

  _delay_us(10); // 15-60 us until DS1820 pulls down the bus (and here the pullup resistor must bring the bus from low to high)

  // high detected check (sample some pulses to be independent of spikes)

  byte b;

  for (b= 0; b < 10; ++b) {

    if ((PIND & (1u<<4)) == 0) {

      TRACE("no high after reset (wire problem - no pullup)");

      return false;

    }

  }

  // now wait for the down pulse from DS1820 (typ 25 us, counter=15 with above wait of 10 us)

  for (b= 0; b < 60; ++b) {

    if ((PIND & (1u<<4)) == 0)

      break;

    _delay_us(1);

  }

  if (b==60) {

    TRACE("no down-pulse after reset (no DS1820 present)");

    return false;

  }

  // count the down pulse length

  for (b= 0; b < 255; ++b) {

    if ((PIND & (1u<<4)) != 0)

      break;

    _delay_us(1);

  }

  // test if length meets requirements (typ 80-82 us)

  if (b < 60 || b > 240) {

    TRACE("down pulse length wrong");

    return false;

  }

  return true;

}

int main(void)

{

  AVR_Init();

  LCD_Init();

  LCD_Start();

  LCD_Clear();

  DS1820_Init();

  for (;;) {

    if (DS1820_Reset())

      TRACE("ds1820");

    else

      TRACE("no ds1820");

    waitforKey();

    _delay_ms(100);

  }

}

// AVR: friendly typedef for a fundamental data type

// policy:

//   use byte, int, char for normal programming, 

//   but uint16_t etc for network data access (int etc may be > 16 bits on some procs)

typedef unsigned char byte;

typedef unsigned int uint;

#if 1

# define TRACE(x) Trace_LCD_P(PSTR(x))

#else

# define TRACE(x)

#endif

// ds18s20 support (data line at PD4, parasite power from port)

static void DS1820_Init(void)

{

  PORTD= (byte)~(1u<<4); // activate internal pullups to avoid floating input pins but..

                    // not for the data line, have external pullup of 4.7k required for DS1820

  // DDRD is initial input (output only if we send or are strong pullup mode)

}

// reset, returns true if any 1-wire device present, false elsewhere

static bool DS1820_Reset(void)

{

  PORTD &= (byte)~(1u<<4); // ensure low value, if we switch port to output (is this paranoia?)

  DDRD  |= (1u<<4); // port now output (reset impulse - low value)

  _delay_us(500); // min 480 us

  DDRD  &= ~(1u<<4); // port now input again

  _delay_us(10); // 15-60 us until DS1820 pulls down the bus (and here the pullup resistor must bring the bus from low to high)

  // high detected check (sample some pulses to be independent of spikes)

  byte b;

  for (b= 0; b < 10; ++b) {

    if ((PIND & (1u<<4)) == 0) {

      TRACE("no high after reset (wire problem - no pullup)");

      return false;

    }

  }

  // now wait for the down pulse from DS1820 (typ 25 us, counter=15 with above wait of 10 us)

  for (b= 0; b < 60; ++b) {

    if ((PIND & (1u<<4)) == 0)

      break;

    _delay_us(1);

  }

  if (b==60) {

    TRACE("no down-pulse after reset (no DS1820 present)");

    return false;

  }

  // count the down pulse length

  for (b= 0; b < 255; ++b) {

    if ((PIND & (1u<<4)) != 0)

      break;

    _delay_us(1);

  }

  // test if length meets requirements (typ 80-82 us)

  if (b < 60 || b > 240) {

    TRACE("down pulse length wrong");

    return false;

  }

  _delay_us(500); // reset time slot must be min 480 us

  return true;

}

// write "0" slot (every write slot must be min 60 us + 1 us recovery time)

static inline void DS1820_Write0(void)

{

  DDRD  |= (1u<<4); // port now output (low value)

  _delay_us(60); // min 60 us

  DDRD  &= ~(1u<<4); // port now input again

  _delay_us(2); // min 1 us, complete the time slot by recovery time

}

// write "1" slot

static inline void DS1820_Write1(void)

{

  DDRD  |= (1u<<4); // port now output (low value)

  _delay_us(2); // min >1 us

  DDRD  &= ~(1u<<4); // port now input again

  _delay_us(60); // min 60 us, complete the time slot by recovery time

}

// read bit "0/1" slot

static inline bool DS1820_Read(void)

{

  DDRD  |= (1u<<4); // port now output (low value)

  _delay_us(2); // min >1 us

  DDRD  &= ~(1u<<4); // port now input again

  _delay_us(10-2); // start sampling the bit, 10 us after initiating transfer

  // sample the line, 16 times

  byte h= 0;

  for (byte n= 0; n < 16; ++n) {

    if ((PIND & (1u<<4)) != 0)

      ++h;

  }

  _delay_us(60); // min 60 us, complete the time slot by recovery time

  // test is this a high or low ?

  if (h==0)

    return false;

  if (h==16)

    return true;

  TRACE("Read unsure!");

  return h > 8;

}

static void DS1820_WriteByte(byte b)

{

  for (byte n=0; n < 8; ++n) {

    if (b & 1)

      DS1820_Write1();

    else

      DS1820_Write0();

    b= b >> 1u;

  }

}

static byte DS1820_ReadByte(void)

{

  byte b= 0;

  for (byte n=0; n < 8; ++n) {

    b= b >> 1;

    if (DS1820_Read())

      b |= 0x80;

  }

  return b;

}

int main(void)

{

  AVR_Init();

  LCD_Init();

  LCD_Start();

  LCD_Clear();

  DS1820_Init();

  for (;;) {

    if (!DS1820_Reset())

      TRACE("no ds1820");

    DS1820_WriteByte(0x33); // read rom cmd

    byte romcode[8];

    for (byte n= 0; n < 8; ++n)

      romcode[n]= DS1820_ReadByte();

    Print_LCD("\n");

    for (byte n= 0; n < 8; ++n) {

      char buf[80];

      ultoa(romcode[n], buf, 16);

      Print_LCD(buf);

      Print_LCD(" ");

    }

    byte crc= 0;

    for (byte n= 0; n < 8; ++n)

      crc= _crc_ibutton_update(crc, romcode[n]);

    if (crc == 0)

      Print_LCD("- crc ok");

    else

      Print_LCD("crc fail:");

    waitforKey();

    _delay_ms(100);

  }

}

//code

#define TIMESLOT   70

#define RESET_PULSE  480

//weiterer code

//-----------------------------------------------------------------------------

// Generate a 1-Wire reset, return 1 if no presence detect was found,

// return 0 otherwise.

// (NOTE: Does not handle alarm presence from DS2404/DS1994)

//

// Bus hängt am Pin PC3 

//

uint8_t OWTouchReset(void)

{

  uint8_t result;

  DDRC |= (1<<DDC3);   // Port-PIN als Ausgang konfigureren

  PORTC &= ~(1<<PC3); // Drives DQ low

  _delay_us(RESET_PULSE);

  PORTC |=  (1<<PC3); // Releases the bus

  _delay_us(TIMESLOT);

  DDRC &= ~(1<<DDC3);   // Port-PIN als Eingang konfigureren

  result = PINC & (1<<PC3); // Sample for presence pulse from slave

  _delay_us(RESET_PULSE-TIMESLOT);

  return result; // Return sample presence pulse result

}

i=OWTouchReset();