/************************************************************

*18B20驅動程序，DQ為數據口，接于P2.1

*11.0592M晶振，上拉4.7k電阻

*Author:fyb

*2005-3-25 11:23，OK!

*************************************************************/
#include"at89x52.h" 

#define uchar unsigned char

#define uint  unsigned int



sbit dq = P1^7;

bit  flag;

uint Temperature;

uchar temp_buff[9]; //存儲讀取的字節，read scratchpad為9字節，read rom ID為8字節

uchar id_buff[8];

uchar *p;

uchar crc_data;

uchar code CrcTable [256]={

0,  94, 188,  226,  97,  63,  221,  131,  194,  156,  126,  32,  163,  253,  31,  65,

157,  195,  33,  127,  252,  162,  64,  30,  95,  1,  227,  189,  62,  96,  130,  220,

35,  125,  159,  193,  66,  28,  254,  160,  225,  191,  93,  3,  128,  222,  60,  98,

190,  224,  2,  92,  223,  129,  99,  61,  124,  34,  192,  158,  29,  67,  161,  255,

70,  24,  250,  164,  39,  121,  155,  197,  132,  218,  56,  102,  229,  187,  89,  7,

219,  133, 103,  57,  186,  228,  6,  88,  25,  71,  165,  251,  120,  38,  196,  154,

101,  59, 217,  135,  4,  90,  184,  230,  167,  249,  27,  69,  198,  152,  122,  36,

248,  166, 68,  26,  153,  199,  37,  123,  58,  100,  134,  216,  91,  5,  231,  185,

140,  210, 48,  110,  237,  179,  81,  15,  78,  16,  242,  172,  47,  113,  147,  205,

17,  79,  173,  243,  112,  46,  204,  146,  211,  141,  111,  49,  178,  236,  14,  80,

175,  241, 19,  77,  206,  144,  114,  44,  109,  51,  209,  143,  12,  82,  176,  238,

50,  108,  142,  208,  83,  13,  239,  177,  240,  174,  76,  18,  145,  207,  45,  115,

202,  148, 118,  40,  171,  245,  23,  73,  8,  86,  180,  234,  105,  55,  213, 139,

87,  9,  235,  181,  54,  104,  138,  212,  149,  203,  41,  119,  244,  170,  72,  22,

233,  183,  85,  11,  136,  214,  52,  106,  43,  117,  151,  201,  74,  20,  246,  168,

116,  42,  200,  150,  21,  75,  169,  247,  182,  232,  10,  84,  215,  137,  107,  53};

//

/************************************************************

*Function:延時處理

*parameter:

*Return:

*Modify:

*************************************************************/

void TempDelay (uchar us)

{

  while(us--);

}

/************************************************************

*Function:18B20初始化

*parameter:

*Return:

*Modify:

*************************************************************/

void Init18b20 (void)

{

dq=1;

_nop_();

dq=0;

TempDelay(86);   //delay 530 uS//80

_nop_();

dq=1;

TempDelay(14);   //delay 100 uS//14

_nop_();

_nop_();

_nop_();



if(dq==0)

  flag = 1;   //detect 1820 success!

else

  flag = 0;    //detect 1820 fail!

TempDelay(20);       //20

_nop_();

_nop_();

dq = 1;

}

/************************************************************

*Function:向18B20寫入一個字節

*parameter:

*Return:

*Modify:

*************************************************************/

void WriteByte (uchar wr)  //單字節寫入

{

uchar i;

for (i=0;i<8;i++)

{

  dq = 0;

  _nop_();

  dq=wr&0x01;

  TempDelay(5);   //delay 45 uS //5

  _nop_();

  _nop_();

  dq=1;

  wr >>= 1;

}

}

/************************************************************

*Function:讀18B20的一個字節

*parameter:

*Return:

*Modify:

*************************************************************/

uchar ReadByte (void)     //讀取單字節

{

uchar i,u=0;

for(i=0;i<8;i++)

{

  dq = 0;

  u >>= 1;

  dq = 1;

  if(dq==1)

  u |= 0x80;

  TempDelay (4);

  _nop_();

}

return(u);

}

/************************************************************

*Function:讀18B20

*parameter:

*Return:

*Modify:

*************************************************************/

void read_bytes (uchar j)

{

  uchar i;

  for(i=0;i  {

    *p = ReadByte();

    p++;

  }

}

/************************************************************

*Function:CRC校驗

*parameter:

*Return:

*Modify:

*************************************************************/

uchar CRC (uchar j)

{

    uchar i,crc_data=0;

   for(i=0;i     crc_data = CrcTable[crc_data^temp_buff[i]];

    return (crc_data);

}

/************************************************************

*Function:讀取溫度

*parameter:

*Return:

*Modify:

*************************************************************/

void GemTemp (void)

{

   read_bytes (9);

   if (CRC(9)==0) //校驗正確

   {

     Temperature = temp_buff[1]*0x100 + temp_buff[0];

//     Temperature *= 0.625;

  Temperature /= 16;

  TempDelay(1);

    }

}

/************************************************************

*Function:內部配置

*parameter:

*Return:

*Modify:

*************************************************************/

void Config18b20 (void)  //重新配置報警限定值和分辨率

{

     Init18b20();

     WriteByte(0xcc);  //skip rom

     WriteByte(0x4e);  //write scratchpad

     WriteByte(0x19);  //上限

     WriteByte(0x1a);  //下限

     WriteByte(0x7f);     //set 11 bit (0.125)

     Init18b20();

     WriteByte(0xcc);  //skip rom

     WriteByte(0x48);  //保存設定值

     Init18b20();

     WriteByte(0xcc);  //skip rom

     WriteByte(0xb8);  //回調設定值

}

/************************************************************

*Function:讀18B20ID

*parameter:

*Return:

*Modify:

*************************************************************/

void ReadID (void)//讀取器件 id

{

Init18b20();

WriteByte(0x33);  //read rom

read_bytes(8);

}

/************************************************************

*Function:18B20ID全處理

*parameter:

*Return:

*Modify:

*************************************************************/

void TemperatuerResult(void)

{

   p = id_buff;

   ReadID();

   Config18b20();

Init18b20 ();

WriteByte(0xcc);   //skip rom

WriteByte(0x44);   //Temperature convert

Init18b20 ();

WriteByte(0xcc);   //skip rom

WriteByte(0xbe);   //read Temperature

p = temp_buff;

GemTemp();

}