Отправлено xc164 07 апреля 2004 г. 22:31 В ответ на: цифровые датчики температуры отправлено a_n_h 07 апреля 2004 г. 21:19

#include 
#include 
#include "delay.h"
#include "usart.h"
static	near bit		DS1820 			@ ((unsigned)&PORTB*8+5);
static	near bit		DIR_DS1820 		@ ((unsigned)&TRISB*8+5);
//----------------------------------------------------------------------------
// DS1820 Initialize
// Returns: 1 if DS1820 is present
//          0 if no DS1820 is present
//----------------------------------------------------------------------------
unsigned char DS1820_reset(void) 
{unsigned char present;
  // Reset DS1820...
 DIR_DS1820=0;
 DS1820=0;
 DelayUs(480U);// Keep low signal for at least 480 uSec (reset pulse)
 DIR_DS1820=1;
 DelayUs(60U);// Wait minimum 60 uSec before presence check...(presence pulse)
 // Check if DS1820 present...
 present= (unsigned char) DS1820;
 DelayUs(300U);// Wait minimum 300 uSec
 // return if DS1820 present...
 return !present;
}
//----------------------------------------------------------------------------
// Write a bit to DS1820
//----------------------------------------------------------------------------
void DS1820_wrbit(unsigned char data) 
{// Initiate write slot
 DS1820=0;
 DIR_DS1820=0;
 DS1820=0;
 DelayUs(4U);// Let DS1820 see it...
 DS1820= data >0;         // Put out the bit
 DelayUs(60U);// Wait 60 uSec
 DIR_DS1820=1;
 return;
}
//----------------------------------------------------------------------------
// Read a bit from DS1820
//----------------------------------------------------------------------------
bit DS1820_rdbit(void) 
{static bit data;
 // Initiate read slot
 DS1820=0;
 DIR_DS1820=0;
 DS1820=0;
 DelayUs(2U);// Let DS1820 see it...
 // Let DS1820 see it...
 DIR_DS1820=1;
 DelayUs(10U);
 data=DS1820;	// master samples...
 DelayUs(60U);
 return data;
}
//----------------------------------------------------------------------------
// Write a byte to DS1820
//----------------------------------------------------------------------------
void DS1820_wrbyte(unsigned char c) 
{unsigned char i;
 for (i=0; i<8U; i++) 
	{DS1820_wrbit(c & 0x01); // Send out bit
     c >>=1; 
  }
 return;
}
//----------------------------------------------------------------------------
// Read a byte from DS1820
//----------------------------------------------------------------------------
unsigned char DS1820_rdbyte(void) 
{unsigned char i;
 unsigned char data=0;
 for (i=0; i<8U; i++) 
	{
    data >>=1; // Advance to next bit
    if (DS1820_rdbit())
      data |= 0x80; // It's a '1'
    else
      data &= 0x7F; // It's a '0'
  }
  return data;
}
//----------------------------------------------------------------------------
// Read temperature
// Returns temperature in 0.5 deg resolution.
// (ie. 24.5 deg => 245)
//----------------------------------------------------------------------------
void DS1820_convertt(void) 
{DS1820_reset();          // Reset DS1820
 DS1820_wrbyte(0xCC);     // Skip ROM command
 DS1820_wrbyte(0x44);     // Convert temperature command
 return;
}
 /* ----------------------------------------------------------------------- */
short read_temp(void)
{static unsigned char x;
 static unsigned char crc;
 static unsigned char scpad[9];
 short temp;
/* ------------------------------------------------------------------------
   CRC table for Dallas 8-bit CRC calculations from App. Note #27
   ------------------------------------------------------------------------ */
const unsigned char crc_table[] = {\
     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,\
};
 DS1820_reset();          // Reset DS1820
 DS1820_wrbyte(0xCC);     // Skip ROM command
 DS1820_wrbyte(0xBE);     // Read scratchpad registers
 for( x = 0, crc=0; x < 9; x++ )
   {scpad[x] =  DS1820_rdbyte();
	crc = crc_table[ crc ^ scpad[x] ];
   }
 DS1820_reset();
 if( crc != 0 ) {return -1;}
 temp= ((short)scpad[0]) | ((short)scpad[1])<<8;
 temp >>=1;
 return  temp;
}