onewire.c

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#include <app.h>

#define PWR_ON_PIN RA1      
#define PWR_ON_DIR TRISA1

#define ID_DQ_PIN RB0       
#define ID_DQ_DIR TRISB0

#define OneWire_PinHI()   TRISB0 = DIR_IN
#define OneWire_PinLO()  { RB0 = 0x00; TRISB0 = DIR_OUT; }
#define W_CELL 4
#define W_INIT 50
#define W_WAIT 2000

BYTE OneWire_GetID(BYTE *buff)
{
   BYTE count, crc;
   ID_DQ_DIR = DIR_IN;

   if(OneWire_Init()==0) 
       return W1_FOUND;

   OneWire_Write(0x33); // read ROM

   for (count=0; count<8; count++)
   {
      buff[count]=OneWire_Read();
   }
    ID_DQ_DIR = DIR_IN;
    
   crc=0; 
   for (count = 0; count < 8; count++) crc = OneWire_Crc8(buff[count], crc);  
   if( crc ) return W1_CRC;
   return W1_OK;
}

BYTE OneWire_Init(void)
{
 WORD w; 
 BYTE is;
   OneWire_PinHI();
   OneWire_PinLO();
   delay_10us(W_INIT);
   OneWire_PinHI();
   w = W_WAIT;
   is=0;
   while(w) 
   {
     if( bittst(gFlags,FN_PCMD)  ) 
                 return 0; // pending command or in process
     --w;
     if( !ID_DQ_PIN ) is=1;
   }
 return is;
}

BYTE OneWire_Read(void)
{
   BYTE n, i_byte;
   for (n=0; n<8; n++)
   {
      RB0=0x00;
      TRISB0=DIR_OUT;
      TRISB0=DIR_IN;
   #asm
      clrwdt
      nop
      nop
   #endasm
      if (RB0)
      {
        i_byte=(i_byte>>1) | 0x80;  // least sig bit first
      }
      else
      {
        i_byte=i_byte >> 1;
      }
      delay_10us(W_CELL);
   }
   return(i_byte);
}

void OneWire_Write(BYTE d)
{
   BYTE n;
   for(n=0; n<8; n++)
   {
      if (d&0x01)
      {
         RB0=0;
         TRISB0=DIR_OUT;        // momentary low
         TRISB0=DIR_IN;
         delay_10us(W_CELL);
      }

      else
      {
          RB0=0;
          TRISB0=DIR_OUT;
           delay_10us(W_CELL);
          TRISB0=DIR_IN;
      }
      d=d>>1;
   }
}

BYTE OneWire_Crc8(BYTE Data, BYTE Accum)
{
BYTE i, f;

   for (i = 0; i < 8; i++)
   {
      f    = 1 & (Data ^ Accum);
      Accum       >>= 1;
      Data        >>= 1;
      if (f) Accum ^= 0x8c;  // b10001100 es la palabra del CRC (x8 + x5 + x4 + 1)
                             //  7..43..0  junto con el 1 aplicado a f.
   }
   return Accum;
}
//*****************************************************************************[ENDL]***************