ds18b20.c

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/*
  CodeVisionAVR C Compiler
  (C) 1998-2005 Pavel Haiduc, HP InfoTech S.R.L.

  Dallas Semiconductor DS18B20 1 Wire bus temperature sensor functions
*/

#include <delay.h>
#include <ds18b20.h>

struct __ds18b20_scratch_pad_struct __ds18b20_scratch_pad;

// temp. conversion time [ms] depending on the resolution
static flash int conv_delay[4]={100,200,400,800};
// valid temp. bit mask depending on the resolution
static flash unsigned bit_mask[4]={0xFFF8,0xFFFC,0xFFFE,0xFFFF};

unsigned char ds18b20_select(unsigned char *addr)
{
unsigned char i;
if (w1_init()==0) return 0;
if (addr)
   {
   w1_write(0x55);
   i=0;
   do
     w1_write(*(addr++));
   while (++i<8);
   }
else w1_write(0xcc);
return 1;
}

unsigned char ds18b20_read_spd(unsigned char *addr)
{
unsigned char i;
unsigned char *p;
if (ds18b20_select(addr)==0) return 0;
w1_write(0xbe);
i=0;
p=(char *) &__ds18b20_scratch_pad;
do
  *(p++)=w1_read();
while (++i<9);
return !w1_dow_crc8(&__ds18b20_scratch_pad,9);
}

float ds18b20_temperature(unsigned char *addr)
{
unsigned char resolution;
if (ds18b20_read_spd(addr)==0) return -9999;
resolution=(__ds18b20_scratch_pad.conf_register>>5) & 3;
if (ds18b20_select(addr)==0) return -9999;
w1_write(0x44);
delay_ms(conv_delay[resolution]);
if (ds18b20_read_spd(addr)==0) return -9999;
w1_init();
return (*((int *) &__ds18b20_scratch_pad.temp_lsb) & bit_mask[resolution])*0.0625;
}

unsigned char ds18b20_init(unsigned char *addr,signed char temp_low,signed char temp_high,
unsigned char resolution)
{
if (ds18b20_select(addr)==0) return 0;
resolution=(resolution<<5) | 0x1f;
w1_write(0x4e);
w1_write(temp_high);
w1_write(temp_low);
w1_write(resolution);
if (ds18b20_read_spd(addr)==0) return 0;
if ((__ds18b20_scratch_pad.temp_low!=temp_low) ||
   (__ds18b20_scratch_pad.temp_high!=temp_high) ||
   (__ds18b20_scratch_pad.conf_register!=resolution)) return 0;
if (ds18b20_select(addr)==0) return 0;
w1_write(0x48);
delay_ms(15);
return w1_init();
}