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#include "project.h"
#define DS1820_READ_SCRATCHPAD 0xbe
#define DS1820_CONVERT_T 0x44
#define TIMEOUT 150
static unsigned extract_leu16 (uint8_t *d)
{
uint32_t u;
u = (uint32_t) d[0] | (((uint32_t) d[1]) << 8);
return u;
}
static int extract_les16 (uint8_t *d)
{
uint32_t u;
u = extract_leu16 (d);
if (u & 0x8000) u |= 0xffff0000;
return (int) u;
}
static int
ds1820_read_sp (const Onewire_addr *a, unsigned page, uint8_t *buf, unsigned len)
{
if (onewire_reset_and_select (a))
return ~0U;
onewire_write_byte (DS1820_READ_SCRATCHPAD);
onewire_read_bytes (buf, len);
if ((len == 9) && onewire_check_crc (buf, 8, buf[8]))
return ~0U;
return 0;
}
static int ds1820_convert_t (const Onewire_addr *a)
{
if (onewire_reset_and_select (a))
return ~0U;
onewire_write_byte (DS1820_CONVERT_T);
if (onewire_wait_complete (TIMEOUT))
return ~0U;
return 0;
}
int
ds1820_read (const Onewire_addr *a, int *temp)
{
uint8_t buf[9];
int t;
if (ds1820_read_sp (a, 0, buf, 9))
return 1;
if (ds1820_convert_t (a))
return 1;
if (ds1820_read_sp (a, 0, buf, 9))
return 1;
t = extract_les16 (&buf[0]);
t <<= 4 ;
if (temp)
*temp = t;
return 0;
}
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