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lm74.c
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lm74.c
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#include <stdlib.h>
#include "lm74.h"
#include "lm74conf.h"
#include "spi.h"
#define TEMPERATURE_START 3
#define TEMPERATURE_DECIMALS (TEMPERATURE_POINT - TEMPERATURE_START)
void lm74Init(void) {
spiInit();
read_temperature();
}
u08 format_temperature (char* buf, short temperature)
{
int i = 0;
temperature >>= TEMPERATURE_START;
// Handle negative values.
if (temperature & 0x8000) {
buf[i] = '-';
i++;
temperature = -temperature;
}
// Add integral part.
itoa(temperature>>TEMPERATURE_DECIMALS, &buf[i], 10);
for(;buf[i] != 0; i++);
buf[i] = '.';
i++;
// i += sprintf(&buf[i], "%d.", temperature >> TEMPERATURE_DECIMALS);
temperature &= ~(~0 << TEMPERATURE_DECIMALS);
if (!temperature) {
buf[i] = '0';
i++;
} else {
// Add fractional part.
while (temperature) {
buf[i] = '0' + ((temperature*10) >> TEMPERATURE_DECIMALS);
i++;
temperature = (temperature*10) & ~(~0 << TEMPERATURE_DECIMALS);
}
}
buf[i] = '\0';
i++;
return i;
}
short read_temperature(void) {
u16 result;
cbi(LM74_CS_PORT,LM74_CS_PIN);
result = spiTransferWord(0);
sbi(LM74_CS_PORT,LM74_CS_PIN);
return (u16)result;
}