#include <stdio.h>
#include <unistd.h>
#include <onewire.h>
#include <ds18s20.h>

void ds18s20_convert(const struct owaddr *addr) {
	int power, status;
	
	ow_matchrom(addr);
	ow_writecommand(DS18S20_POWER);
	power = ow_readbit();
	
	ow_matchrom(addr);
	
	if (power == 0) {
		// Parasite power
		ow_spu(1);
		ow_writecommand(DS18S20_CONVERT);
		usleep(800000);
		ow_spu(0);
	} else {
		// External power
		ow_writecommand(DS18S20_CONVERT);
		
		do {
			usleep(100000);
			status = ow_readbit();
		} while (status != 1);
	}
}

/* Public functions */

void ds18s20_readsp(const struct owaddr *addr, unsigned char *buf) {
	// Read 9-byte stratchpad
	
	ow_matchrom(addr);
	ow_writecommand(DS18S20_READSP);
	ow_readbytes(buf, 9);
}

float ds18s20_temperature(const struct owaddr *addr) {
	unsigned char buf[9];
	
	ds18s20_convert(addr);
	ds18s20_readsp(addr, buf);
	
	if (ow_crc(buf, 9) != 0) {
		// Try again once
		ds18s20_readsp(addr, buf);
		
		if (ow_crc(buf, 9) != 0) {
			fprintf(stderr, "ds18s20 stratchpad CRC failed\n");
			return 85.;
		}
	}
	
	int temp_read, count_remain, count_per_c;
	float result;
	
	temp_read = buf[0] >> 1;
	if (buf[1])
		temp_read = - temp_read;
	
	count_remain = buf[6];
	count_per_c = buf[7];
	
	result = temp_read - 0.25;
	result += ((float) count_per_c - count_remain) / count_per_c;
	
	return result;
}