#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/ioctl.h>

#include <dev/iicbus/iic.h>

#define	I2C_DEV		"/dev/iic1"
#define	TMP102_ADDR	(0x48 << 1)

#define	TMP102_CONF_EM	(1 << 4)

uint16_t read_reg(int fd, uint8_t reg)
{
	uint8_t bytes[2];
	int error;
	struct iic_rdwr_data data;
	struct iic_msg msgs[2] = {
		{0, IIC_M_WR | IIC_M_NOSTOP, 1, &reg},
		{0, IIC_M_RD | IIC_M_NOSTART, 2, bytes},
	};

	msgs[0].slave = TMP102_ADDR;
	msgs[1].slave = TMP102_ADDR;

	data.nmsgs = 2;
	data.msgs = msgs;
	error = ioctl(fd, I2CRDWR, &data);
	if (error) {
		perror("ioctl(I2CRDWR)");
		return (0);
	}

	return ((bytes[0] << 8) | bytes[1]);
}

int reg_to_temp(uint16_t val, int extended)
{
	int sign, temp;
	int bits;

	if (extended) {
		bits = 13;
		val >>= 3;
	}
	else
		val >>= 4;

	if (val & (1 << (bits - 1))) {
		sign = -1;
		val = (1 << bits) - val;
	}
	else
		sign = 1;

	temp = val * 1000 / 16;

	return (temp*sign);
}

int main(int argc, char **argv)
{
	int fd;
	uint16_t conf, v;
	int em;

	fd = open(I2C_DEV, O_RDWR);
	if (fd < 0) {
		perror("open");
		return (1);
	}

	conf = read_reg(fd, 1);
	em = ((conf & TMP102_CONF_EM) != 0);

	printf("CFG = %04x\n", conf);
	v = read_reg(fd, 0);
	printf("TMP = %d mC (%02x)\n", reg_to_temp(v, em), v);
	v = read_reg(fd, 2);
	printf("TMP_LOW = %d mC (%02x)\n", reg_to_temp(v, em), v);
	v = read_reg(fd, 3);
	printf("TMP_HIGH = %d mC (%02x)\n", reg_to_temp(v, em), v);

	close(fd);

}