//gcc -o lm75_test lm75_test.c
//
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

#include <linux/i2c-dev.h>
#include <fcntl.h>
#include <sys/ioctl.h>


int main(int argc, char **argv)
{
	int rtc;
	char *i2cFileName = "/dev/i2c-3";
	// char *i2cFileName = "/sys/class/i2c-dev/i2c-3";
	int rtcAddress = 0x90 >> 1;
	unsigned char buf[16];
 
	printf("***** start i2c test program *****\n");
	printf("Initializing RTC unit... Please wait\n");
	usleep(5000);
 
	if ((rtc = open(i2cFileName, O_RDWR)) < 0)
	{
		printf("Faild to open i2c port\n");
		exit(1);
	}

	if (ioctl(rtc, I2C_SLAVE, rtcAddress) < 0)
	{
		printf("Unable to get bus access to talk to slave\n");
		exit(1);
	}

	buf[0] = 0;
	if ((write(rtc, buf, 1)) != 1) {
		printf("Error writing to i2c slave\n");
		exit(1);
	}

	if (read(rtc, buf, 2) != 2)
	{
		printf("Uneble to read\n");
		exit(1);
	}

	printf("%x\n", buf[0]);
	printf("%x\n", buf[1] & 0x80);

	return 0;
}