// Rapsberry Pi: I2C in C - Versione 0.61 - Luglio 2013
// Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/RaspberryPi/i2c_c.htm

// Compile:  gcc LM92.c -std=c99 -o LM92
// Run as user with R&W right on /dev/i2c-* (NOT ROOT!)
// vv@vvrpi ~ $ ./LM92 
// Using LM92 - I2C 

#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/i2c-dev.h>
#include <stdlib.h>

#define I2C_ADDR 0x4B				// Device adress

#define LM92_RES 0.0625                         // Resolution (see data sheet)

static const char *device = "/dev/i2c-1";	// I2C bus

static void exit_on_error (const char *s)	// Exit and print error code
{ 	perror(s);
  	abort();
} 

int main(int argc, char *argv[])
{
	int fd;
	
	uint8_t  buffer[2];
        int16_t  data;
        double   temperature;
        
        printf("Rapsberry Pi: I2C in C - Versione 0.61 - Luglio 2013\n");
        printf("Copyright (c) 2013, Vincenzo Villa (https://www.vincenzov.net)\n");
        printf("Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.\n");
        printf("Creative Commons | Attribution-Share Alike 3.0 Unported\n");
        printf("https://www.vincenzov.net/tutorial/elettronica-di-base/RaspberryPi/i2c-c.htm\n\n");                                       

       	// Open I2C device
       	if ((fd = open(device, O_RDWR)) < 0) exit_on_error ("Can't open I2C device");

	// Set I2C slave address
	if (ioctl(fd, I2C_SLAVE,I2C_ADDR) < 0) exit_on_error ("Can't talk to slave");
        
        // Read from LM92 (from Power-up default register)      
        printf("Reading from LM92 at address 0x%.2X on %s\n\n", I2C_ADDR, device);
        if (read(fd,buffer,2) != 2 ) exit_on_error ("Failed to read from the i2c bus");  
        printf("Data read from Power-up default register: 0x%.2X%.2X\n\n", buffer[0], buffer[1]);      
        
        data =  buffer[0];
        data = data << 8;
        
        data = data | buffer[1];
        data = data >> 3;
        temperature = LM92_RES * data;
        
        printf("Temperature: %2.1f °C\n\n", temperature);
        
        close(fd);

	return (0);
}