// 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 LM92-2.c -std=c99 -o LM92-2
// Run as user with R&W right on /dev/i2c-* (NOT ROOT!)
// vv@vvrpi ~ $ ./LM92-2 
// 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_TEMP 0                             // Temperature register (see data sheet)
#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;
	
        int16_t  data;
        int32_t  SMBUS_word;
        double   temperature;
        
        printf("Rapsberry Pi: I2C in C - Versione 0.64 - 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      
        printf("Reading from LM92 (bus: %s    Address: 0x%.2X    Register: %d)\n\n", device, I2C_ADDR,LM92_TEMP);
        if ( (SMBUS_word = i2c_smbus_read_word_data (fd , LM92_TEMP)) < 0) exit_on_error ("Error reading from SMBus");
        printf("Data read (as integer): 0x%X\n\n", SMBUS_word);

        // Convert to °C (see data sheet)
        data = ((SMBUS_word >> 8) | (SMBUS_word << 8)) & 0xFFFF;
        data = data >> 3;         
        temperature = LM92_RES * data;
        
        printf("Temperature: %2.1f °C\n\n", temperature);
        
        close(fd);

	return (0);
}