// Rapsberry Pi: I2C con wiringPi - Versione 1.3 - Marzo 2018
// Copyright (c) 2013-2018, Vincenzo Villa
// Creative Commons | Attribuzione - Condividi allo stesso modo 4.0 Internazionale (CC BY-SA 4.0)
// Creative Commons | Attribution-Share Alike 4.0 Unported
// https://www.vincenzov.net/tutorial/RaspberryPi/i2c_wpi.htm

// pi@raspberrypi:~ $ gcc -Wall -o LM75A_thermostat LM75A_thermostat.c -lwiringPi
// pi@raspberrypi:~ $ ./LM75A_thermostat

// Write to LM75A TOS and THYST registers "thermostat mode"
// See LM75A data sheet for details

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <wiringPiI2C.h>

#define LM75A_ADDR 0x4F // LM75A I2C address
#define LM75A_CONF 1    // Configuration register
#define LM75A_TEMP 0    // Temperature register
#define LM75A_TOS 3     // Overtemperature shutdown threshold registe
#define LM75A_THYST 2   // Hysteresis register

#define HYSTERESIS 22.5   // Required hyseresis °C
// example: if T < 22.5, LED switch OFF
#define THRESOLD 25       // Required temperature shutdown threshold °C 
// example: if T > 25, LED switch ON

int main(int argc, char** argv) {
    int fd; // Standard Linux filehandle for I2C device
    int data; // Data as read from wiringPiI2CReadReg16() or as required from wiringPiI2CWriteReg16())
    int16_t raw16; // Word from I2C device
    double temperature, tos, thyst;
  
    setbuf(stdout, NULL); // NetBeans hack: disable buffering on stdout

    fd = wiringPiI2CSetup(LM75A_ADDR); // Initialises the I2C system
    // if (fd < 0) Error...

    data = wiringPiI2CReadReg16(fd, LM75A_TEMP); // Get 2 bytes from LM75A: actual temperature
    // if (data < 0) Error...
    raw16 = ((data << 8) & 0xFF00) | ((data >> 8) & 0xE0); // Adjust MSB and LSB
    temperature = (double) raw16 / 256; // Convert word from LM75A to degree Celsius
    printf("Temperature: %4.3f degree Celsius\n", temperature);

    // Write and read-back Overtemperature shutdown threshold
    raw16 = THRESOLD * 256;
    data = ((raw16 << 8) & 0x8000) | ((raw16 >> 8) & 0xFF); // Adjust MSB and LSB
    data = wiringPiI2CWriteReg16(fd, LM75A_TOS, data); // Write to LM75A address
    // if (data < 0) Error...

    data = wiringPiI2CReadReg16(fd, LM75A_TOS); // Get 2 bytes from LM75A (Overtemperature shutdown threshold))
    raw16 = ((data << 8) & 0xFF00) | ((data >> 8) & 0x80); // Adjust MSB and LSB
    tos = (double) raw16 / 256; // Convert word from LM75A to degree Celsius

    // Write and read-back Hysteresis
    raw16 = HYSTERESIS * 256;
    data = ((raw16 << 8) & 0x8000) | ((raw16 >> 8) & 0xFF); // Adjust MSB and LSB
    data = wiringPiI2CWriteReg16(fd, LM75A_THYST, data); // Write to LM75A address (Hysteresis)
    // if (data < 0) Error...

    data = wiringPiI2CReadReg16(fd, LM75A_THYST); // Get 2 bytes from LM75A (Hysteresis)
    // if (data < 0) Error...
    raw16 = ((data << 8) & 0xFF00) | ((data >> 8) & 0x80); // Adjust MSB and LSB
    thyst = (double) raw16 / 256; // Convert word from LM75A to degree Celsius
    
    printf("The LED becomes active when temperature exceeds %3.1f deg C, and leaves the active state when the temperature drops below %3.1f deg C\n\n", tos, thyst);

    return (EXIT_SUCCESS);
}