#include <stdlib.h>
#include <stdio.h> //to print error 

#include <unistd.h> //header file for standard I2c send and receive commands
#include <sys/ioctl.h> //setup I2c devices
#include <linux/i2c-dev.h> //definitions and structures 
#include <i2c/smbus.h> //smbus commands

#include "HTU21D_H.h"

//Declarations of functions
// Temperature:
int get_temp(int fd, double *temp){
	reset_sensor(fd);
	char buffer[3];
	__s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_TEMP, sizeof(buffer), buffer);
	if (res < 0){
		perror("Error -1: Failed to read from the device");
		return -1;
	}
	*temp = -46.85+175.72*(buffer[0]*256+buffer[1])/65536.0;
	return 0;
}

// Humidity 
//int get_hum(int fd, double *hum);
int get_hum(int fd, double *hum){
	reset_sensor(fd);
	char buffer[3];
	__s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_HUM, sizeof(buffer), buffer);
	if ( res < 0 ){
		perror("Error -3: Failed to read humidity ");
		return -1;
	}
	*hum = -6+125*(buffer[0]*256+buffer[1])/65536.0;
	return 0;
}

// Reset Sensor 
int reset_sensor(int fd){
	if(0 > ioctl(fd, I2C_SLAVE, HTU21D_ADDR)){
		perror("Error -2: Failed to reset");
		return -2;
	}
	i2c_smbus_write_byte(fd, HTU21D_RESET);
	return 0;
}