HDC1080: Problem getting a temperature reading.

I have the HDC1080 temperature and humidity sensor connected to a raspberry pi 3 via 3.3v, GND, SDA and SCL. I am trying to get a temperature reading using C and the wiringPi library. I keep reading '-1' from the 0x00 register.

This is my code:

#include <stdio.h>
    #include <wiringPi.h>
    #include <wiringPiI2C.h>

    int main()
    { 
      int fd, temp;
      unsigned int a = 15;

      delay(a);
      fd = wiringPiI2Csetup(0x40);   /*intializing i2c system*/
      delay(a);
     
      wiringPiI2CWrite(fd, 0x80);   /* sending slave byte for writing*/
      delay(a);
      
      wiringPiI2CWriteReg16(fd, 0x02, 0x00);  /*configuring measurement*/
      delay(a);
      
      wiringPiI2CWrite(fd, 0x80);
      delay(a);
      wiringPiI2CWrite(fd, 0x00);  /*triggering measurement*/
      delay(a);   /* waiting for measurement*/

     
      wiringPiI2CWrite(fd, 0x81);   /*sending slave byte for reading */
      delay(a);
      
      temp = wiringPiI2CReadReg16(fd,0x00);   /*reading temperature*/
      delay(a);
      temp = (((temp)/(2^16))*165)-40;   /*converting reading to degrees celsius*/
      printf("%d", temp);
    }