Example C code can be found on SysConfg, with ASCStudio: HDC302x Example Code.

The following code provides an example of how to perform a temperature and humidity read on HDC302x with Arduino:

//HDC302x Sample Code v0.2
//Texas Instruments
//HG

#include <Wire.h>

// Data buffer to hold data from HDC Sensor
uint8_t HDC_DATA_BUFF[4];

//Humidity Variables
uint16_t HUM_MSB;
uint16_t HUM_DEC;
uint16_t HUM_OUTPUT;

//Temperature Variables
uint16_t TEMP_MSB;
uint16_t TEMP_DEC;
uint16_t TEMP_OUTPUT;

//Device and Address Configurations

#define DEVICE_ADDR 0x45       //

//Lowest noise, highest repeatability 
#define DEVICE_CONFIG_MSB 0x24 // 
#define DEVICE_CONFIG_LSB 0x00 //

void setup() {

  // put your setup code here, to run once:
  Wire.begin();
  Serial.begin(115200);
  Serial.println("HDC302x Sample Code");

}

void loop() {

  float humidity;
  float temp;

// send device command for highest repeatability 
  Wire.beginTransmission(DEVICE_ADDR);
  Wire.write(0x24); //send MSB of command
  Wire.write(0x00); //command LSB
  Wire.endTransmission();
  delay(25); //wait 25 ms before reading

  Wire.requestFrom(DEVICE_ADDR, 6); //request 6 bytes from HDC device
  Wire.readBytes(HDC_DATA_BUFF, 6); //move 6 bytes from HDC into a temporary buffer

  temp = getTemp(HDC_DATA_BUFF);
  Serial.print("Temp (C): ");
  Serial.println(temp);

  delay(1000);

  humidity = getHum(HDC_DATA_BUFF);
  Serial.print("Humidity (RH): ");
  Serial.print(humidity);
  Serial.println("%");

  delay(1000);

}

float getTemp(uint8_t humBuff[]) {

  float tempConv;
  float celsius;

  TEMP_MSB = humBuff[0] << 8 | humBuff[1]; //shift 8 bits off data in first array index to get MSB then OR with LSB
  tempConv = (float)(TEMP_MSB);
  celsius = ((tempConv / 65535) * 175) - 45; //calculate celcius using formula in data sheet
  
  return celsius; 

}

float getHum(uint8_t humBuff[]){

  float humConv;
  float humidity;

  HUM_MSB = (humBuff[3] << 8) | humBuff[4]; //shift 8 bits off data in first array index to get MSB then OR with LSB
  humConv = (float)(HUM_MSB);
  humidity = (humConv / 65535) * 100; //calculate celcius using formula in datasheet

  return humidity;

}