I've created a small I2C library to access the HYGROSENS HY321 module on the ARDUINO. I bought my sensor from REICHELT for about 12€.

You can find a usage sample here.

The library can be downloaded from here. Copy the library (*.c, *.cpp, *.txt) to your local libraries (taken from arduino.cc):

Open your Arduino sketchbook folder. If there is already a folder there called libraries, place the library folder in there. If not, create a folder called libraries in the sketchbook folder, and drop the library folder in there. Then re-start the Arduino programming environment, and you should see your new library in the Sketch > Import Library menu.

#ifndef _HYT321_H
#define _HYT321_H

class HYT321 {
      int rawTemp;
      int rawHum;
      int address;

      HYT321(int adr);
      uint8_t begin( void );
      uint8_t read( void );

      int getRawHumidity( void );
      int getRawTemperature( void ) ;
      double getHumidity( void ) ;
      double getTemperature( void );

extern HYT321 HYT;


You can access it via the class HYT321. The code sequence is pretty simple:

#include <Wire.h>
#include <HYT321.h>

HYT321 HYT = HYT321(0x28);

void setup() {
   // initialize I2C protocoll

   // initialize the sensor


void loop() {

   double h = HYT.getHumidity();
double t = HYT.getTemperature();

   for (;;);


2014 CW (Morse Telegraphy) was added to the German Nationwide Inventory of Intangible Cultural Heritage.