File content as of revision 0:91e3e396bc6e:

/**
 * SHT21 - Temperature and Humidity Sensor by Sensiron
 *
 *  This is a driver to connect to the sensor using an mbed device through an I2C interface
 *
 * Author: Graeme Coapes - Newcastle University
 * Email: graeme.coapes@ncl.ac.uk
 *
 * Date:   28/11/2012
 * 
 */

#include "mbed.h"


#ifndef SHT21_ncleee
#define SHT21_ncleee

    /*
     * Constants used in communication
     *
     * Refer to datasheet for full explanation
     */ 
     
    //Sensor I2C address
    #define SHT_I2C_ADDR        0x80
    
    //Commands...
    //Trigger Temp with hold master
    #define SHT_TRIG_TEMP_HOLD  0xE3
    //Trigger RH with hold master
    #define SHT_TRIG_RH_HOLD    0xE5
    //Trigger Temp with no hold master
    #define SHT_TRIG_TEMP       0xF3
    //Trigger RH with no hold master
    #define SHT_TRIG_RH         0xF5
    //Write to user register
    #define SHT_WRITE_REG       0xE6
    //Read from user register
    #define SHT_READ_REG        0xE7
    //Soft reset the sensor
    #define SHT_SOFT_RESET      0xFE
    
    //User Register information
    
    //Data precision settings
    //RH 12 T 14 - default
    #define SHT_PREC_1214       0x00
    //RH 8  T 10 
    #define SHT_PREC_0812       0x01
    //RH 10 T 13
    #define SHT_PREC_1013       0x80
    //RH 11 T 11
    #define SHT_PREC_1111       0x81

    //Battery status
    #define SHT_BATTERY_STAT    0x40
    //Enable on chip heater
    #define SHT_HEATER          0x04
    //Disable OTP reload
    #define SHT_DISABLE_OTP     0x02
    
    
    //Fail conditions on the I2C bus
    #define SHT_FAIL            1
    #define SHT_SUCCESS         0
    
    //Author fail conditions
    //1, 2, 3 can be used because these are status bits
    //in the received measurement value
    #define SHT_GOOD            0xFFFC
    #define SHT_TRIG_FAIL       1
    #define SHT_READ_FAIL       2
    
    
    class SHT21
    {
        private:
            I2C *_i2c;
            int triggerTemp();  
            int requestTemp();
            unsigned short temperature;
            int triggerRH();
            int requestRH();
            unsigned short humidity;
            int wr(int cmd);
            
        public:
        
            /** Constructor - create a connection to a SHT21 temperature and humidity sensor
             * through an I2C interface
             *
             * @param *i2c a pointer to the i2c interface that is used for communication
             */             
            SHT21(I2C *i2c);
            int readTemp();
            int readHumidity();
            int reset();
            int setPrecision(char precision);
    
    };
    
    
#endif