File content as of revision 1:73fc5aef174e:

/* Copyright (c) 2012 Graeme Coapes, Newcastle University, MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, 
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or 
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * 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
    
    /** SHT21 Connection class, utilizing a I2C interface
     *  
     * Example:
     * @code
     *   #include "mbed.h"
     *   #include "SHT21_ncleee.h"
     *   
     *   
     *   DigitalOut myled(LED1);
     *   Serial pc(USBTX, USBRX);
     *   I2C i2c(p28,p27);
     *   SHT21 sht(&i2c);
     *   
     *   int main() 
     *   {
     *   
     *       pc.printf("Hello World...\n\tTesting temperature Sensor\n");
     *       
     *       int temperature = sht.readTemp();
     *   
     *       pc.printf("Temperature is: %d \n", temperature);
     *       
     *       pc.printf("Experiment complete...\n");
     *   
        }
             
     * @endcode
     *
     *
     */
    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);
            
            /** Read the temperature value from the sensor \n
             *
             * Involves triggering the measuring unit then
             * waiting for 100ms for the measuring to complete 
             * before reading the temperature             
             * 
             * @param returns The temperature, a value of either 1,2 or 3 corresponds to an error
             */ 
            int readTemp();
            
            /** Read the humidity value from the sensor \n
             *
             * Involves triggering the measuring unit then
             * waiting for 100ms for the measuring to complete 
             * before reading the humidity             
             * 
             * @param returns The humidity, a value of either 1,2 or 3 corresponds to an error
             */             
            int readHumidity();
            
            /**
             * Perform a soft-reset of the sensor unit.
             */
            int reset();
            
            /**
             * Set the precision of the measuring
             *
             *    //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
             *
             * @param precision - the precision, refer to above or datasheet.
             * 
             */ 
            int setPrecision(char precision);
    
    };
    
    
#endif