SHT21_ncleee.h

00001 /* Copyright (c) 2012 Graeme Coapes, Newcastle University, MIT License
00002  *
00003  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
00004  * and associated documentation files (the "Software"), to deal in the Software without restriction, 
00005  * including without limitation the rights to use, copy, modify, merge, publish, distribute, 
00006  * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 
00007  * furnished to do so, subject to the following conditions:
00008  *
00009  * The above copyright notice and this permission notice shall be included in all copies or 
00010  * substantial portions of the Software.
00011  *
00012  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
00013  * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
00014  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
00015  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
00016  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00017  */
00018 
00019 
00020 #include "mbed.h"
00021 
00022 
00023 #ifndef SHT21_ncleee
00024 #define SHT21_ncleee
00025 
00026     /*
00027      * Constants used in communication
00028      *
00029      * Refer to datasheet for full explanation
00030      */ 
00031      
00032     //Sensor I2C address
00033     #define SHT_I2C_ADDR        0x80
00034     
00035     //Commands...
00036     //Trigger Temp with hold master
00037     #define SHT_TRIG_TEMP_HOLD  0xE3
00038     //Trigger RH with hold master
00039     #define SHT_TRIG_RH_HOLD    0xE5
00040     //Trigger Temp with no hold master
00041     #define SHT_TRIG_TEMP       0xF3
00042     //Trigger RH with no hold master
00043     #define SHT_TRIG_RH         0xF5
00044     //Write to user register
00045     #define SHT_WRITE_REG       0xE6
00046     //Read from user register
00047     #define SHT_READ_REG        0xE7
00048     //Soft reset the sensor
00049     #define SHT_SOFT_RESET      0xFE
00050     
00051     //User Register information
00052     
00053     //Data precision settings
00054     //RH 12 T 14 - default
00055     #define SHT_PREC_1214       0x00
00056     //RH 8  T 10 
00057     #define SHT_PREC_0812       0x01
00058     //RH 10 T 13
00059     #define SHT_PREC_1013       0x80
00060     //RH 11 T 11
00061     #define SHT_PREC_1111       0x81
00062 
00063     //Battery status
00064     #define SHT_BATTERY_STAT    0x40
00065     //Enable on chip heater
00066     #define SHT_HEATER          0x04
00067     //Disable OTP reload
00068     #define SHT_DISABLE_OTP     0x02
00069     
00070     
00071     //Fail conditions on the I2C bus
00072     #define SHT_FAIL            1
00073     #define SHT_SUCCESS         0
00074     
00075     //Author fail conditions
00076     //1, 2, 3 can be used because these are status bits
00077     //in the received measurement value
00078     #define SHT_GOOD            0xFFFC
00079     #define SHT_TRIG_FAIL       1
00080     #define SHT_READ_FAIL       2
00081     
00082     /** SHT21 Connection class, utilizing a I2C interface
00083      *  
00084      * Example:
00085      * @code
00086      *   #include "mbed.h"
00087      *   #include "SHT21_ncleee.h"
00088      *   
00089      *   
00090      *   DigitalOut myled(LED1);
00091      *   Serial pc(USBTX, USBRX);
00092      *   I2C i2c(p28,p27);
00093      *   SHT21 sht(&i2c);
00094      *   
00095      *   int main() 
00096      *   {
00097      *   
00098      *       pc.printf("Hello World...\n\tTesting temperature Sensor\n");
00099      *       
00100      *       int temperature = sht.readTemp();
00101      *   
00102      *       pc.printf("Temperature is: %d \n", temperature);
00103      *       
00104      *       pc.printf("Experiment complete...\n");
00105      *   
00106      *   }
00107      *        
00108      * @endcode
00109      *
00110      *
00111      */
00112     class SHT21
00113     {
00114         private:
00115             I2C *_i2c;
00116 //            Serial *_pc;
00117             int triggerTemp();  
00118             int requestTemp();
00119             unsigned short temperature;
00120             int triggerRH();
00121             int requestRH();
00122             unsigned short humidity;
00123             int wr(int cmd);
00124             
00125         public:
00126         
00127             /** Constructor - create a connection to a SHT21 temperature and humidity sensor
00128              * through an I2C interface
00129              *
00130              * @param *i2c a pointer to the i2c interface that is used for communication
00131              */             
00132             SHT21(I2C *i2c);
00133             
00134             /** Read the temperature value from the sensor \n
00135              *
00136              * Involves triggering the measuring unit then
00137              * waiting for 100ms for the measuring to complete 
00138              * before reading the temperature             
00139              * 
00140              * @param returns a value representing the temperature in degrees centigrade
00141              */ 
00142             float readTemp();
00143             
00144             /** Read the humidity value from the sensor \n
00145              *
00146              * Involves triggering the measuring unit then
00147              * waiting for 100ms for the measuring to complete 
00148              * before reading the humidity             
00149              * 
00150              * @param returns the percentage humidity
00151              */             
00152             float readHumidity();
00153             
00154             /**
00155              * Perform a soft-reset of the sensor unit.
00156              */
00157             int reset();
00158             
00159             /**
00160              * Set the precision of the measuring
00161              *
00162              *    //Data precision settings \n
00163              *    //RH 12 T 14 - default    \n
00164              *    #define SHT_PREC_1214       0x00 \n
00165              *    //RH 8  T 10 \n
00166              *    #define SHT_PREC_0812       0x01 \n
00167              *    //RH 10 T 13 \n
00168              *    #define SHT_PREC_1013       0x80 \n
00169              *    //RH 11 T 11 \n
00170              *    #define SHT_PREC_1111       0x81 \n
00171              *
00172              * @param precision - the precision, refer to above or datasheet.
00173              * 
00174              */ 
00175             int setPrecision(char precision);
00176     
00177     };
00178     
00179     
00180 #endif