htu21d.h

00001 /**
00002 HTU21D / HPP828E031 driver for mbed.
00003 - Includes RTOS hooks if RTOS is detected during compile.
00004 Author: Kevin Braun
00005  **/
00006 
00007 #ifndef HTU21D_H
00008 #define HTU21D_H
00009 
00010 #include "mbed.h"
00011 
00012 #if(defined(TARGET_KL25Z) )//|| defined(TARGET_K64F))
00013 
00014     #define HTU21Di2cLOWLEVEL   1           //if the use of low-level I2C routines is needed
00015     #warning "HTU21D using low level I2C routines"
00016     
00017 #endif
00018 
00019 //Defines for HTU21D
00020 #define HTU21Di2cWRITE      0x80
00021 #define HTU21Di2cREAD       0x81
00022 
00023 #define HTU21DWRITEUSER     0xE6
00024 #define HTU21DREADUSER      0xE7
00025 #define HTU21DtempNOHOLD    0xF3
00026 #define HTU21DhumNOHOLD     0xF5
00027 #define HTU21DRESET         0xFE
00028 
00029 #define HTU21SNAC1          0xFC
00030 #define HTU21SNAC2          0xC9
00031 #define HTU21SNB1           0xFA
00032 #define HTU21SNB2           0x0F
00033 
00034 #define HTU21DHEATER        0x04
00035 
00036 
00037     /**
00038     * measurement specialties / Honeywell HTU21D digital humidity and temperature sensor.
00039     * - Web site: http://www.meas-spec.com  
00040     * - Part Number: HPP828E031
00041     * - HTU21D = +-3% rh error at 55%
00042     * - HTU20D = +-5% rh error at 55%
00043     * - Main code generated from datasheet dated October 2013
00044     * - Serial number code generated from App Note "HTU2X Serial Number Reading", dated Februrary 2014
00045     * - No checksum checking is performed in this code
00046     *
00047     * @code
00048     * //Tested on FRDM-K64F
00049     *
00050     * #include "mbed.h"
00051     * #include "htu21d.h"
00052     *
00053     * #define SDA     PTE25 
00054     * #define SCL     PTE24
00055     *
00056     * Serial pc(USBTX, USBRX);                  //local terminal
00057     * htu21d htu(SDA, SCL);                     //Temp Hum || sda, scl
00058     *
00059     * float H21Temp = 0.0;                      //Temperture from HTU21D
00060     * float H21Hum = 0.0;                       //Humidity from HTU21D
00061     * float H21Dew = 0.0;                       //Dew Point from HTU21D
00062     *
00063     * //Note: If RTOS is used, Mutex for I2C must be initialized
00064     * #ifdef RTOS_H
00065     * Mutex MutexI2cWait;
00066     * #endif
00067     *
00068     * int main() {
00069     *     pc.baud(230400);                        //local terminal baud
00070     *     pc.printf("\r\n\r\nK64F_HTU21D basic operation\r\n"); 
00071     * 
00072     *     //initialize the HTU21D
00073     *     int htu21 = htu.softReset();
00074     *     if(htu21 == 0) {
00075     *         pc.printf(" - HTU21D broken...\r\n");
00076     *     } else {
00077     *         uint8_t HTU21DuserReg = htu.getUserReg();
00078     *         pc.printf("HTU21D UserReg: 0x%02x   SN: 0x%04x %08x %04x\r\n", 
00079     *                   HTU21DuserReg, htu.HTU21sn.HTU21D_sna, htu.HTU21sn.HTU21D_snb, htu.HTU21sn.HTU21D_snc);
00080     *     }
00081     * 
00082     *     while(true) {
00083     *         //get humidity, temperature and dew point from HTU21D
00084     *         if(htu21 == 1) {    //if HTU21D didn't initialize, don't access HTU21D anymore
00085     *             H21Hum = htu.getHum();
00086     *             if((double)H21Hum == 255.0) pc.printf("\r\n*** HTU21D Hum error!!\r\n");
00087     *             H21Temp = htu.getTemp();
00088     *             if((double)H21Temp == 255.0) pc.printf("\r\n*** HTU21D Temp error!!\r\n");
00089     *             H21Dew = htu.getDewPtFast();
00090     *         }
00091     *         pc.printf("Temp: %7.2f C %7.2f F   Hum: %4.1f %%   DewPt: %7.2f C\r\n", H21Temp, H21Hum, H21Dew);
00092     *         wait(1.0);
00093     *     }
00094     * }
00095     * @endcode
00096     **/
00097 class htu21d {
00098 
00099 public:
00100     /**
00101      * Constructor
00102      * - Fixed at I2C address 0x80
00103      * - I2C speed set to 400000
00104      *
00105      * @param PinName sda and scl, mbed I2C interface pins
00106      */
00107     htu21d(I2C i2c);
00108     /**
00109      * Constructor
00110      * - Fixed at I2C address 0x80
00111      * - I2C speed set by user
00112      *
00113      * @param PinName sda and scl, mbed I2C interface pins 
00114      * @param int I2C frequency
00115      */
00116     /**
00117      * Destructor
00118      *
00119      * @param --none--
00120      */
00121     ~htu21d();
00122     /**
00123      * Reset the HTU21D chip
00124      * - Waits 15mS before exiting, allowing the chip reset to finish
00125      * - Executes getSNReg() which loads up HTU21D serial number structure
00126      * 
00127      * @param --none-- NOTE: run softReset() once at initialization time
00128      *
00129      * @return success / failure of HTU21D i2c access. 1 = ok, 0 = error
00130     */
00131     int softReset();
00132     /**
00133      * Get HTU21D user register
00134      * 
00135      * @param --none--
00136      *
00137      * @return 8 bit user register value
00138     */
00139     uint8_t getUserReg();
00140     /**
00141      * Turn ON the heater on the HTU21D
00142      * 
00143      * @param --none--
00144      *
00145      * @return success / failure of HTU21D i2c access. 1 = ok, 0 = error
00146     */
00147     int heaterOn();
00148     /**
00149      * Turn OFF the heater on the HTU21D
00150      * 
00151      * @param --none--
00152      *
00153      * @return success / failure of HTU21D i2c access. 1 = ok, 0 = error
00154     */
00155     int heaterOff();
00156     /**
00157      * Get heater on/off status of the HTU21D
00158      * 
00159      * @param --none--
00160      *
00161      * @return 0x04 = on, 0 = off
00162     */
00163     uint8_t getHeater();
00164     /**
00165      * Get HTU21D Temperature
00166      * 
00167      * @param --none--
00168      *
00169      * @return float of Temperature in degrees C.  255.0 if error
00170     */
00171     float getTemp();
00172     /**
00173      * Get HTU21D Humidity
00174      * 
00175      * @param --none--
00176      *
00177      * @return float of Humidity in percentage.  255.0 if error
00178     */
00179     float getHum();
00180     /**
00181      * Calculate the Dew Point
00182      * 
00183      * @param --none-- NOTE: You MUST run getTemp() and getHum() first!!
00184      *
00185      * @return float of Dew Point
00186     */
00187     float getDewPt();
00188     /**
00189      * Calculate the Dew Point fast
00190      * - 5x faster than getDewPt()
00191      * - slightly less accurate than getDewPt()
00192      * 
00193      * @param --none-- NOTE: You MUST run getTemp() and getHum() first!!
00194      *
00195      * @return float of Dew Point
00196     */
00197     float getDewPtFast();
00198     /**
00199      * Structure to access HTU21D's serial number 
00200      * - HTU21D_sna is the hi  16 bit word of the s/n, always is 0x4854
00201      * - HTU21D_snb is the mid 32 bit word of the s/n, 0x00--------
00202      * - HTU21D_snc is the low 16 bit word of the s/n, 0x32--
00203      * - The complete 64 bit s/n value is: 0x48 54 00 -- -- -- 32 --
00204      * - The numbers shown are fixed fields
00205      * - The '-' numbers are variable
00206      * - For reference, the CRC values for the s/n are included
00207     */    
00208     struct HTU21snStruct {
00209         uint16_t HTU21D_sna;            /**< Highest order 16 bit word of SN
00210                                             - Value always = 0x4854
00211                                             */
00212         uint32_t HTU21D_snb;            /**< Middle order 32 bit word of SN
00213                                             - Value = 0x00--------
00214                                             - Highest byte always = 0x00
00215                                             - Lower 3 bytes are variable
00216                                             */
00217         uint16_t HTU21D_snc;            /**< Lowest order 16 bit word of SN
00218                                             - Value = 0x32--
00219                                             - Highest byte always = 0x32
00220                                             - Lowest byte is variable
00221                                             */
00222         uint8_t HTU21D_crca;            /**< Single byte checksum from HTU21D_sna
00223                                             */  
00224         uint32_t HTU21D_crcb;           /**< Four byte checksum from HTU21D_snb
00225                                             */
00226         uint8_t HTU21D_crcc;            /**< Single byte checksum from HTU21D_snc
00227                                             */
00228         HTU21snStruct() {
00229             HTU21D_sna = 0;
00230             HTU21D_snb = 0;
00231             HTU21D_snc = 0;
00232             HTU21D_crca = 0;
00233             HTU21D_crcb = 0;
00234             HTU21D_crcc = 0;
00235         }
00236     } HTU21sn;
00237 
00238 private:
00239     I2C _i2c;
00240     /**
00241      * I2C access for getting raw Temperature and Humidity data
00242      * 
00243      * @param 8 bit HTU21D register to get data from. Must use non-blocking regs
00244      *
00245      * @return 16 bit raw i2c data, ANDed to 14 bits 0xFFFC. 0000 if error
00246     */
00247     uint16_t getData(uint8_t reg);
00248     /**
00249      * Get the HTU21D's serial number. 
00250      * - Number returned is 0x4854 00-- ---- 32--
00251      * - The numbers shown are fixed fields
00252      * - The '-' numbers are variable
00253      * 
00254      * @param --none--
00255      *
00256      * @return --none--
00257     */
00258 #if not defined HTU21Di2cLOWLEVEL
00259 char htuBuffer[8];
00260 #endif
00261     void getSNReg();
00262     double theTempIs;
00263     double theHumIs;
00264 };
00265 
00266 #endif