ntc.h

00001 /*
00002  * mbed library for NTC analog pin that translates an A:D input
00003  *     voltage to a temperature value.
00004  *
00005  *
00006  *     topology:  Vref -> SeriesRes -> A:D -> NTC -> GND
00007  *
00008 */
00009 
00010 #ifndef        MBED_NTC
00011 #define        MBED_NTC
00012 
00013     /** 
00014      * Private data structure for NTC data values.
00015      * 
00016     **/
00017     typedef struct {
00018         float vref ;         /*!< Referense voltage*/
00019         float ad_resolution ; /*!< A:D resolution*/
00020         int ntc_res ;        /*!< NTC resistance value at 25C*/
00021         int ntc_tol ;        /*!< NTC initial tolerance %*/
00022         int ntc_beta_0050 ;  /*!< NTC Beta, B0/50*/
00023         int ntc_beta_2550 ;  /*!< NTC Beta, B25/50*/
00024         int ntc_beta_2580 ;  /*!< NTC Beta, B25/80*/
00025         int ntc_beta_2585 ;  /*!< NTC Beta, B25/85*/
00026         int ntc_beta_25100 ; /*!< NTC Beta, B25/100*/
00027         int ntc_beta_other ; /*!< NTC Beta, other value vs temp*/
00028         int ntc_beta_tol ;   /*!< NTC Beta tolerance %*/
00029         int sres_res ;       /*!< Series resistor value*/
00030         int sres_tol ;       /*!< Series resistor tolerance %*/
00031         int sres_ppm ;       /*!< Series resistor tempco in ppm*/
00032     } NTC_TypeDef;
00033 
00034     /** 
00035      * Default values for data structure above
00036      * 
00037     **/
00038     const NTC_TypeDef ntc_std_paramtr = {
00039         // Vref
00040         3.0f,               // Vref
00041         16384.0f,           // A:D resolution
00042         // muRata NCP15XH103J03RC
00043         20000,              // NTC resistance
00044         3,                  // NTC initial tolerance
00045         0,                  // NTC B0/50, none
00046         3300,               // NTC B25/50
00047         3322,               // NTC B25/80
00048         3333,               // NTC B25/85
00049         3344,               // NTC B25/100
00050         0,                  // NTC other Beta value
00051         2,                  // NTC beta tolerance
00052         // 3.32k 1% 100ppm
00053         4750,               // Series resistor value
00054         1,                  // Series resistor tolerance
00055         200                 // Series Resistor tempco ppm
00056     };
00057 
00058     /** NTC temperature A:D conversion
00059      *
00060      * @code
00061      *  #include "mbed.h"
00062      *  #include "ntc.h" 
00063      *
00064      *  #define NTC_VREF        3.3f
00065      *  #define NTC_AD_RESOL    65536.0f
00066      *
00067      *  // Connections:
00068      *
00069      *  //      3.3V (or other Vref)
00070      *  //     --+--
00071      *  //       |
00072      *  //      -+-
00073      *  //     |   |
00074      *  //     |   |
00075      *  //     |   | Series
00076      *  //     |   | Resistor
00077      *  //     |   |
00078      *  //      -+-
00079      *  //       |
00080      *  //       +---> To A:D
00081      *  //       |
00082      *  //      -+-
00083      *  //     |   |
00084      *  //     |   |
00085      *  //     |   | NTC
00086      *  //     |   | 
00087      *  //     |   |
00088      *  //      -+-
00089      *  //       |
00090      *  //     --+--
00091      *  //      ---  Ground
00092      *  //       -
00093      *
00094      *  
00095      *  const NTC_TypeDef ntc_my_paramtr = {
00096      *    // Vref
00097      *    NTC_VREF,           // Vref
00098      *    NTC_AD_RESOL,       // A:D 16-bit resolution
00099      *    // muRata NCP15XH103J03RC
00100      *    10000,              // NTC resistance
00101      *    5,                  // NTC initial tolerance
00102      *    0,                  // NTC B0/50 (none)
00103      *    3380,               // NTC B25/50
00104      *    3428,               // NTC B25/80
00105      *    3434,               // NTC B25/85
00106      *    3355,               // NTC B25/100
00107      *    0,                  // NTC other beta (none)
00108      *    1,                  // NTC beta tolerance
00109      *    // 3.32k 1% 100ppm
00110      *    3320,               // Series resistor value
00111      *    1,                  // Series resistor tolerance
00112      *    100                 // Series Resistor tempco ppm
00113      *  };    
00114      *
00115      *  NTC ntc(A1, &ntc_my_paramtr);                   //initialize NTC temperature A:D
00116      * 
00117      *  main() {
00118      *      printf("\r\n\r\n-------------------------------------------\r\n");
00119      *      printf("NTC Res: %5d   B0/50: %4d   B25/50: %4d   B25/80: %4d   B25/85: %4d   B25/100: %4d   B_OTHER: %4d   SeriesR: %d\r\n", 
00120      *                  ntc.get_ntc_res(), ntc.get_ntc_beta(NTC::B0_50), ntc.get_ntc_beta(NTC::B25_50), ntc.get_ntc_beta(NTC::B25_80), ntc.get_ntc_beta(NTC::B25_85), 
00121      *                  ntc.get_ntc_beta(NTC::B25_100), ntc.get_ntc_beta(NTC::B_OTHER),  ntc.get_series_res());
00122      *      uint16_t ad = ntc.read_ad_reg();
00123      *      printf("NTC A:D Val: %5d   Volt A:D: %.6f   NTC-R_now: %7.1f    Temp: %+.2f\r\n", ad, 
00124      *              NTC_VREF / NTC_AD_RESOL * (float)ad, ntc.get_ntc_res_viaAD(ad), ntc.get_ntc_temp(NTC::B25_85, ad));
00125      *
00126      *      while(1) {
00127      *          printf("Temp: %+.2f\r\n", ntc.get_ntc_temp(NTC::B25_85));
00128      *          wait(2.0);
00129      *      }
00130      *          
00131      *  }         
00132      * @endcode
00133      */
00134  
00135 class NTC
00136 {
00137 public:
00138     /** 
00139      * NTC Beta curves to choose from for Temperature calculations
00140      * 
00141     **/
00142     enum ntcBetaCurve {
00143         B0_50 ,   /*!<  use B0/50 curve */
00144         B25_50 ,  /*!<  use B25/50 curve */
00145         B25_80 ,  /*!<  use B25/80 curve */
00146         B25_85 ,  /*!<  use B25/85 curve */
00147         B25_100 , /*!<  use B25/100 curve */
00148         B_OTHER , /*!<  use other curve */
00149     };
00150 
00151     /** Configure gpio pin
00152       * @param A:D I/O pin
00153       * @param parameters for NTC (NTC_TypeDef)
00154       */
00155     NTC(PinName p_ana, const NTC_TypeDef *ntc_parameter);
00156     
00157     /** Configure gpio pin
00158       * @param A:D I/O pin
00159       * uses default parameters
00160       */
00161     NTC(PinName p_ana);
00162     
00163     /** Read A:D register value
00164       * @param none
00165       * @return A:D value from 0-65535
00166       */
00167     uint16_t read_ad_reg();
00168     
00169     /** Get the NTC resistance value
00170       * @param none
00171       * @return resistance of NTC at 25C
00172       */
00173     int get_ntc_res();
00174     
00175     /** Get the NTC beta value
00176       * @param ntcBetaCurve selection
00177       * @param B25_85 default value
00178       * @return beta curve value
00179       */
00180     int get_ntc_beta(int beta = B25_85 );
00181        
00182     /** Get the resistance value for the series resistor
00183       * @param none
00184       * @return resistance of series resistor
00185       */
00186     int get_series_res();
00187     
00188     /** calculate NTC resistance based on A:D reading
00189       * @param none
00190       * @param din optional read from read_ad_reg().
00191       * @param din -> if missing or 0, read_ad_reg() value is used for calculation
00192       * @param din -> if != 0, then value of din is used for calculation
00193       * @return resistance of NTC
00194       */
00195     float get_ntc_res_viaAD(uint16_t din = 0);
00196       
00197     /** calculate NTC temperaure
00198       * @param curve Beta curve to use. See ntcBetaCurve {};
00199       * @param din optional read from read_ad_reg()
00200       * @param din -> if missing or 0, read_ad_reg() value is used for calculation
00201       * @param din -> if != 0, then value of din is used for calculation
00202       * @return temperature of NTC
00203       * @return -100 if NTC Beta selected = 0
00204       */
00205     float get_ntc_temp(int curve, uint16_t din = 0);
00206     
00207 protected:
00208     AnalogIn  _ana;
00209 
00210 private:
00211     NTC_TypeDef ntc_set_data;
00212     uint16_t rawdata;
00213 
00214 };
00215 
00216 #endif  //  MBED_NTC