SMTC502AT.cpp

00001 #include "mbed.h"
00002 #include "SMTC502AT.h"
00003 
00004 SMTC502AT::SMTC502AT(AnalogIn *ain, float R0, float R1, float B, float T0) 
00005 {
00006     _ain = ain ;
00007     _r0 = R0 ;
00008     _r1 = R1 ;
00009     _b  = B ;
00010     _t0 = T0 ;
00011 }
00012 
00013 SMTC502AT::~SMTC502AT(void)
00014 {
00015     if (_ain) {
00016         delete _ain ;
00017     }
00018 }
00019 
00020 /**
00021  * getTemp returns the temperature
00022  * operational temperature is -50C to +105C
00023  */
00024 float SMTC502AT::getTemp(void)
00025 {
00026     float result = 0.0 ;
00027     float f, raw, rr1, t ;
00028     if (_ain) {
00029         f = _ain->read() ;
00030 #if 0
00031         if (f < 0.087) { /* +105C */
00032             printf("Temp is Too high or the sensor is absent\n") ;
00033             f = 0.087 ;
00034         }
00035         if (f > 0.978) { /* -50C */
00036             printf("Temp is Too low or the sensor encountered a problem\n") ;
00037             f = 0.978 ;
00038         }
00039 #endif
00040         raw = f * 3.3 ;
00041         rr1 = _r1 * raw / (3.3 - raw) ;
00042         t = 1.0 / (log(rr1 / _r0) / _b + (1/_t0)) ;
00043         result = t - 273.15 ;
00044     }
00045     return( result ) ;
00046 }
00047