Basic class for reading thermistor values on a Spark Core

Spark-Thermistor.pde

#include <math.h>

class Thermistor {
    private:
        int _pin;
        int _resistor;
        int _temp_raw;
        float _temp_k;
        float _temp_c;
        float _temp_f;
    
    public:
        Thermistor(int pin, int resistor);
        void begin(void);
        float getTemp(void);
        float getTempF(void);
        float getTempC(void);
        float getTempK(void);
        int getTempRaw(void);
};


Thermistor::Thermistor(int pin, int resistor) {
    _pin = pin;
    _resistor = resistor;
}


void Thermistor::begin(void) {
    pinMode(_pin, INPUT);
}


int Thermistor::getTempRaw(void) {
    delay(1);
    return analogRead(_pin);
}


float Thermistor::getTempK() {
    getTempRaw();
    
    _temp_k = log(((40960000/_temp_raw) - _resistor));
    _temp_k = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * _temp_k * _temp_k ))* _temp_k);
    
    return _temp_k;
}


float Thermistor::getTempC() {
    getTempK();
    _temp_c = _temp_k - 273.15;
    
    return _temp_c;
}


float Thermistor::getTempF() {
    getTempC();
    _temp_f = (_temp_c * 9.0)/ 5.0 + 32.0;
    
    return _temp_f;
}


float Thermistor::getTemp() {
    return getTempC();
}


#define THERMPIN A0     // Spark Core analog input pin
#define THERMRES 10000  // Value of voltage divider resistor

Thermistor Thermistor(THERMPIN, THERMRES);

float t;
char str_t[7];


void setup() {
    Thermistor.begin();
    
    Spark.variable("t", &str_t, STRING);
}

void loop() {
    t = Thermistor.getTempF();
    
    sprintf(str_t, "%.2f", t);
}