mikrokontrollersystemer-prosjekt/prosjekt.X/thermistor-temp.c

#include "themistor-temp.h"


void init_alarm_gpio(){
    PORTB.DIRSET = ALERT_PIN;    
}

float calculate_thermistor_temp(float thermistor_voltage){
    float R_thermistor;
    float V_1;
    float ln; 
    float T_thermistor;
    float V_thermistor;
    #define V_TOT 3.3
    // Calculate Voltage over thermistor
    V_thermistor = (V_TOT/1024)*thermistor_voltage;
    
    // Voltage accross R_1
    V_1 = V_TOT - V_thermistor; 
    
    // Calculate Thermistor resistanse
    R_thermistor = (V_thermistor)/ (V_1 / R_1);
    
    // Steinhart-Harts formula
    ln = log(R_thermistor/R_T0);
    T_thermistor = (1/ ((ln/B) + (1/T_0)));
    
    // Temperatur in celcius
    T_thermistor -= 273.15;
    
    return T_thermistor;
}

// returns error message if the messured thermistor temp is higher than
// Choosen max_temp
bool voltage_threshold_bool(float thermistor_temp, uint8_t max_temp){
    // Return true if temp is higher then max value
    return (thermistor_temp >= max_temp);
}

//print if the maximum threshold is exceeded. 
void alert_voltage_threshold_exceeded(bool voltage_threshold_bool){
    if (voltage_threshold_bool){
        printf("Error: maximum temperature exceeded");
        PORTB.OUTSET = ALERT_PIN; 
    }  else{
        PORTB.OUTCLR = ALERT_PIN; 
    }
}