updated thermistor equation

Author: mahir-mahota

Sensors/Core/Inc/lim.h

@@ -18,11 +18,12 @@
 //Steinhart-Hart constants
 #define MAX_ADC_COUNT           4095U
 #define ABSOLUTE_ZERO           273.15
-#define NOMINAL_TEMPERATURE     25U
+#define NOMINAL_TEMPERATURE     298.15
 #define NOMINAL_RESISTANCE      10000U
 #define B_COEFFICIENT           3950U
 
-#define VOLTAGE_SUPPLY          5U
+#define VOLTAGE_SUPPLY          5
+#define MAX_VOLTAGE             3.3
 #define R10K                    10000U
 
 

Sensors/Core/Src/lim.c

@@ -29,9 +29,11 @@ void get_lim_data(uint8_t lim_temps[NUM_LIMS]) {
 }
 
 uint8_t get_temp(uint16_t adc_value) {
-		uint32_t voltage_in = adc_value * (VOLTAGE_SUPPLY / MAX_ADC_COUNT);
-		uint32_t thermistor_resistance = voltage_in * R10K / (VOLTAGE_SUPPLY - voltage_in);
+		uint32_t voltage_in = adc_value * (MAX_VOLTAGE / MAX_ADC_COUNT);
+		uint32_t thermistor_resistance = (voltage_in * R10K) / (VOLTAGE_SUPPLY - voltage_in);
+
+		uint8_t temp_steinhart = -ABSOLUTE_ZERO + (NOMINAL_TEMPERATURE * B_COEFFICIENT)/(NOMINAL_TEMPERATURE
+				                 * log(thermistor_resistance / R10K) + B_COEFFICIENT);
 
-		uint8_t temp_steinhart = -ABSOLUTE_ZERO + (1.0/((1.0/ (NOMINAL_TEMPERATURE + ABSOLUTE_ZERO)) + (log(thermistor_resistance / NOMINAL_RESISTANCE) / B_COEFFICIENT)));
 		return temp_steinhart;
 }