#include <math.h>
#include <stdint.h>

#define USE_CALC

#ifdef USE_CALC
#define NTC_A1 0.003354016f // see NTC RT csv from Vishay
#define NTC_B1 0.000300131f
#define NTC_C1 5.08516E-06f
#define NTC_D1 2.18765E-07f
  
#define VREF 3000.0f // 3V
#define TEMP_CONV 1000.0f // 65.535°C max; maybe 100 for better safety against overflow
#define CELSIUS_TO_KELVIN 273.15f
#define CELSIUS_TO_KELVIN_SCALED CELSIUS_TO_KELVIN * TEMP_CONV

// More efficient (?) calc using:
// R_T = R_Pullup / (V_REF / ADC - 1)
// With R_T/R_0 and R_0 = R_T@25C
// R_T/R_0 = 1 / V_REF / ADC - 1

[[gnu::optimize("fast-math")]]
static inline uint16_t ntc_mv_to_celsius(int16_t adc) {
  float log_ohms = logf(1 / ((VREF / adc) - 1));
  return (uint16_t) (TEMP_CONV / (NTC_A1 + NTC_B1 * log_ohms + NTC_C1 * log_ohms * log_ohms + NTC_D1 * log_ohms * log_ohms * log_ohms) - CELSIUS_TO_KELVIN_SCALED);
}
#else
// Lookup Table coming soon; not really needed but fun?
#endif