Converts ADC value of the internal temperature sensor of STM32 microcontroller to degrees Celsius taking into account calibration.

stm32_internal_temperature_sensor.c

/**
 * @brief Converts ADC_CHANNEL_TEMPSENSOR ADC value to Temperature in ºC.
 * @param[in] sample ADC_CHANNEL_TEMPSENSOR value read.
 * @return temperature in float.
 * @note This temperature sensor measures junction temperature of the microcontroller.
 * */
float temp_calc(uint16_t sample) {
  /* Factory calibrated values. Address for STM32F072x8 and STM32F072xB. Check datasheet for each microcontroller */
  const uint16_t ADC_TEMP_3V3_30C = *((uint16_t *)(0x1FFFF7B8));
  const float TEMP_30C = 30.0F;
  const uint16_t ADC_TEMP_3V3_110C = *((uint16_t *)(0x1FFFF7C2));
  const float TEMP_110C = 110.0F;
  const float CALIBRATION_REFERENCE_VOLTAGE = 3.3F;
  const float REFERENCE_VOLTAGE = 3.3F;  // Supply voltage at Vref+ or VDDA. Change accordingly.
  /* Scaling calibrated values according to our reference voltage */
  float kAdcCalValue30 = (float)(ADC_TEMP_3V3_30C) *
                        (REFERENCE_VOLTAGE / CALIBRATION_REFERENCE_VOLTAGE);
  float kAdcCalValue110 = (float)(ADC_TEMP_3V3_110C) *
                         (REFERENCE_VOLTAGE / CALIBRATION_REFERENCE_VOLTAGE);
  /* Calculate temperature*/
  float temperature = ((float)(sample)-kAdcCalValue30) /
                          (kAdcCalValue110 - kAdcCalValue30) * (TEMP_110C - TEMP_30C) +
                      TEMP_30C;
  return temperature;
}