STM32L4 ADC Configuration to read internal temperature sensor's data.

this is the code I use for the F091

void readProcessorTemperature(void) {
 //Temperature computation code example
 // Temperature sensor calibration value address 
#define TEMP110_CAL_ADDR ((uint16_t*) ((uint32_t) 0x1FFFF7C2)) // calibrated at 3.3V +-10mV @110C +/- 5C 
#define TEMP30_CAL_ADDR ((uint16_t*) ((uint32_t) 0x1FFFF7B8)) // calibrated at 3.3V +-10mV @ 30C +/- 5C 
#define VREFINT_CAL ((uint16_t*) ((uint32_t) 0x1FFFF7BA)) // calibrated at 3.3V +-10mV @ 30C +/- 5C 
#define VDD_CALIB ((uint16_t) (3300)) // set in factory
#define VDD_APPLI ((uint16_t) (3295)) // set my measuring my voltage on PCB
	
 	int32_t AveTemperatureADC = ADC_Channel_AVE[VTemp_Ad16]; // 16x over sampled, needs /16
 
 double processorTemp; // the temperature in degree Celsius
 	
 processorTemp = (double) AveTemperatureADC / 16 - *TEMP30_CAL_ADDR;
 processorTemp *= 110 - 30;
 processorTemp /= ((double)*TEMP110_CAL_ADDR) - *TEMP30_CAL_ADDR;
 processorTemp += 30;
 processorTemperature = (int32_t)(processorTemp * 100);
 //printf("AveTemperatureADC %04X, ADC_CalibrationFactor %04X, *TEMP30_CAL_ADDR %04X, processorTemperature %.2f, processorTemp %.3f \n\r",AveTemperatureADC,ADC_CalibrationFactor,(int32_t) *TEMP30_CAL_ADDR,((float)processorTemperature/100),processorTemp);
 
 Vdda = (double)16 * 3.3 * *VREFINT_CAL; // 16x oversampled data requires /16
 Vdda /= ADC_Channel_AVE[VRef_Ad17];
 
 setCursor1(0, 90); // static debug screen
 printf( "processorTemperature %.1f ", ((float)processorTemperature) / 100);
 printf( "Vdda as %.3f \n\r", Vdda);
 
}

Hi @Community member​ ,

you have probably already solved the problem. Just for others that might be roaming here:

1.Sampling time

The constrains are stated in the datasheet (DS11449, section 6.3.23 Temperature sensor characteristics) . The ADC sampling time when reading the temperature >= 5us.

2.Vdda

Attention must be payed to the conditions on when the TS_CAL1 and TS_CAL2 values were acquired.

In the same datasheet as above, section 3.15.1 Temperature sensor says, that the values were obtained with Vdda = 3.0V. If your Vdda is different, then you need to recalculate the TS_CAL1 and TS_CAL2 values accordingly, in order to get correct values.

It seems to me, that you might have faced the mutual effect of those two reasons.

I hope, this answer will help somebody struggling with the same issue here. :)

Best regards,

Michal

Yep, first you have to read Vref, deduct Vdd and scale the ADC from Vdd down to 3.0V to run the linear interpolation.

The ADC example in Cube is not going to bring you to this point.