fleg
/
OpenRTX
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Stm32 ADC: increased measurement accuracy 

Increased accuracy of ADC measurements by applying a correction factor for
the real value of VDDA/VREF+, computed using the internal voltage reference.
This commit is contained in:
Silvano Seva 2024-11-10 11:30:42 +01:00
parent 3ff2d31a70
commit df5d6dccef
1 changed files with 27 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
platform/mcu/STM32F4xx/drivers/adc_stm32.c
View File

@ -21,6 +21,13 @@
#include <errno.h> #include <errno.h>
#include "adc_stm32.h" #include "adc_stm32.h"
// Internal voltage reference calibration value, measured with Vref = 3.3V
// at 30°C. See Table 73 in STM32F405 datasheet
static const uint16_t *vRefCal = (uint16_t *) 0x1FFF7A2A;
static uint16_t vrefInt = 0;
uint16_t adcStm32_sample(const struct Adc *adc, const uint32_t channel);
int adcStm32_init(const struct Adc *adc) int adcStm32_init(const struct Adc *adc)
{ {
switch((uint32_t) adc->priv) switch((uint32_t) adc->priv)
@ -64,6 +71,14 @@ int adcStm32_init(const struct Adc *adc)
pAdc->SQR1 = 0; pAdc->SQR1 = 0;
pAdc->CR2 = ADC_CR2_ADON; pAdc->CR2 = ADC_CR2_ADON;
// Read internal voltage reference
if((uint32_t) pAdc == ADC1_BASE)
{
ADC123_COMMON->CCR |= ADC_CCR_TSVREFE;
vrefInt = adcStm32_sample(adc, 17);
ADC123_COMMON->CCR &= ~ADC_CCR_TSVREFE;
}
if(adc->mutex != NULL) if(adc->mutex != NULL)
pthread_mutex_init((pthread_mutex_t *) adc->mutex, NULL); pthread_mutex_init((pthread_mutex_t *) adc->mutex, NULL);
@ -116,7 +131,7 @@ uint16_t adcStm32_sample(const struct Adc *adc, const uint32_t channel)
while((pAdc->SR & ADC_SR_EOC) == 0) ; while((pAdc->SR & ADC_SR_EOC) == 0) ;
uint16_t value = pAdc->DR; uint32_t value = pAdc->DR;
/* Disconnect Vbat channel. Vbat has an internal x2 voltage divider */ /* Disconnect Vbat channel. Vbat has an internal x2 voltage divider */
if(channel == 18) if(channel == 18)
@ -125,5 +140,15 @@ uint16_t adcStm32_sample(const struct Adc *adc, const uint32_t channel)
ADC123_COMMON->CCR &= ~ADC_CCR_VBATE; ADC123_COMMON->CCR &= ~ADC_CCR_VBATE;
} }
return value; /*
* Apply the Vref correction, if present.
* NOTE: this is valid only if VDDA/VREF+ is connected to 3.3V
*/
if(vrefInt != 0)
{
value *= (*vRefCal);
value /= vrefInt;
}
return (uint16_t) value;
} }