I have got some good news:
1) Adding delays in the generated HAL calibration function between enable and disable ADC stages as per thread you pointed, is fixing the calibration problem and the ADC is starting and it is working as normal after the calibration.
/**
* @brief Perform an ADC automatic self-calibration
* Calibration prerequisite: ADC must be disabled (execute this
* function before HAL_ADC_Start() or after HAL_ADC_Stop() ).
* @note Calibration factor can be read after calibration, using function
* HAL_ADC_GetValue() (value on 7 bits: from DR[6;0]).
* @PAram hadc ADC handle
* @retval HAL status
*/
HAL_StatusTypeDef HAL_ADCEx_Calibration_Start(ADC_HandleTypeDef *hadc)
{
HAL_StatusTypeDef tmp_hal_status;
__IO uint32_t wait_loop_index = 0UL;
uint32_t backup_setting_cfgr1;
uint32_t calibration_index;
uint32_t calibration_factor_accumulated = 0;
uint32_t tickstart;
/* Check the parameters */
assert_param(IS_ADC_ALL_INSTANCE(hadc->Instance));
__HAL_LOCK(hadc);
/* Calibration prerequisite: ADC must be disabled. */
/* Disable the ADC (if not already disabled) */
tmp_hal_status = ADC_Disable(hadc);
// A minimum delay is required after enabling or disabling the ADC
HAL_Delay(1);
/* Check if ADC is effectively disabled */
if (LL_ADC_IsEnabled(hadc->Instance) == 0UL)
{
/* Set ADC state */
ADC_STATE_CLR_SET(hadc->State,
HAL_ADC_STATE_REG_BUSY,
HAL_ADC_STATE_BUSY_INTERNAL);
/* Manage settings impacting calibration */
/* - Disable ADC mode auto power-off */
/* - Disable ADC DMA transfer request during calibration */
/* Note: Specificity of this STM32 series: Calibration factor is */
/* available in data register and also transferred by DMA. */
/* To not insert ADC calibration factor among ADC conversion data */
/* in array variable, DMA transfer must be disabled during */
/* calibration. */
backup_setting_cfgr1 = READ_BIT(hadc->Instance->CFGR1, ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | ADC_CFGR1_AUTOFF);
CLEAR_BIT(hadc->Instance->CFGR1, ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | ADC_CFGR1_AUTOFF);
/* ADC calibration procedure */
/* Note: Perform an averaging of 8 calibrations for optimized accuracy */
for (calibration_index = 0UL; calibration_index < 8UL; calibration_index++)
{
/* Start ADC calibration */
LL_ADC_StartCalibration(hadc->Instance);
/* Wait for calibration completion */
while (LL_ADC_IsCalibrationOnGoing(hadc->Instance) != 0UL)
{
wait_loop_index++;
if (wait_loop_index >= ADC_CALIBRATION_TIMEOUT)
{
/* Update ADC state machine to error */
ADC_STATE_CLR_SET(hadc->State,
HAL_ADC_STATE_BUSY_INTERNAL,
HAL_ADC_STATE_ERROR_INTERNAL);
__HAL_UNLOCK(hadc);
return HAL_ERROR;
}
}
calibration_factor_accumulated += LL_ADC_GetCalibrationFactor(hadc->Instance);
}
/* Compute average */
calibration_factor_accumulated /= calibration_index;
// A minimum delay is required after enabling or disabling the ADC
HAL_Delay(1);
/* Apply calibration factor */
LL_ADC_Enable(hadc->Instance);
// A minimum delay is required after enabling or disabling the ADC
HAL_Delay(1);
LL_ADC_SetCalibrationFactor(hadc->Instance, calibration_factor_accumulated);
// A minimum delay is required after enabling or disabling the ADC
HAL_Delay(1);
LL_ADC_Disable(hadc->Instance);
// A minimum delay is required after enabling or disabling the ADC
HAL_Delay(1);
/* Wait for ADC effectively disabled before changing configuration */
/* Get tick count */
tickstart = HAL_GetTick();
while (LL_ADC_IsEnabled(hadc->Instance) != 0UL)
{
if ((HAL_GetTick() - tickstart) > ADC_DISABLE_TIMEOUT)
{
/* New check to avoid false timeout detection in case of preemption */
if (LL_ADC_IsEnabled(hadc->Instance) != 0UL)
{
/* Update ADC state machine to error */
SET_BIT(hadc->State, HAL_ADC_STATE_ERROR_INTERNAL);
/* Set ADC error code to ADC peripheral internal error */
SET_BIT(hadc->ErrorCode, HAL_ADC_ERROR_INTERNAL);
return HAL_ERROR;
}
}
}
/* Restore configuration after calibration */
SET_BIT(hadc->Instance->CFGR1, backup_setting_cfgr1);
/* Set ADC state */
ADC_STATE_CLR_SET(hadc->State,
HAL_ADC_STATE_BUSY_INTERNAL,
HAL_ADC_STATE_READY);
}
else
{
SET_BIT(hadc->State, HAL_ADC_STATE_ERROR_INTERNAL);
/* Note: No need to update variable "tmp_hal_status" here: already set */
/* to state "HAL_ERROR" by function disabling the ADC. */
}
__HAL_UNLOCK(hadc);
return tmp_hal_status;
}
2) Having the calibration completed with a calibration factor result of 64, now the ADCrefint reads at 377 which converts to 1.215V which seems more reasonable value.
3) The embedded internal voltage reference set during production reads as 1655, not sure what that means, and the comment in the source code I find the register address says:
/* ADC internal channels related definitions */
/* Internal voltage reference VrefInt */
#define VREFINT_CAL_ADDR ((uint16_t*) (0x1FFF75AAUL)) /* Internal voltage reference,
address of parameter VREFINT_CAL: VrefInt ADC raw data acquired at temperature 30 DegC (tolerance: +-5 DegC),
Vref+ = 3.0 V (tolerance: +-10 mV). */
