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drivers: adc: stm32: Add STM32h7xx linearity calibration

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The STM32H7 series has a special ADC, which is calibrated
on the factory. The calibration values are stored in flash
and must be retrieved upon powering up the device.

Failure to calibrate the device leads to missing codes in
the ADC readings.

Fixes #35529

Signed-off-by: Lasse Sangild <lsangild@gmail.com>
This commit is contained in:
Lasse Sangild 2021-05-25 10:05:57 +02:00 • committed by Carles Cufí
commit e4463a7d9e
1 changed files with 27 additions and 0 deletions
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27
drivers/adc/adc_stm32.c
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@ -787,6 +787,33 @@ static int adc_stm32_init(const struct device *dev)
LL_ADC_StartCalibration(adc);
LL_ADC_REG_SetTriggerSource(adc, LL_ADC_REG_TRIG_SOFTWARE);
#endif
#ifdef CONFIG_SOC_SERIES_STM32H7X
/*
* To ensure linearity the factory calibration values
* should be loaded on initialization.
*/
uint32_t channel_offset = 0U;
uint32_t linear_calib_buffer = 0U;
if (adc == ADC1) {
channel_offset = 0UL;
} else if (adc == ADC2) {
channel_offset = 8UL;
} else /*Case ADC3*/ {
channel_offset = 16UL;
}
/* Read factory calibration factors */
for (uint32_t count = 0UL; count < ADC_LINEAR_CALIB_REG_COUNT; count++) {
linear_calib_buffer = *(uint32_t *)(
ADC_LINEAR_CALIB_REG_1_ADDR + channel_offset + count
);
LL_ADC_SetCalibrationLinearFactor(
adc, LL_ADC_CALIB_LINEARITY_WORD1 << count,
linear_calib_buffer
);
}
#endif
adc_context_unlock_unconditionally(&data->ctx);
return 0;