CalibrationThe ADC has an built-in self calibration mode. Calibration significantly reduces accuracyerrors due to internal capacitor bank variations. During calibration, an error-correction code(digital word) is calculated for each capacitor, and during all subsequent conversions, theerror contribution of each capacitor is removed using this code.Analog-to-digital converter (ADC)Calibration is started by setting the CAL bit in the ADC_CR2 register. Once calibration isover, the CAL bit is reset by hardware and normal conversion can be performed. It isrecommended to calibrate the ADC once at power-on. The calibration codes are stored inthe ADC_DR as soon as the calibration phase ends.Note:1 It is recommended to perform a calibration after each power-up.2 Before starting a calibration the ADC must have been in power-off state (ADON bit = '0') forat least two ADC clock cycles.