DocID027266 Rev 2

13/30

Internal RC oscillator calibration

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2.3

Description of the internal oscillator calibration firmware

The internal RC oscillator calibration firmware provided with this application note includes

three major functions:

•

uint32_t

HSI16_CalibrateMinError(void)

•

ErrorStatus HSI16_CalibrateFixedError(uint32_t MaxAllowedError,

uint32_t* Freq)

•

ErrorStatus HSI16_CalibrateCurve(uint32_t* Freq)

•

uint32_t

MSI_CalibrateMinError(void)

•

ErrorStatus MSI_CalibrateFixedError(uint32_t MaxAllowedError,

uint32_t* Freq)

•

ErrorStatus MSI_CalibrateCurve(uint32_t* Freq)

•

void HSI16_GetCurve( void );

•

void MSI_GetCurve(void);

•

uint32_t HSI48_FreqMeasure( void );

•

uint32_t HSI48_ManualTrimming( void );

2.3.1

HSI16/MSI calibration with minimum error

The HSI16_CalibrateMinError() and MSI_CalibrateMinError() functions calibrate the internal

oscillator to have the frequency nearest to the typical value. It measures all frequencies for

different trimming values and provides the trimming value that corresponds to the frequency

with the minimum error. The trimming value thus obtained is programmed in the trimming

bits.

After calibration, the HSI16_CalibrateMinError() and MSI_CalibrateMinError functions return

the internal oscillator frequency value as an unsigned 32-bit integer (uint32_t).

The flowchart in Figure 8 provides the algorithm for this function.

Example

uint32_t InternOscAfterCalib = 0;

{

......

/* Get the internal oscillator (HSI16) value after calibration */

InternOscAfterCalib = HSI16_CalibrateMinError();

}