DocID022913 Rev 2

13/27

AN4067

Internal RC oscillator calibration

26

Note:

When using an external signal as a reference, another timer can be used instead of TIM14.

The firmware provided with this application note uses TIM14.

Refer to the application note AN2868 “Internal RC oscillator (HSI) calibration” for more

details about using the external signal frequency for calibration.

3.2.3

Measure the HSI14 frequency

The STM32F0xx product family offers a useful feature, that is the ability to connect internally

and indirectly the High-speed internal (HSI14) oscillator to Timer 14 channel 1.

Figure 7 shows the hardware connections needed for internal oscillators calibration.

Figure 9. Hardware connection For HSI14

1.

TI1_RPM: TIM14 input 1 remapping

2.

TI1: Timer input 1

3.

IC1PS: Input capture 1 prescaled

3.3

Description of the internal oscillator calibration firmware

The internal RC oscillator calibration firmware provided with this application note includes 4

major functions:



uint32_t HSI_CalibrateMinError(void)



ErrorStatus HSI_CalibrateFixedError(uint32_t MaxAllowedError,

uint32_t* Freq)



uint32_t HSI14_CalibrateMinError(void)



ErrorStatus HSI14_CalibrateFixedError(uint32_t MaxAllowedError,

uint32_t* Freq)



ErrorStatus HSI_CalibrateCurve( uint32_t* Freq );



void HSI_GetCurve( void );



ErrorStatus HSI14_CalibrateCurve(uint32_t* Freq);



void HSI14_GetCurve(void);



uint32_t HSI48_FreqMeasure( void );



uint32_t HSI48_ManualTrimming( void );