Internal oscillator calibration/measurement example description

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Internal oscillator calibration/measurement example

description

The example provided with this application note shows the ability of the firmware to calibrate

the internal RC oscillators (HSI, HSI14 and HSI48) and explains how to use it to measure

the internal RC oscillators (HSI14 and LSI) of the STM32F0xx microcontroller.

In this example:



After system reset, the HSI is selected to be used as the system clock source.



The HSI is calibrated using the LSE oscillator as a reference clock.



When the HSI oscillator has been calibrated, the PLL (clocked by HSI) is configured to

48 MHz and used as the system clock source.



Then, the HSI14 is calibrated according to HSI precision.



HSI48 is measured and calibrated.



Then HSI48 is selected as system clock, CRS peripheral initialized and run.



After that, the LSI frequency is measured.



Finally, the measured frequency of the different oscillators is displayed on the

STM320518-EVAL board's LCD, as shown in Figure 16.

By default, the example uses the minimum error method to calibrate the HSI and HSI14

oscillators.

To run the calibration process that provides the frequency with fixed error, users have to

comment out the following define in the main.c file:

#define CALIBRATION_MIN_ERROR

Figure 16. Internal oscillator calibration