STM32F2 RTC coarse calibration seems to have no effect

mmensch · ‎2016-02-11

Posted on February 11, 2016 at 10:29

Hi,

on a STM32F207 I want to use coarse calibration but it seems to have no effect.

- I changed PRER to PREDIV_A = 63 and PREDIV_S = 511 and print it out on a UART after reset. I changed to these values to have a better calibration resolution. This is how I understand chapter 22.3.9 of STM32F205 207 ref manual.

- Still I have 512 Hz at the calibration output, though chapter 22.3.12 in ref manu implies that the frequency depends on PREDIV_A, following this I would expect 1024 Hz

- for several weeks I changed CALIBR but always have the RTC running about 20 ppm too fast (eg. 12 sec in 6.8 days). Now I reached CALIBR = 0x9F, I also print this out after reset. As far a I understood I should have a slow down of the RTC of 31 ppm with these settings, but no success.

Is there any setting I need to make to enable coarse calibration? Or do I need the standard values in PRER? Any other ideas?

Thanks a lot

Martin

#rtc-stm32f2-calibration

mmensch · ‎2016-02-14

Posted on February 15, 2016 at 08:52

just pushing this up again

Any ideas ?

Does anybody have a good experience with coarse RTC calibration? I would be glad to hear some details about it.

Thanks a lot

Martin

Tesla DeLorean · ‎2016-02-15

Posted on February 15, 2016 at 12:58

Would suggest you chat with your local FAE

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b_ · ‎2016-10-14

Posted on October 14, 2016 at 10:58

Hi Mr M from G

I'm facing the same problem do you have any news for us?

Thank you very much!

Cheers

B from S