Arduino for STM32

Hello everybody,

I'm using an STM32F103C8 board on a PCB. All the pins on the STM32F103C8 are soldered to the PCB, including PC14 and PC15.

The frequency from the LSE clock is such that it loses about 2 minutes per day, which is enormous. Do you think this is due to the parasitic capacitances added by the PCB, or is it another reason ?

Best regards.

Pierre.

A crystal with 20 ppm should have a deviation of 1,7 s per day. May be more, if board is not working at room temperature.
You are not the first here with LSE problems on a STM32F103 ...

1. Sure you activated LSE?
2. May be crystal is damaged?
3. Stray capacity can have an effect. I would guess, the short lines to pinheader and pins have something below 5 ~ 8 pF.
4. You can cut lines to pinheader and observe, if it's getting better.
5. Or you can take another board to compare.

AN2867 Guidelines for oscillator design

there are some codes for adjusting LSE for RTC on stm32f103 in libmaple core
https://github.com/rogerclarkmelbourne/ ... /RTCAdjust
but that you would need to port that code over to stm core if you want to use it

i used it to adjust cheap Alix crystals that are sometimes wildly off
https://www.aliexpress.com/w/wholesale-32768.html

alternatively, get a better crystal

Hello everybody

The last measurement I took showed a loss of 3 minutes over one day.

Not knowing if I was going to succeed, I set about desoldering pins PC14 and PC15 between the STM32 board and the PCB. Not easy, but I succeeded.

But what a satisfaction ! Since yesterday, my LSE clock has lost only one second.

Best regards.

Pierre.

ag123 wrote: Mon Sep 30, 2024 1:38 am there are some codes for adjusting LSE for RTC on stm32f103 in libmaple core
https://github.com/rogerclarkmelbourne/ ... /RTCAdjust
but that you would need to port that code over to stm core if you want to use it

i used it to adjust cheap Alix crystals that are sometimes wildly off
https://www.aliexpress.com/w/wholesale-32768.html

alternatively, get a better crystal

Easy to find information on github page through keywords. The sources you update are really great!