LSE OSC32 not starting oscillation

[Sylvain Kaempfer]

Posted on December 16, 2016 at 14:27

Hello,

I recently bought some stm32f303vct6 for a clock project. I first made a version for the stm32f3discovery board and my program worked, then I tried to program a microcontroller who isn�t on the discovery board everything work except that the LSE doesn�t start to oscillate. I tried to change my capacitor but nothing changed.

Can someone help me?

Best Regards

Sylvain

PS: I use CubeMX to generate the initialization code

#lse-osc32-not-starting-oscillation

[Walid FTITI_O]

Posted on December 16, 2016 at 20:12

Hi

sylvain

,

You should checkif the new LSE source (crystal/oscillator) is correct - > check the table.7 of application note

http://www.st.com/content/ccc/resource/technical/document/application_note/c6/eb/5e/11/e3/69/43/eb/CD002216pdf/files/CD002216pdf/jcr:content/translations/en.CD002216pdf

Second, the used project generated from the CubeMx is for the STM32F3-Disco hardware ; the workspace will include many HW dependencies you would check -> I advise you to regenerate another project using the .ioc file with selection you new board or simply the device.

-Walid F-

[Sylvain Kaempfer]

Posted on December 17, 2016 at 16:40

Hi Walid F

Thank you for answering. I'm sure that the new LSE source is correct. For the second part I’m not able to test it until Tuesday.

Best regards

Sylvain

[Tesla DeLorean]

Posted on December 20, 2016 at 13:59

The STM32 devices don't function properly with the 9pF and 12pF 32.768 KHz crystals that are quite common. You want one of the 6-7pF variety, and review the performance of the circuit with the components as built. The most common failures are taking a long time to start, or not starting, and frequency being off or unstable.