Hi Mam/ Sir, I am using STM32F779 MCU in that OSC(RTC) clock is not working(output wave not coming), so please suggest any hardware & software settings needed I attached schematic

[Pkuma.41]

For OSC i am using 32.768khz and caps 10pF, but output is not coming. so please give me suggestions for hardware & software chages to work 32.768khz clock work.

[Tesla DeLorean]

What's the crystal part# ? Is it a 6, 9 or 12 pF crystal? Capacitors calculated per Application Note?

Should be able to walk-in the LSE enable via RCC/PWR register bits. Should be able to route the LSE clock via MCO1 / PA8 to measure without loading the circuit.

[Pkuma.41]

Hi Tesla,

Thanks for your response.

Crystal Part: CM315D-32.768KDZC-UT

Please share cap values to above crystal part for hardware changes.

[Tesla DeLorean]

Surely you should be able to run your own numbers?

I'd perhaps try 4.7pF or 5.1pF

Run a simple application to enable the clocks, and plumb the output to the MCO1 (PA8) pin.

[Pkuma.41]

Thank you, Tesla.

I will test and come back to you.

[Pkuma.41]

@Hi Tesla,

I attached scope image of PA8 output, but signal is in square wave and F= 32.72khz coming instead of 32.768khz.

Need some more changes required for exact clock 32.768khz ?

[Fgfdh.1]

I am also using STM32F779 MCU in that OSC(RTC) clock is not behaving well please guide me the reason of this issue you can see here the details in my account.

[Pkuma.41]

Hi Tesla,

I mounted 5pF CL caps still not get proper clock on crystal. Please suggest need software configurations required images attached.

[Pkuma.41]

Clock internal resistance setting required ?

[Pkuma.41]

In datasheet recommended cap table

[Pkuma.41]

STM recommended crystal used on my board: CM315D

Part in application note(AN2867)