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Nucleo-144 STM32H755ZI vs STM32F767ZI

lserrnt
Associate II

Hey there,

I am facing a problem with the clocks on the STM32H755ZI. When I let a timer run at 50 kHz I get only smt. like 49.92 kHz out of it with sigma = 13 Hz. So there is at any frequency a steady offset of -1.2% and a sigma deviation of 0.03%. I have chosen as HSE the Crystal/Ceramic Resonator and the APB2 of the timer runs at 200 kHz.

lserrnt_0-1694156704155.png

With the Nucleo 144 STM32F767ZI I get for similar settings basically 0% frequency offset and sigma deviation of only 0.0003%. So I am wondering what has changed between these discovery boards

H755:

lserrnt_1-1694156832487.png

https://www.st.com/en/evaluation-tools/nucleo-h755zi-q.html

 

F767:

lserrnt_2-1694156898240.png

https://www.st.com/en/evaluation-tools/nucleo-f767zi.html

they both have this X4 crystal at 25.000 MHz and several others.

So do you see any way how I can achieve a higher frequency stability? Or what I might have to change in CubeIDE to activate a more accurate crystal on the H755 board? 

Thanks a lot for any help 🙂

10 REPLIES 10

I will recheck in future with an external crystal as X2. Thank you for your help 🙂