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Question about HSE and LSE

Associate III

Hello guys. I'm trying to design a custom pcb that uses an STM32h7a3zit mcu and one of the most confusing parts is clock configuration. I will mainly use the hs usb interface. I've searched a couple of online sources and from what i could find is that i should configure the clock as follows :


Στιγμιότυπο οθόνης (701).png


Στιγμιότυπο οθόνης (700).png


The LSE is set to Crystal/ Ceramic Resonator and the corresponding Mux is set to LSI meaning that it will use an internal clock.

The HSE is set to Bypass clock source meaning that it should use an external oscillator. I currently use a nucleo board and  the manual states that there is no such component on board (X2). Does it use the X1 component that goes through the STLINK(U14) instead? Can i just connect the X1 unit straight to the mcu, given that i don't need an onboard STLINK on my custom board ? In addition the clock should be set to HSE but it is set to HSI instead.


The NUCLEOs source a crystal clock via the MCO pin of the ST-LINK's STM32. You can disconnect that and place parts to provide a local oscillator for the Target STM32 or use a crystal or TCXO in your own design.

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