Hello,
I am using a NUCLEO-STM32H753ZI-$AT3 development board.
When I configure the MCU to use the internal clock (HSI), everything works correctly and my UART debug logs are printed normally.
However, when I switch to using the external 25 MHz clock (HSE), no UART logs are printed. The code runs,but the UART prints garbage characters, for example:
<0x1c><0xe0><0xfc><0x1c><0xe
What I have already checked:
25 MHz external clock is selected in CubeMX (HSE ON, Crystal/Ceramic Resonator).
PLL settings are unchanged except switching HSI → HSE.
UART baud rate is the same (115200).
If I go back to internal HSI, UART prints again.
External clock ioc and log
Iternal clock ioc and log
