Baud rate errors
With your description, it more like a bug in HAL lib. You may discuss it to ST support, as the HAL lib is provided by ST.
BTW,I had experienced some issues on UART baud rate issue on STM32. On STM32F0Discovery board, which is only HSI available, I can easily to configure/run the USART1 and 2 on UART mode with baud rate to 921600; but on STM32F4Discovery board, which has external oscillator available, I have to sacrifice Usb clock and make same other tweaking on clock settings to make UART rate above 115200.
BBlue
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