STM32H5763IIK, Bootloader v14
I'm planning on using USART1 and USART3 in my application. I'd like to be able to access the bootloader from both. The bootloader documents say that USART2 and USART3 at very least use pins that are not attached to their respective modules.
On the chip, USART1 can be:
TX PA9, PB6, PB14
RX PA10, PB7, PB15
The bootloader note AN2606 says the H5763 USART1 uses: A9/A10 which are valid options! No issue.
For USART3 the chip can operate on:
TX PB10, PC10, PD8
RX PB11, PC11, PC4, PD9
AN2606 says USART3 can use: None of those pairs... uses PD9 ok, but also PA4 which isn't associated to UART3 at all.
Applies to USART2 as well.
- I've checked all of the alternate function lists and verified at least CAN and USB have seemingly correct line ups. Didn't look at SPI or I(2/3)C.
- The only way I think this can happen is if the bootloader's code defines and uses software UART TX. Where at least the TX pins aren't driven by hardware but bit-banging out their signals. I can not imagine why this would be the case, some peripherals use the correct pins, and others do not, for software reasons?
- As a workaround USART2, I could use RX PA3 / TX PA2 and PA5 so that when the bootloader is running it uses PA5, but in the application I use hardware an PA2. Uses an extra pin only for bootloader, and that's fine so long as I know this limitation / configuration is real.
- I would be less surprised if the list of bootloader pins was just incorrect.
I need someone from ST to confirm that AN2602 (Page 250) matches up with reality.
AN2602: https://www.st.com/resource/en/application_note/cd00167594-stm32-microcontroller-system-memory-boot-mode-stmicroelectronics.pdf
Datasheet: https://www.st.com/resource/en/datasheet/stm32h563ii.pdf
