Bootloader Indication LED

[shaling]

Hi,

I have the STM32H753ZI Nucleo board and have developed firmware around this MCU with this board as my reference platform.
On our product, firmware updates will be uploaded via the UART interfaces.
So the user will need to enter Bootloader.
On the Nucleo board, the LD3 Red LED stays illuminated when in Bootloader.
I think this is because the GPIO pin is being pulled up, and this is not intentional as an indicator?
An indication to the user that they have successfully reset the MCU into Bootloader is useful.
How can you recommend we can do this in a reliable way in the future?
Thanks.

[Uwe Bonnes · Accepted solution]

According to AN2606 PB14 is USART1 TX (alternate) and set to push pull during system bootloader. TX inactive level is high and so Q3 will conduct and LD3 light up.

[shaling]

That explains it. Thanks very much. I can use this :).

Much appreciated.