Bootloader to update firmware via UART: It is possible to invert UART TX pin?

[Guillherme Amaral]

My project requires a RS-232 cable with TX inverted to connect the PC with CubeProgrammer CLI to STM32WB55. In application, I am able to configure the UART with "UART_ADVFEATURE_TXINVERT_INIT", and the STM32WB55 transmission works fine through the RS-232 cable, but does not work on bootloader, since by default the TX pin is not inverted.

Any idea on how to workaround this?

A custom bootloader is an option to consider, but since I am using CubeProgrammer I would like to use the default bootloader from ST.

[Peter BENSCH]

Welcome @Guillherme Amaral​ to the Community!

As you have probably already seen that in AN2606, the built-in bootloader is fixed and doesn't offer configuration parameters, so there is no way to use such special features.

Either you use an external single-gate inverter or you write your own bootloader, which of course reduces your user's Flash area.

Good luck!

When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

/Peter