STM32 f405 processor replacement on Speedybee F405 V4 board

[samsab1]

This is a related request to INAV, but I think all INAV developers should have a relevant experience on the subject, which I'd like to share below:

I want to replace the processor on a Speedybee F405 V4 flight controller, as it became bricked after an update.

I bought this processor on AliExpress, but I have serious doubts about identifying pin #1. The different AIs I've queried give conflicting results, so I'm reaching out to experts for help.

The original flight controller: IMG_20260523_081511.jpg
The processor: ALISd63e9cd9e81e4f36bad9cfaa62129b12K.webp
The same under a microscope: PICA0002.jpg

If I'm not mistaken about the orientation of this chip and the resoldering goes correctly, mathematically, will the board react as it should, meaning it will be visible via the USB port and allow the firmware to be downloaded?

Who can help me with this? Regards

[daijoubu]

You can't brick an stm32 processor. The bootloader is in ROM.

[samsab1]

i have tried all my best, but there was a memory access pb

[sensei-hacker]

If a flash goes bad, hold down the DFU button as you plug in the board. That goes to the factory bootloader, so it doesn't matter what you flashed.

Pin 1 is marked by a small, concave dimple mark on the board. You may see another large, flat circle on the opposite corner. The rounded one is the pin 1 marking.

The big flat one is from the tool that pops the molded chip case out of the mold.