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Problem talking to STM32F091 bootloader.

MFord.1
Associate III

Hi there,

The goal I am trying to achieve is putting myself into bootloader mode through software (using the option bytes and not boot pin). I was able to successfully do this with a STM32L071 I was using before.

Currently I cannot communicate with the bootloader, even though I am pretty sure I am entering bootloader mode (program in flash is not being executed).

0693W000001r0yuQAA.png

I am using row 5 configuration so I do not have to worry about the Boot pin.

As I stated before, I believe I am entering into the bootloader mode I just cannot talk to the bootloader. I get errors when trying to connect using the STM flash tool or just sending the 0x7F first byte myself (no response when I send it myself).

I am honestly baffled but I came across what seems like a discrepancy in the documentation that may affect my implementation. I am using USART2 using pins PA2 and PA3 to try and communicate with the bootloader.

0693W000001r11tQAA.png

From the AN2606 application notes it seems like you can use PA2 and PA3 for USART2 to communicate to the bootloader (what I am trying to do).

0693W000001r12mQAA.png

From the RM0091 reference manual for STM32F0x1 devices, among others, it does not mention the PA2 and PA3 for USART2, only PA 14 and PA15 for USART2 and PA9 and PA10. It then mentions AN2606 which references PA2 and PA3.

0693W000001r14EQAQ.png

Lastly the specific datasheet for STM32F0xB and xC only mentions PA14 PA15 and PA9 PA10.

(https://www.st.com/content/ccc/resource/technical/document/datasheet/95/3c/2e/5b/21/09/45/a6/DM00115237.pdf/files/DM00115237.pdf/jcr:content/translations/en.DM00115237.pdf)

Which one should I believe or has anyone encountered this before? The application note lists the port I am using as an option and the other two do not. Unfortunately I cannot try the other pins at the moment, they are already populated on the PCB.

Any advice is appreciated! Also if you have any other ideas as to why I can't talk to the bootloader, that would be great as well!

Thanks

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