Unable to find pin B12 (BOOT0) on B-L47E-IOT01A2

[RBair.3]

Hi everyone,

Something weird happened while I was uploading to my board. The upload crashed half way through and now the USB STLink interface isn't recognized. I think I should be able to upload a working ELF file in UART mode, but to do that I need to boot into bootloader. The user manual indicates that BOOT0 is tied to GPIO B12 (PB12), but I can't find that on the board anywhere. There is a solder bridge for the purpose as well, but I would much rather just use the GPIO. Does anyone have experience with this board who can tell me which pin I need to bridge to get into bootloader mode?

[RomainR. · Accepted solution]

Hello RBair.3 (Community Member)

To understand your need, please confirm that you want to recover the firmware of the main device (STM32L475VGT U1) of the Board using the UART and the bootloader?

If so, its BOOT0 pin is 94, it is by default at GND by SB13 (closed). You can bridge this input to the VDD by closing SB9 and opening SB13.  

The GPIO PB12 (label ISM43362-BOOT0) is in fact used as an interface with the wifi module ISM43362-M3G-L44M2 to update its firmware (this one also contains an STM32 as a coprocessor) it does not allow you to put the STM32L475VG in bootloader mode.

Best regards,

Romain,

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