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I am trying to enter the bootloader of an STM32F103 to flash it via USB. I am pulling BOOT0 high and have pulled B00T1 to low. Based on AN2606, this should get me into the bootloader.

However, I am not seeing the device popup on dmesg or lsusb. I have confirmed there is 3.3 V at the BOOT0 pin on the microcontroller with USB plugged in.

I suspect I have made a mistake on my schematic or maybe I've killed the chip... Hopefully it is straightforward.

Relevant parts of my schematic:

Enter image description here

What should I do?

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  • \$\begingroup\$ Can you show the schematic with NRST signal? Maybe it is pulled down, keeping the device in reset. \$\endgroup\$ Commented Jan 31, 2022 at 8:51
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    \$\begingroup\$ @PierreOlivier NRST is floating. Justme has the right answer, the chip doesn't support usb flashing. \$\endgroup\$
    – seb9usb
    Commented Jan 31, 2022 at 9:19

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The MCU most likely enters bootloader just fine.

It just won't show up as an USB device, as the STM32F103 built-in bootloader has no USB support. This can be verified from the AN2606 you mentioned.

It can't be programmed via USB, unless you flash it with a custom bootloader that does support USB.

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  • \$\begingroup\$ Wow, I did not read AN2606 properly... Will be paying close attention in the future. Cheers \$\endgroup\$
    – seb9usb
    Commented Jan 31, 2022 at 9:20
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    \$\begingroup\$ The blue pill boards, which use this mcu, have a pre-installed bootloader that does support usb, so that may account for the confusion. But the reference manual and datasheet for the part will be clear (particularly when you compare it to other parts that do have usb support in the boot loader), that there is no usb support from the ST programmed bootloader. If you use that arduino sandbox bootloader to program a blue pill and the firmware you programmed does not itself have the usb support then you have to use swd or the st bootloader. \$\endgroup\$
    – old_timer
    Commented Jan 31, 2022 at 9:42

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