Struggling getting STM32F405 into DFU to Flash

[dmairq]

I just bought the Feather STM32F405 and I'm trying to get into DFU mode to flash CircuitPython. No matter what I do I can't get this to be recognized to flash it. I've tried different Macs and Windows and I never can get it to show up as a DFU device. I know that I have to force B0 high and apply power or reset. I've tried this too many times to even count without success. If I attach the jumper and apply power the large color led remains off while the tiny yellow light next to the USB flashes quickly and no USB device shows up in the device tree. Only after releasing the jumper the color LED starts to color cycle but the device in the USB device tree says FEATHER_F405 CDC in FS Mode. I think we want to see that in DFU mode. I've also tried this while having the jumper on when already powered and hitting reset. The color LED stops at whatever color it was cycling through and the tiny yellow light just flashes. Nothing Feather related shows in the USB device tree. As soon as I remove the jumper, the LED starts to color cycle and it shows FEATHER_F405 CDC in FS Mode. I've tried dfu-util and the windows STM32 cube application and just can't get a DFU device recognized. I've searched around and see a lot of people struggling but no solution. Was excited to try a new smoking fast Feather but struggling to get it flashed with Circuit Python. Need some ideas....

[dmairq]

Well that was weird... I was so frustrated I had to just walked away from it for maybe 15 minutes. I happened to leave the B0 jumper on and when I came back and refreshed the device tree magically the STM32 BOOTLOADER device showed up. I've tried leaving the jumper on before but maybe for not as long. Specifically the steps were:

While powered up and connected on USB.
Pushed B0 high, hit reset and set the board down with B0 still connected.
Walked away for 10-15 minutes.
Came back and refreshed device tree on Mac.
Device was in DFU
Ran dfu-util and flashed circuit python while the B0 cable still connected. Flashed fine.
Pulled the jumper, hit reset and CIRCUITPY showed up.

Adafruit - You really need to put a note in the tutorials that this device might torture you going into DFU. I hope I never have to upload again. I would not even consider this device for anything but Circuit Python with the level of difficulty getting it into DFU each time.

[ilium007]

Had issues entering DFU as well.... no updates from Adafruit on what the bug is.

viewtopic.php?f=57&t=175709

[adafruit_support_mike]

We haven’t been able to reproduce the issue on our own hardware, so all we can offer is speculation.

We’ll keep reading reports from people who run into it, and will follow any leads we can find, but right now we’re at “something happens, we don’t know what or why, and sometimes it goes away on its own”.