Using The Mass Storage Bootloader - Adafruit Feather M4 Express Manual

Once the bootloader is successfully connected you can open the drive and browse the virtual filesystem. This isn't the
same filesystem as you use with CircuitPython or Arduino. It should have three files:
CURRENT.UF2 - The current contents of the microcontroller flash.
INDEX.HTM - Links to Microsoft MakeCode.
INFO_UF2.TXT - Includes bootloader version info. Please include it on bug reports.

Using the Mass Storage Bootloader

To flash something new, simply drag any UF2 onto the drive. After the file is finished copying, the bootloader will
automatically restart. This usually causes a warning about an unsafe eject of the drive. However, its not a problem. The
bootloader knows when everything is copied successfully.
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