[MisterTea]

The flash on the mbed was a real 2MB FAT disk that you could upload one or more random files to, not just mbed binaries. I assume they built a dual ported flash driver that arbitrates access between the loader and the USB storage driver. I should also mention it looked for .bin files and checked the mtimes to load the newest .bin file in the disk's root. So it was using a real FAT file system on both ends.