How to make a cable adapter with Micro SD to Mini USB! It will be connected instead of a flash drive external HDD!
Well, actually, just the cable will not work . Because for SD to work, you need a controller ... And another USB controller ... And so on. Those. it will not be an adapter cable anymore, but a card reader. It is cheaper to buy a ready-made card reader for micro SD ...
Cheaper to buy Chinese.
But if you are interested in samopal, then you take arm7 / arm9 with built-in usb2.0, see the mass storage device implementation example, write or take a ready-made library for SD-cards (from the same elm-chan, or EFSL).
Well, add interaction between them. But do not count on speed)