Re:Chaining USB drives
by dangrossman on Thursday November 24, 2011 @11:27PM
(#3276212)
For it to work, each of the drives would have to be both a mass storage device and a USB hub. Can USB hubs be this small? If each segment has to be 3 inches long to accomodate the dual functionality, a foot long chain of USB drives sticking out the side of your laptop is a bit less elegant than the concept.
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I don't think size would be much of an issue. Random googling finds USB2512[1] which comes in a 6mm x 6mm QFN package. It needs a crystal and a few caps. There's probably an equally tiny flash + USB SoC around to bolt onto it.
The hard part would be the board layout (USB2 requires some line impedance matching, afaik) and the actual packaging.
I reckon you could (conservatively) fit the necessary circuitry into 1 or 2 microSD sized cuboids, maybe one above the plug/socket, and one below. Maybe even less if you eschew some of the spec and only support daisy-chaining your own devices.
There's also the problem of power. I doubt these devices could be usb spec compliant since what is essentially happening here is an endless chain of bus powered usb hubs.
It is pretty though.
It's not even the first time it was "dreamed" by some designer, with no technical consideration. You cannot actually do that in a standard way. Dan has a nice article on this:
http://dansdata.blogsome.com/2010/03/23/for-suitably-small-v...