Re: Building your own flash drive

"Jim Yanik" <jyanik@xxxxxxxxx> wrote in message
news:Xns99E2EEBA93507jyanikkuanet@xxxxxxxxxxxxxx
I wonder if one of the photo mass storage modules would work better than
USB flashdrives?

If you're "rolling your own" interface and code, compact flash looks just like
an IDE hard drive. A USB memory stick, however, only looks like a hard drive
after you get the USB stack and correct protocol all implemented. I.e., much
more software to write.

SD cards are a little weird, AFAIK -- they complete interface at the "wire"
level is not fully available without NDAs and whatnot, although the SD card
readers use an IC that makes the SD card appear, again, as an IDE hard drive
on the far side of a USB link. Hence only the guy who made the USB<-->SD
interface IC needed to sign all those NDAs...

I suspect that the add-on
reader/writers for these are just simple connections to the USB cable.

No, not at all; the interface ICs for SD cards or USB memory sticks are plenty
complex.

There are SD cards
(http://www.sandisk.com/Products/Catalog(1096)-SanDisk_Ultra_II_SD_Plus_Cards.aspx)
and even CompactFlash cards where they've put that "controller" IC into the
memory card into, and thus the SD card can plug directly into a USB port as
well (and the CompactFlash card reader really was little more than "wires"),
but these are very much the exception rather than the norm. (It never really
made sense for CompactFlash cards either, since unlike the SD card shown at
the link above you still need the mechanical adapter... the idea originally
was apparently that, say, 128MB CF card w/internal USB bridge & mechanical
adapter might be, say, $120 whereas a regular 128MB CF card was, say, $100 and
a full-fledged reader was $80.)

Just add a socket on the PCB.I supose you could solder them in,too.

Indeed -- this is a good idea. It's amazing how cheap flash memory is these
days... It was only something like 5 years ago that we were paying something
like $10 a 2MB flash IC, and today you can get something around a gigabyte for
that much in the form of an SD card or USB memory stick.

---Joel


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Relevant Pages

  • Re: Building your own flash drive
    ... USB flashdrives? ... If you're "rolling your own" interface and code, compact flash looks just ... SD card readers use an IC that makes the SD card appear, again, as an IDE ... the interface ICs for SD cards or USB memory sticks are ...
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  • Re: Getting photos from USB compactFlash into linux
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