USB Flash Drive to xD

[Mike Warren]

I have started thinking about a hobby project I'd like to do.

I want to create a board to adapt a device that reads and writes xD cards
so it will be able to use USB flash drives.

The plan is to use a small uC and make one end a USB host and the other
pretend to be a xD card, but I have a couple of obstacles to overcome.

1/ I can't find any information on the xD electrical or data spec.
2/ I can't find any information on the current consumption of USB flash
drives.

Does anyone know where I can find out this information? Reverse engineering
it sounds like too much work for this project.

 

[Mike Warren]

I ran into the same problem a couple of years ago.

I'd used smartmedia cards before and, because the xD card has the same
interface, I hoped it would work in a similar way. Cards up to 64 Mb
worked fine but anything larger behaved in an unpredictable way,
sometimes holding its busy pin indefinitely. I eventually gave up and
used a compact flash card.

I found it impossible to find a datasheet. It seems that neither
Olympus nor Fuji will release any useful information.

There are several types. All cards 64MB and lower are 'S' type and
apparently easier to interface with, but it gets more complicated with
the other types. The company that makes the device I want to adapt had
to reverse engineer it because Fuji refused to deal with them, apparently
because they are not a camera manufacturer. Of course, they have problems
with newer cards, which is the main reason I would like to convert it.
All I need to simulate is type 'S'

I'm trying to get information the the device manufacturer at the moment,
but don't like my chances.

 

[Mike Warren]

Can't help much, but I do know the USB power requirements are provided
in the official specifications.
For USB 1.0 devices, I believe the current was limited to 500mA -- but
this upper limit is often adjusted downward after device enumeration.
Note also that for 1.0 devices, not all hardware implementations
enforced these limits.

For 2.0 devices, I "heard" the max allowable current draw was raised
to 1A. Might be 1.1A?
It seems reasonable to assume that the vast majority of USB devices
actually draw less current than is maximally allowed by the relevant
USB standard.

I have no idea about the 3.0 devices. And, can't help you with the
XD spec's at all.
Good luck to you on your project!

I really hope I would not need to supply 500mA. I'm not looking for full
USB host capability, just USB flash drives, and I doubt the small DVD
players I see with USB flash compatibility are able to supply that much
current. I won't need to support USB2 or 3 since the files are small and
the data rate not important.

 

[JosephKK]

I really hope I would not need to supply 500mA. I'm not looking for full
USB host capability, just USB flash drives, and I doubt the small DVD
players I see with USB flash compatibility are able to supply that much
current. I won't need to support USB2 or 3 since the files are small and
the data rate not important.

Won't a $9 adapter do it for you?

 

[Mike Warren]

Won't a $9 adapter do it for you?

I am not wanting to connect an xD card to a computer. I want to connect a
flash drive to a device (music synthesizer) that normally accepts xD cards.

The physical side of this would be easy since the card socket is on a
separate PCB in the synth that is connected to the main PCB by a ribbon
so all I need to do is replace that PCB with my custom one.

The Atmel AT90USB647 looks like a suitable uC, but I'm still lost on the
xD side. The wiki article http://en.wikipedia.org/wiki/XD-Picture_Card
has a link to the Alauda project
http://alauda.sourceforge.net/wikka.php?wakka=XdMedia which in turn has a
couple of promising links, but they are
dead. I also found a pinout: http://pinouts.ru/Memory/xd_card_pinout.shtml