modding IDE cable to write-protect compact flash?

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hi all:

I am involved in a mini-project that is to build a solid state computer
(mini-ITX based) that will feature read-only medium. we have chosen
compact flash for its relatively cheap cost and larger compacity. and due
to the phyiscal limitations of the setup, we cannot use the popular
USB-flash sticks that come with a write-protect switch, we have to stick
with a CompactFlash-to-IDE converter.

it would be really nice if we could somehow protect the data on the
Compact Flash on a physical layer. we have thought about mounting the
Compact Flash read-only, but that doesn't protect the data on the Compact
Flash to be modified if someone gained super-user access to this machine.

i am wondering if it is feasible to short a few pins in the standard IDE
cable, so that the write signal does not get passed onto the Compact Flash
card. has anyone attempted similar solutions? i would really appreciate
any pointers and suggestions.

Thanks in advance.

Re: modding IDE cable to write-protect compact flash?
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A similar idea is on our drawing board.  One of our client wants to be
able to control both reading and writing to the CF.  Our solution is
to gate the addresses and read/write enable lines with a CPLD
sequencer.  Unfortunately, the added board space (more than 2.5" x
1.5") makes it unattractive for other clients.  For now, this version
is going to this one client only, as part of the agreement as well.

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Most of them can't boot from USB, period.

...

IDE-CF Compact Flash Drive
http://ide-cf.info-for.us

Re: modding IDE cable to write-protect compact flash?
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indeed, we have a certain space to play with, and unfortunatly, someone in
the group has already gone as far as getting a bunch of custom cases made,
and because he has already spent all that money and time into it, we
didn't want to throw those cases away. and due to the design and space of
these custom cases, it's impossible for us to go with anything USB
based... the CF card slot will be in the front of the case, looking muhc
more like a floppy drive.



Re: modding IDE cable to write-protect compact flash?
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Back to the orginal issue, the USB CF write protection is implemented
on the USB controller chip.  You need some simple logic to map the
data port and read/write signals, a simple CPLD would do it.  We might
end up with another small board with two IDE connectors and a mach211
(just because we have a whole bunch of them).

Re: modding IDE cable to write-protect compact flash?

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Ah!  Now I see.  You *want* a larger solution.  Yes, CompactFlash will
provide that.

BTW, at the Dayton Computerfest today I noticed an adapter that went from
a USB header to four or six kinds of flash memory card slots mounted in a
floppy disk-sized enclosure.  It was only $10, but I couldn't come up with
enough motivation to get it (while carrying out loads of rack-mount stuff).

--kyler

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