how hard would it be to create a external hard drive enclosure?

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Hi - I saw this article:
http://slashdot.org/articles/03/09/21/1836207.shtml?tid13%7&tid15%9&tid18%6&tid19%8
and it got me thinking - I mean I've seen people who interfaced AVRs,
PICs and various other uCs to IDE hard drives - and certainly you can
add usb and ethernet connectivity to any of these uCs - so how hard
and expensive would it be to create a hard drive enclosure like this?
Say - maybe one with ethernet, usb 2.0, and firewire connectivity?
Seems like it could be done pretty cheaply - and a whole lot cheaper
than the file server from that /. article (that one actually has a
mini atx board in it. Could this be done very easily and cheaply?

Re: how hard would it be to create a external hard drive enclosure?
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It's not difficult, but it has low performance. Using a PC motherboard gives
you [perhaps multiple] 100bT or gigabit Ethernet connections, and UDMA66 or
faster transfers to/from the hard drive, plus a nontrivial amount of disk
cache (main memory in the PC).




Re: how hard would it be to create a external hard drive enclosure?
On 21 Sep 2003 15:12:36 -0700, snipped-for-privacy@hotmail.com (Michael) wrote in
comp.arch.embedded:

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http://slashdot.org/articles/03/09/21/1836207.shtml?tid13%7&tid15%9&tid18%6&tid19%8
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Despite another reply that you have gotten, it can be done and done
well.  Not too long ago I purchased an external drive made by Western
Digital for back up.  It is a slick plastic enclosure with a 120 GB
drive, with both USB 2.0 and firewire interfaces, no Ethernet.

I haven't opened it up to see what kind of processor is inside, but
the speed is impressive, not slow at all.

--
Jack Klein
Home: http://JK-Technology.Com
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Re: how hard would it be to create a external hard drive enclosure?
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An utterly different, non-comparable scenario. For one thing, the OP is
talking about a device that includes Ethernet. That means either he has to
write custom software on the PC end, or he has to implement a filesystem and
an FTP or SMB (or NFS or ...) sharepoint inside the device. This means that
ALL the data, and some interpretive work, has to be funneled through the
microcontroller. Further, he's talking about micros that do not have inbuilt
hardware support for DMAing to/from IDE and/or 1394/USB interfaces. So even
if he just wanted to build a dumb 1394/USB->IDE interface, it would be far
slower than the kinds of devices you're talking about.

The AVRs and PICs mentioned are an order of magnitude too slow do do all
this bit-banging. Purpose-built interfaces use ASICs. The HDD DMAs into a
buffer, the 1394 or USB interface DMAs out of the buffer; the micro issues
start and stop commands, basically. This is a totally different scenario
from trying to squeeze all the data through a poky 8-bit microcontroller.

To do it properly would be difficult and a lot of work.




Re: how hard would it be to create a external hard drive enclosure?

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Only if there's a requirement that a poky 8-bit microcontroller
be used. I've used MIPS chips from Philips that would handle this
job easily. (Rummages in drawer and squints to read: PTD1100).
You'd need to add external PHY, and a Flash for software; but
it'd all fit on a 2" x 3" PCB.
--
Morris Dovey
West Des Moines, Iowa USA
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Re: how hard would it be to create a external hard drive enclosure?
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And MIPS would be part of the "PIC or AVR" families since ... when? The OP
was specifically asking about these toy projects. Yes, you can do it with a
32-bit microcontroller. This qualifies as "difficult".



Re: how hard would it be to create a external hard drive enclosure?

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Hmm. I would have put MIPS in the "various other" catagory. The
particular chip I mentioned already has USB and Ethernet MAC,
plenty of on-board RAM, particularly nice DMA architecture, and
an intelligent external bus interface. (There are also EJTAG and
UART I/F to make development easier).

The only aspect that looks difficult is the soldering :-)

Sorry - somehow I missed the "toy" stipulation. I think if I were
going to build something like this (even just a one-off for
myself), I'd go for all the performance and reliability I could
afford...
--
Morris Dovey
West Des Moines, Iowa USA
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Re: how hard would it be to create a external hard drive enclosure?
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Yes pics and avrs are the only ucs I mentioned by name - but only
because they are the ones that are familiar to me. I'd be open to any
suggestions.

Re: how hard would it be to create a external hard drive enclosure?
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So I looked up this chip - and it seemed to be some part of a cable
modem (pdf here:
http://www.semiconductors.philips.com/acrobat/literature/9397/75007613.pdf )
So are you sure this is the right chip? This is starting to sound like
a fun project to mess around with for a while. An open source very
well connected external hard drive anyone? What do you think? And what
exactly is a PHY? I googled and kept on finding links to PHYsics
stuff.

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