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

Discussion in 'Embedded' started by Michael, Sep 21, 2003.

  1. Michael

    Michael Guest

    Hi - I saw this article:
    http://slashdot.org/articles/03/09/21/1836207.shtml?tid=137&tid=159&tid=186&tid=198
    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?
     
    Michael, Sep 21, 2003
    #1
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  2. and it got me thinking - I mean I've seen people who interfaced AVRs,
    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).
     
    Lewin A.R.W. Edwards, Sep 22, 2003
    #2
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  3. Michael

    Jack Klein Guest

    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
    FAQs for
    comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
    comp.lang.c++ http://www.parashift.com/c++-faq-lite/
    alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq
     
    Jack Klein, Sep 22, 2003
    #3
  4. and it got me thinking - I mean I've seen people who interfaced AVRs,
    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.
     
    Lewin A.R.W. Edwards, Sep 22, 2003
    #4
  5. Michael

    Morris Dovey Guest

    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, Sep 22, 2003
    #5
  6. Only if there's a requirement that a poky 8-bit microcontroller
    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".
     
    Lewin A.R.W. Edwards, Sep 22, 2003
    #6
  7. Michael

    Morris Dovey Guest

    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, Sep 22, 2003
    #7
  8. Michael

    Michael Guest

    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.
     
    Michael, Sep 22, 2003
    #8
  9. Michael

    Michael Guest

    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.
     
    Michael, Sep 22, 2003
    #9
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