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How do USB-IDE cables work?

Discussion in 'Electronic Design' started by [email protected], Nov 9, 2007.

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  1. Guest

    So I've got one of these USB-IDE cables. Plug in a spare IDE drive
    into the cable, plug in the other end into a computer's USB slot, and
    the drive gets recognized. Usually without even needing software
    drivers.

    How does this work, though?

    Is it straight-through wiring? Or is there a chip hiding somewhere on
    the IDE plug?

    Reason I'm asking - should I worry about data integrity when
    transferring data? I could make a tarball out of my files when
    performing backups, and perform a sha1sum on this, but if data
    integrity are already assured, these are needless, time-consuming
    steps...

    Any input, from experts in the field?

    Thanks,

    Michael R. Darrett, P.E.
     
  2. Joel Koltner

    Joel Koltner Guest

    There's a chip with a pretty fancy set of digital logic in it.
    Probably not. USB sends CRCs along with all of its data transfers, so it's
    pretty unlikely that your PC won't notice if the data does become corrupted
    somewhere inbetween the hard drive and the PC itself.
     
  3. Joerg

    Joerg Guest

    The better breed of USB devices has the necessary drivers and stuff
    right on there. The not so good ones still require you to plop in an
    install CD. For example the Logitech wireless mouse was true
    plug-and-play. No CD needed, plug in, a few mouse clicks, done. The
    digital camera, a whole 'nother story. Refuses to download onto a newer
    PC (so far).

    There can be some weirdnesses though: For example when zip files are
    stored on my LAN drive and I want to unzip them right there and into the
    same directory I receive the error message "Not a ZIP File". If I copy
    that very file to a local HD it unzips just fine. Ok, that LAN drive
    runs Linux but I still don't understand why because the unzip routine
    runs on a Windows PC.
     
  4. donald

    donald Guest

    Must be a windows user.
    Isn't it amazing that a P.E. did not notice that the USB plug has 4 pins
    and a IDE interface has 40 pins.

    Or is there a chip hiding somewhere on
    And we have another gmail loser.

    donald
     
  5. Frank Buss

    Frank Buss Guest

    This would be a good Dilbert story :)

    customer: My USB device doesn't work.
    support: Just plug-in the device and copy the drivers.
    customer: But I can't do this, because my USB device is not working!
    support: I see. Looks like you didn't read the fine print: You need to buy
    an extra computer to copy the drivers!
     
  6. Guest


    Actually, I don't recall my Fedora Core installation requesting
    drivers either.


    I'd thought, perhaps the USB sent the data serially using fewer pins.

    I'm a chemical engineer PE, not an Electrical PE. Are you an
    Electrical PE?


    It works, for free, on whatever machine I use. So I use it.

    Thanks to everyone else for the... more useful... replies

    Michael R. Darrett, P.E.
     
  7. Nobody

    Nobody Guest

    And the worse breed of operating systems will just load the drivers
    automatically.

    This guy discovered that people will happily plug in USB flash drives
    found lying on the ground outside the office:

    http://www.darkreading.com/document.asp?doc_id=95556&WT.svl=column1_1

    Now, programs run from a flash drive will normally only get the privileges
    of the user who runs them. But if you can provide your own driver, that
    will run with kernel privileges.
     
  8. Joel Koltner

    Joel Koltner Guest

    Sure, although in Windows XP "regular" users can't install drivers anyway.
    There's also a registry key that controls whether any unsigned driver will
    automatically (silently) install (not a good idea!), prompt the user to choose
    whether to install it or not (the default), or completely refuse to isntall
    it.

    Not that I'm suggesting plugging in a "found" USB memory stick is a good idea.

    For a well-funded operation (commercial or national espionage) it wouldn't be
    difficult at all to go to a store, buy a bunch of memory sticks, plant your
    trojans on them, re-package them and return to the store to put them back on
    the shelf ("unstealing"). Hmm...
     
  9. Chemical engineering P.E.?

    Ok, consider a manifold with 4 pipes on one side and 40 on the other.
    Your task is to get all 40 streams from one side through the 4 pipes
    on the other side without cross-contamination.
     
  10. Guest


    Wow, look at this. 25 pins in, two pins out. And it WORKS! It's
    magic, I tell you.

    http://www.taomc.com/bits2bots/litbit.htm

    Michael R. Darrett, P.E.
     
  11. IIRC, there are a few standard USB device classes, such as mouse,
    keyboard and mass storage. As long as the device identifies itself as
    one of these types, the OS standard drivers should work with it. No
    additional drivers need to be installed.

    Digital cameras (for the most part) are _not_ mass storage devices and
    do not work with the standard USB device class drivers. They require
    custom drivers to be installed.
    That may be due to how the Linux system maps FAT/VFAT file names from
    the LAN drive (an SMB device, I assume). There are many weirdnesses in
    how Linux/Samba handle file names and permissions. Check out the Samba
    man pages to see all the screwball options. From what I've heard,
    Microsoft has developed quite a few nearly incompatible versions of SMB
    in the past. Due to personnel turnover and a lack of documentation, the
    only decent resource for understanding how they all fit together are the
    people working on the Samba project.
     

  12. Every digital camera I ever plugged into any PC I ever plugged one into
    saw it as a removable storage media device and assigned it a volume
    letter in windows or Linux. In fact, I can even plug one into my PSP.
     
  13. A volume letter in Linux? Never seen one.

    While there probably are some cheap cameras that provide a mass storage
    interface on a USB port, most of the higher end models that I've seen
    have remote control capabilities that don't map to block device I/O.
    Aside from that detail, many newer Linux distributions include Gphoto,
    which supports loadable driver modules for quite a few higher end
    cameras. These drivers provide support for viewing the camera's contents
    as a mountable file system as well as supporting other functions.

    Try lsmod before and after plugging in a camera to see which drivers are
    loaded.
     
  14. whit3rd

    whit3rd Guest

    Hey, that's NOT the important part. It's possible to play an
    ExpressCard through four of its many pins, because those four
    ARE a USB2 interface. It isn't possible for IDE and USB
    mainly because of interface-age-and-paradigm differences
    that are completely invisible from outside.

    USB requires intelligence and uses negotiation to determine
    device type, address, etc. IDE requires a classic I/O bus
    of the type in an IBM PC/AT (with lotsa speed and other
    enhancements added in as an afterthought). Thus, IDE devices
    are generally not programmable for USB functions. The USB/IDE
    adapter has a smart interface for the USB bus, which makes
    negotiation claims appropriate to a generic 'mass storage class'
    driver model and handles data transfers through USB,
    and another (dumb, relatively) IDE interface handled
    according to some IDE protocol (not necessarily a full
    functioned DMA133 capability, it could be VERY limited).

    The USB/IDE interface has to be a small computer with two
    standard computer interfaces and maybe an activity LED.
     
  15. JosephKK

    JosephKK Guest

    whit3rd posted to sci.electronics.design:
    Nahh. Even a relatively small FPGA can do it easily.
     
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