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USB to parallel

Discussion in 'Electronic Design' started by Marco Trapanese, May 14, 2009.

  1. Hi to all,

    I'm looking for a chip to use a virtual parallel port through an USB
    connection. For example FTDI makes FT232* ICs for RS232 serial ports. I
    need something like that but for parallel ports.

    Of course, third parts applications should run fine either with physical
    or virtual parallel ports.

    May you point out me any chip?

    Thanks
    Marco
     
  2. Rich Webb

    Rich Webb Guest

    A legacy application (not a simple parallel printer) that assumed that
    it was interfaced to a genuine hardware parallel port at 0x378 will
    almost certainly not work with a USB connection in the middle. Things
    like parallel port based device programmers don't translate well to an
    intermediate packet based layer.

    It might be possible to come up with a way to fool a particular
    application into running over a USB-parallel port. Designing an adapter
    that supported all third party applications (which will include some
    that were written back in the days of MS-DOS and 5 1/4" floppies) is ...
    challenging.
     
  3. Rich Webb ha scritto:


    Ok, thank you very much for your answer. Furthermore, the main
    application should be a stepper motor driver: I bet the USB device can't
    handle the clock rate as accurate as the hardware parallel port can.

    Marco
     
  4. What part of a USB port is not hardware? Also, one could easily write
    the stepper motor app and design the I/O interface such that no
    difference could be detected.
     
  5. Archimedes' Lever ha scritto:

    I'm talking about the USB protocol.


    Of course. But I need to interface existing apps.

    Marco
     
  6. FTDI also make FT245* devices that have a parallel interface (no, it's
    not exactly equivalent to a PC parallel port (IEEE 1284) but it does give
    you the ability to bit-bash several I/O lines). Their newer devices,
    e.g. FT2232D, can be run in a number of modes, allowing them to emulate
    both the '245 and the '232 parts.

    The very newest FTDI parts, e.g. FT2232H, use USB2.0 which might allay
    some of your timing concerns.

    Regards,
    Allan
     
  7. Rich Webb

    Rich Webb Guest

    For a given application it may be possible to implement a USB solution,
    particularly if you're comfortable with sticking a microcontroller "in
    the middle" to handle the low-level timing issues. That still may not
    fly if the host application on the PC side expects to have well-defined
    command/response cycles on the I/O lines.

    An option may be to try a PCMCIA parallel port. These could be (note:
    not all are) identical to a legacy hardware port. Or an expansion card,
    if you're running a desktop or PC/104 unit.
     
  8. Rich Webb ha scritto:

    Thank you again.
    Marco
     
  9. Jasen Betts

    Jasen Betts Guest

    if you can put the USB in isochronous mode it will do it better than a
    hardware parallel port can.
     
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