Re: [PARPORT] Problem with hardware aquiring port

From: Lucian Daniliuc (
Date: Thu Mar 06 2003 - 04:22:05 EST

  • Next message: Lucian Daniliuc: "Re: [PARPORT] Problem with hardware aquiring port"

    i will try using my old 386 for this hoping that you are right BUT there
    are some items that remain:

    - why can't EXCLUSIVE mode (both in open() and ioctl() ) can't get the
    port to remain 'aquired' ?

    - why under another OS, the port behaves nicely :) ??

    > I too am getting some sort of interference out of the parallel port
    > pins. During my early testing I had installed a test connector to the
    > parallel port with an LED tied to D4 (pin 5). My code should have
    > pulsed the LED on/off at 1Hz (50% duty cycle). Instead, the LED would
    > get short pulses off pulses at 1 Hz.
    > To make matters worse, when I printed to my USB printer, the LED would
    > start blinking oddly even though nothing should have been talking to it.
    > I ran my test in single user mode, uninstalled the printer, tried lots
    > of other things which didn't work. I also ran a test which bypasses the
    > paraport driver and uses ioperm to drive the parallel port. Still no
    > luck.
    > Finally, I ran on an older HP Vectra instead of my e-machine. The HP
    > Vectra did behave nicely, the data pins stayed driven at whatever level
    > I left them for many seconds.
    > I'm guessing that the e-machine i/o chip does something odd when nobody
    > is talking to it. Like after 50ms, it goes back to some default mode.
    > The parallel port does work properly at speed, it just misbehaves
    > inbetween cycles.
    > I'm also new to the parport stuff and could be suffering from excessive
    > user ignorance.
    > --mark


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