[PARPORT] parport undetermined under linux

From: Dörte Lache (doerte_lache@web.de)
Date: Fri Jul 05 2002 - 18:31:41 EDT

  • Next message: Robert Heller: "[PARPORT] *Simple* Parallel port I/O..."

    Dear group!

    My parrallel port runs very odd under linux. It behaves undetermined.
    The next thing sounds funny, but it's no joke:
    There seems to be a connection to hard disk accesses: The more hd accesses,
    the more "activity" I get on the parport. This is espescially valid for the data bits
    of the port. The odd activity starts, as soon as I boot linux. Under windows,
    the lines are just set to high. And calm! I have an eprom burner to the port connected,
    which works under windows. That's why I think, my parrallel port is all right.
    (Even though I connected -12V of of my computers power suply to GND of the parport
    some days ago) I am sure, that no other process runs on the port. I tried for example
    at init level 1. Maybe linux does not support my parport correctly? On the other hand,
    it's not that I don't have any control at all to the port. If I do s.th. like
    while (1) outb(0x01,0x378); it will run. But with spikes. I tried my code on a different
    machine and on that machine everything worked as expected. No spikes and no
    unpredictable behavior. I could write and read from my eprom burner board
    as expected.
    Any idea? I don't have any experience with the parport, this is my first project I
    am dealing with it. I don't even know exactly, what kind of hardware the parrallel port
    is. Please do not hesitate to write me all of your comments, even if it's trivial for you.

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