Re: [PARPORT] PPSETMODE and the control lines in EPP

From: Tim Waugh (
Date: Tue Dec 12 2000 - 05:12:21 EST

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    On Mon, Dec 11, 2000 at 05:40:38PM -0800, Crump, Valerie wrote:

    > epp=IEEE1284_MODE_EPP;
    > ioctl(fd,PPSETMODE,&mode)
    > doesn't change the control lines from compatability mode to EPP mode

    No, SETMODE just tells ppdev what to do on read/write, it doesn't
    touch the port at all.

    > transfers. Subsequent read and write calls do not cause any activity on
    > the control lines.

    That's bad, but probably caused by the control lines not being set
    right. You need to put them in a known state really if you're using

    > I think it may have something to do with the direction bit, but I
    > thought that was handled automatically in the hardware. If I alternate
    > EPP mode writes and reads (no two or more of either in a row), the data
    > lines are set and read correctly. But there's no address or data
    > strobing. The second write or read does not set or read the data lines
    > correctly.

    This sounds like bugs somewhere. To find out where you need to know
    which code path is being used: software (ieee1284_ops.c) or hardware


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