From owner-freebsd-hackers@FreeBSD.ORG  Mon Dec 18 17:12:37 2006
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
X-Original-To: freebsd-hackers@FreeBSD.ORG
Delivered-To: freebsd-hackers@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id 44C3216A403
	for <freebsd-hackers@FreeBSD.ORG>; Mon, 18 Dec 2006 17:12:37 +0000 (UTC)
	(envelope-from imp@bsdimp.com)
Received: from harmony.bsdimp.com (vc4-2-0-87.dsl.netrack.net [199.45.160.85])
	by mx1.FreeBSD.org (Postfix) with ESMTP id CD56343CB5
	for <freebsd-hackers@FreeBSD.ORG>; Mon, 18 Dec 2006 17:12:36 +0000 (GMT)
	(envelope-from imp@bsdimp.com)
Received: from localhost (localhost [127.0.0.1])
	by harmony.bsdimp.com (8.13.4/8.13.4) with ESMTP id kBIH9tni036276;
	Mon, 18 Dec 2006 10:09:56 -0700 (MST) (envelope-from imp@bsdimp.com)
Date: Mon, 18 Dec 2006 10:10:58 -0700 (MST)
Message-Id: <20061218.101058.1102528461.imp@bsdimp.com>
To: mrcomputerwiz@hotmail.com
From: "M. Warner Losh" <imp@bsdimp.com>
In-Reply-To: <BAY127-F2600E499F0FAE61D967201B3D40@phx.gbl>
References: <200612152025.17442.doconnor@gsoft.com.au>
	<BAY127-F2600E499F0FAE61D967201B3D40@phx.gbl>
X-Mailer: Mew version 4.2 on Emacs 21.3 / Mule 5.0 (SAKAKI)
Mime-Version: 1.0
Content-Type: Text/Plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0
	(harmony.bsdimp.com [127.0.0.1]);
	Mon, 18 Dec 2006 10:09:56 -0700 (MST)
Cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: Capturing Parallel Port Data
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 18 Dec 2006 17:12:37 -0000

In message: <BAY127-F2600E499F0FAE61D967201B3D40@phx.gbl>
            "Mr CW" <mrcomputerwiz@hotmail.com> writes:
: Thank you for the pointers.  It sounds like reading data back from the 
: parallel port is not a common thing to do, although I thought parallel port 
: projects might have done this.  Then I realized that most PIC programmers, 
: parallel port displays, etc. usually only receive data, not send it back to 
: the computer...
: 
: I'm still looking into this, so any other suggestions are very welcome.

I've used parallel port connections in a few different products.

Usually, it is boring DIO stuff.  Not worth mentioning here, and we
use ppi.  However, sometimes we need data.  For that we write a
driver.  We connect the ACK line up as a 'data valid' line and then
read the data and/or control pins when it strobes inside the ISR.  We
use another line to 'ack' the data (which is backwards from how a
printer works).

Warner