*BSD News Article 41532


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From: rick@vox.trystero.com (Richard E. Nickle)
Newsgroups: comp.os.386bsd.questions
Subject: Re: How to use lp0?
Date: 24 Jan 1995 01:19:15 GMT
Organization: The Trystero System
Lines: 51
Message-ID: <3g1kij$1sv@sundog.tiac.net>
References: <gsq0fU0@quack.kfu.com>
NNTP-Posting-Host: vox.trystero.com

In article <gsq0fU0@quack.kfu.com>, Nick Sayer <nsayer@quack.kfu.com> wrote:
>I tried hooking two FreeBSD machines up together with a 25 pin straight
>cable, but neither would talk to the other, and both started giving
>'too many errors, downing interface' or some such. What sort of cable
>do you have to make to get this to work (and might someone have done
>well to put this in the man page :-) )?

lp0?  That's a parallel port.  

I thought that the parallel plip thing was going across a laplink cable,
if this is what you're trying to do, this is what you need to get.

I suspect that you're trying to run a serial cable connection between
two machines, in which case, you do not want a straight 25 pin cable,
you want a 'modem eliminator' cable.  These cables have the transmit
on one side hooked up to the receive on the other, and vice versa,
along with various control lines.  Basically they're twisted.  It's
cheaper to go to radio shack and pick up a $5 'null modem' box that
'twists' the signals for you already.

Once you get a null modem cable, you'll be able to run SLIP or PPP
across that line at 115,200 or maybe a little faster (it has to be
a short link for high speed though, signals degrade quickly in 
serial cabling....my experience is that with average cable quality,
you can't get much faster than 57,600 at around 50' or the error
rate goes through the roof [then again, I've put these kinds of systems
into highly RF noisy environments, with not-necessarily so good electrical
power and grounding, so your mileage probably will vary a lot].  
115,200 is probably reasonable on 10'-20' of cable.  Somewhere there's an 
IEEE chart or something that'll tell you what these signal/noise things 
are in various cables.

Alternatively...

It's much more fun to spend $150 and go get two ethernet cards with
dual coax/TP connectors (in case you ever need to hook to one of those
TP stunt boxes), and a bunch of RG58 plenum cable.  If you can find
some junk shop around you that sells used electronics, you can probably
pick up used ethernet cards for $5-$20.

I've done enough serial cabling to last me the rest of my life, thank
you.  Ethernet is *much*, *much* better.






-- 
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Richard Nickle                      http://www.trystero.com/rick.html