[Soekris] Second Serial Port as RJ45?

Mark Smith mark at halibut.com
Tue Nov 26 22:06:41 UTC 2002

On Tue, Nov 26, 2002 at 10:01:03PM +0100, Bernd Walter wrote:
> > RJ-45 would be a much better choice, if only people followed a single
> > standard.  (Any single standard; even the EIA standard that everyone
> > ignores would be better than each device being different.)
> The problem is that you don't get all wires on an RJ45.

You can get most of what you need.  You can ditch RI and DCD for console
use and you still get hard ware flow control.  The Digiboards (and Boca
Boards) use a 10pin RJ-45 (Is there a special RJ number for 10 pin?)
so you can get RI and DCD.

> But for console I only need 3 wire and all pinouts, that are used today,
> agree on those.

"Agree on" as in "Make available," sure.  As in "have in the same place,"
nope.  Cisco puts GND on 4/5, and TX/RX on 3/6.  Boca/Digiboards reverse
those pairs.  The EIA standard has TX/RX on one side and GND on the other
side; you can't just roll-over a cable to null it.  Of course, you do get
TX and GND on one pair and RX and GND on the other pair, so I guess that
make some sense.

The important part here is that they don't agree, so we'd still need to
get concensus within the Soekris community on which to use.  So far, I've
heard the most support for the Cisco "standard."

> For all other situations there is no real problem to build custom
> cables by need.


> I very much prefer using flat cable (ISDN style) for RJ45 serials.
> It cheap cable and you can easily setup in the exact length you need.
> Exact length is a very fine feature in high density racks.
> And with those cables is easiest to setup such a reversed cable than any
> other pinout.

In small build-out cases, I'd agree with this.  If you have a machine
room built with dozens of cabinets in different rows, possibly in different
rooms, with patch panels running between the cabinets, running your silver
satin may not be feasable.  Then, it's a matter of remembering which of
the patch cables is the roll-over and not using two by accident.

Having said that, I think it is more common for the Soekris board to be
used in a smaller build out, rather than a large machine room, in which
case this discussion goes off topic.  I think we should stick with a
discussion on which RJ-45 standard to suggest to Soren for his boards.

Mark Smith - finger mark at halibut.com for GPG v1.0.1 public key
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