[Soekris] serial cabling (was Re: Newbie question)

[Henry Spencer]

On Thu, 29 May 2003, David Kelly wrote:
> > ...I was wondering if it's possible to serial in using a
> > rollover eth cable with 2 serial adapters?
> 
> ...You want to use ethernet cables for a serial connection?

As already noted, no, he doesn't.  It's not at all ridiculous to use Cat5
for serial, however.  It saves stocking yet another flavor of cable, which
is particularly nice if you don't use serial much. 

The one thing you can't do, at least not without losing functionality, is
to use an Ethernet crossover cable as a serial null-modem cable.  The
problem is that a crossover cable only crosses over two of the four pairs.
Even granted the need to have a non-crossover wire for ground, you still
end up with two or three unused wires and a limitation to four signal
lines, which is not always quite enough. 

So you end up stocking two flavors of serial adapters, one straight-through
and one null-modem.  This is annoying but not a big problem, especially if
you color-code them (you can get the adapters in different colors).  Or
else you can just use separate null modems, given that you can now get very
compact ones quite cheap.

                                                          Henry Spencer
                                                       henry at spsystems.net