NIC as RS232

NIC as RS232

[Thanasis]

[-- Attachment #1: Type: text/plain, Size: 283 bytes --]

Is there a kernel driver that would make a NIC's port work as a RS232
port, using the serial cables that are RJ45 on one side and DB9 or DB25
on the other? Maybe null modem cables of that type ? Or for example
those used by cisco as console port cables?

(or may be I'm dreaming ;-)

[-- Attachment #2: newerconsolecable.jpg --]
[-- Type: image/jpeg, Size: 21866 bytes --]

Re: NIC as RS232

[Thanasis]

on 01/08/2008 08:48 AM Thanasis wrote the following:
> Is there a kernel driver that would make a NIC's port work as a RS232
> port, using the serial cables that are RJ45 on one side and DB9 or DB25
> on the other? Maybe null modem cables of that type ? Or for example
> those used by cisco as console port cables?
> 
> (or may be I'm dreaming ;-)
> 
> 
> ------------------------------------------------------------------------
> 

Forget my previous question, as I understand now that I gave it a more
serious thought, that it is not a matter of driver, but an
incompatibility between the two in the layer/media carrier level.
(Yea, I was dreaming  :-)

Re: NIC as RS232

[Matti Aarnio]

On Tue, Jan 08, 2008 at 08:48:35AM +0200, Thanasis wrote:
> Is there a kernel driver that would make a NIC's port work as a RS232
> port, using the serial cables that are RJ45 on one side and DB9 or DB25
> on the other? Maybe null modem cables of that type ? Or for example
> those used by cisco as console port cables?
> 
> (or may be I'm dreaming ;-)

With a certain e.g. Freescale embedded communication processors that could
be possible, as those have hardware that can do serial communication in
many different bit patterns, and not being limited only on ethernets.

However even they talk parallel MII protocol to Ethernet PHY, which then
serializes the bitstream for transmit.  Speeds are standard 10 and 100
Mbit/s, and electrical signals depend on wiring standard, probably isolated
differential signals on twisted pairs.

I don't think you can use any ethernet phy hardware for anything but
ethernet frames.  Even when you send bytes over MII, they are still just
a bitstream needing MAC level processing to find correct alignments.

You can, of course, talk ethernet protocol to remote serial port servers,
but these days those systems talk TCP, which makes application programming
all that much easier.


Once upon a time I was talking to a group of telco engineers and said that
"These Telco SDH ports are one of the reasons why bit communication is
expensive.  In the future things will go to optical ethernet interface,
which is either carried over DWM lambdas for long hauls, or just dark
fibers."   Now it looks like I was right..

   /Matti Aarnio

Re: NIC as RS232

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 585 bytes --]

On Tue, 08 Jan 2008 08:48:35 +0200, Thanasis said:

> Is there a kernel driver that would make a NIC's port work as a RS232
> port, using the serial cables that are RJ45 on one side and DB9 or DB25
> on the other? Maybe null modem cables of that type ? Or for example
> those used by cisco as console port cables?
> 
> (or may be I'm dreaming ;-)

What I *have* seen are connectors that go from DB9/25 to RJ11, not RJ45.
Basically, using the RJ11 to terminate a 4-conductor cable wired up for
serial use.  It's often hard to tell an 11 from a 45 unless you look at
it *real* close....

[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]

Re: NIC as RS232

[Geert Uytterhoeven]

On Tue, 8 Jan 2008, Valdis.Kletnieks@vt.edu wrote:
> On Tue, 08 Jan 2008 08:48:35 +0200, Thanasis said:
> > Is there a kernel driver that would make a NIC's port work as a RS232
> > port, using the serial cables that are RJ45 on one side and DB9 or DB25
> > on the other? Maybe null modem cables of that type ? Or for example
> > those used by cisco as console port cables?
> > 
> > (or may be I'm dreaming ;-)
> 
> What I *have* seen are connectors that go from DB9/25 to RJ11, not RJ45.
> Basically, using the RJ11 to terminate a 4-conductor cable wired up for
> serial use.  It's often hard to tell an 11 from a 45 unless you look at
> it *real* close....

We have plenty of DB9-to-RJ45 at work. Very useful when abusing the
Ethernet cabling in the wall for serial connections (also used for
phone).

Maybe surprisingly to you, I haven't seen the RJ11 variant ;-)

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: NIC as RS232

[Jan Engelhardt]

On Jan 9 2008 09:29, Geert Uytterhoeven wrote:
>On Tue, 8 Jan 2008, Valdis.Kletnieks@vt.edu wrote:
>> On Tue, 08 Jan 2008 08:48:35 +0200, Thanasis said:
>> > Is there a kernel driver that would make a NIC's port work as a RS232
>> > port, using the serial cables that are RJ45 on one side and DB9 or DB25
>> > on the other? Maybe null modem cables of that type ? Or for example
>> > those used by cisco as console port cables?
>> > 
>> > (or may be I'm dreaming ;-)
>> 
>> What I *have* seen are connectors that go from DB9/25 to RJ11, not RJ45.
>> Basically, using the RJ11 to terminate a 4-conductor cable wired up for
>> serial use.  It's often hard to tell an 11 from a 45 unless you look at
>> it *real* close....
>
>We have plenty of DB9-to-RJ45 at work. Very useful when abusing the
>Ethernet cabling in the wall for serial connections (also used for
>phone).
>
>Maybe surprisingly to you, I haven't seen the RJ11 variant ;-)

UPSes like APC Back-UPS CS 500 use RJ11/45. Connector has 8 contacts,
but only 4 of them are fed to the to-USB integrated circuit. Funny.

Re: NIC as RS232

[Valdis.Kletnieks]

[-- Attachment #1: Type: text/plain, Size: 627 bytes --]

On Wed, 09 Jan 2008 09:29:41 +0100, Geert Uytterhoeven said:

> We have plenty of DB9-to-RJ45 at work. Very useful when abusing the
> Ethernet cabling in the wall for serial connections (also used for
> phone).
> 
> Maybe surprisingly to you, I haven't seen the RJ11 variant ;-)

I have to admit, the RJ11 variant was from a long time ago, when Ethernet
was still either Thickwire or Thinwire, and this Cat-N stuff was still in
the future, so RJ45 wasn't exactly a common critter.  For reference, the
machine involved was an ATT 3B2-400, and some Blit terminals were in the mix,
which tells you just how far back that was.. ;)

[-- Attachment #2: Type: application/pgp-signature, Size: 226 bytes --]