OT: Ethernet extender

A bit OT for the group, but it is related to an embedded system ...

I have an application that requires Ethernet to be extended through an 
existing RS485 serial link, such that I have Ethernet <-> RS485 <-> Ethernet.

I'm aware that there are any number of copper wire Ethernet extenders that
will work on bare copper, but unfortunately I have the serial link in
the path so I can't get to the bare copper at all.

I also know that there are any number of Ethernet->Serial conversion
boxes, but they all seem to be one-path units for converting something
that was serial I/O to sit on a LAN.  Neither of these things is what
I want.

Is there anything I can buy to complete the link?  I'm not quite sure what
I should be looking for or asking Google for!  I know I could build 
something to do what we need, but I'd rather not if possible.


Robert

> A bit OT for the group, but it is related to an embedded system ...
> 
> I have an application that requires Ethernet to be extended through an 
> existing RS485 serial link, such that I have Ethernet <-> RS485 <-> Ethernet.
> 
> I'm aware that there are any number of copper wire Ethernet extenders that
> will work on bare copper, but unfortunately I have the serial link in
> the path so I can't get to the bare copper at all.
> 
> I also know that there are any number of Ethernet->Serial conversion
> boxes, but they all seem to be one-path units for converting something
> that was serial I/O to sit on a LAN.  Neither of these things is what
> I want.
> 
> Is there anything I can buy to complete the link?  I'm not quite sure what
> I should be looking for or asking Google for!  I know I could build 
> something to do what we need, but I'd rather not if possible.

You want a pair of RS232<>Ethernet bridges such as this 
<http://www.dcbnet.com/datasheet/etherbridge.html> (first Google hit). 
This is, of course, provided that you have the sole use of the RS485 
link.  If not you will have to write the equivalent.  You will probably 
want to filter multicast and broadcast traffic going over the link.

	Andrew

> You want a pair of RS232<>Ethernet bridges such as this 

I meant, of course, RS485<>Ethernet bridge! (Sigh: end of day)

	Andrew

Andrew Jackson <alj@nospam.com> wrote:
>> You want a pair of RS232<>Ethernet bridges such as this 
>
> I meant, of course, RS485<>Ethernet bridge! (Sigh: end of day)

Fantastic Andrew, thanks for that - the thing that was confounding me
was "bridge" - stupidly didn't think of that term, once I got "extender"
in my mind nothing else came.  Searching for Ethernet serial bridge finds
lots of similar things.

Regards,
Robert

Robert Anderson wrote:
> Andrew Jackson <alj@nospam.com> wrote:
>>> You want a pair of RS232<>Ethernet bridges such as this 
>> I meant, of course, RS485<>Ethernet bridge! (Sigh: end of day)
> 
> Fantastic Andrew, thanks for that - the thing that was confounding me
> was "bridge" - stupidly didn't think of that term, once I got "extender"
> in my mind nothing else came.  Searching for Ethernet serial bridge finds
> lots of similar things.

If you have exclusive use of the RS485 wire then why not remove the 
RS485 transceivers in favor of the more common and faster "ethernet 
extenders"?

Recently had need to temporarily link two locations 5,000' apart with 
ethernet interfaces on each end. IIRC a pair of COTS boxes were $400 and 
served nicely. Basically they were private line DSL modems talking to 
each other over a single twisted pair.

David Kelly <n4hhe@Yahoo.com> wrote:
> Robert Anderson wrote:
>> Andrew Jackson <alj@nospam.com> wrote:
>>>> You want a pair of RS232<>Ethernet bridges such as this 
>>> I meant, of course, RS485<>Ethernet bridge! (Sigh: end of day)
>> 
>> Fantastic Andrew, thanks for that - the thing that was confounding me
>> was "bridge" - stupidly didn't think of that term, once I got "extender"
>> in my mind nothing else came.  Searching for Ethernet serial bridge finds
>> lots of similar things.
>
> If you have exclusive use of the RS485 wire then why not remove the 
> RS485 transceivers in favor of the more common and faster "ethernet 
> extenders"?

Unfortunately we only have exclusive use of the line in the sense that
"nothing else is using it", not that we can rip out the existing
hardware.  Actually, there are two possibilities, one with serial
tranceivers and one with bare wire, depending on various other things.  
Obviously we'd prefer bare wire, but ours isn't to reason why ... :-)

> Recently had need to temporarily link two locations 5,000' apart with 
> ethernet interfaces on each end. IIRC a pair of COTS boxes were $400 and 
> served nicely. Basically they were private line DSL modems talking to 
> each other over a single twisted pair.

Yep, that would be the preferred case.

Robert