7 May
2008
7 May
'08
4:56 p.m.
Subject: Interconnecting classic computers
Quite often I need to transfer data between 2 machines
...
My machines vary in size from the pocket computers
up to machines that it's not practical to move.
They're scattered throughout a house.
They are, alas, not in a machine room.
Most of the machines (and all the ones I want to consider for this)
have an RS232 port, either built-in or as an option (which I have).
Most of the machines run kermit.
Or I can simply print to the RS232 port on one machine
and capture the incoming characters on the other
That's great: that solves the protocol issue and it's all RS232.
So, I think the problem reduces to 'how to
interconnect RS232 ports'.
let me add some constraints :
Must work over a distance longer than the RS232 spec allows
(i.e. the answer is probably not 'A long RS232 cable' :-)).
Prefereably no cables at all.
There are D-I-Y kits for that, and pre-made dongles
for wireless RS232 using bluetooth or Zigbee.
[I got the Circuit Cellar / Freescale Zigbee contest kit
but it failed to flash to the wireless modem program
that I needed for a project]
A "terminal server" puts RS232 ports on ethernet,
but I'm unsure if any have builtin WiFi (802.11)
or are easy to use via WiFi routers/repeaters.
[some are cheap on ebay: I have some but have not
gotten to try them. I used some at a previous assignment].
I saw wireless USB in a catalogue,
so perhaps a wireless USB to a USB-RS232 adapter might work?
I'm suspicious of the USB-RS232 adapters since many are not
8 bit compatible (I learned that the hard way
when one won't download to my PIC-18 development system).
[and most of the USB stuff I've handled lately works under Linux]
One solution I've come up with is to use a couple
of line drivers
and a long cable between them. A long cable that my parents,
or the cat, will get tangled up in :-(
You're just reinvented the "short haul modem":
a dongle that converts RS232 to stronger signals
to travel longer wires, such as RS485 (differential signalling).
BlackBox sells them for $$$:
http://www.blackbox.com/Catalog/Category.aspx?cid=381,1452,1465
That's why I snagged some fiber optic RS232 adapters:
boxes about the size of a pack of cigarettes that converts
RS232 to fiber optic (up to 1 km).
-- Jeffrey Jonas