[GreenKeys] Model 33 ethernet connectivity

[gil smith]

Hi Chris:

I'd like to know more about your plans to use SitePlayer.  I have used a 
couple of ethernet-to-serial modules (xport and cas) in products, but never 
tried using something like that for a tty.  It makes a lot of sense 
though.  I had considered using one to front-end my tty-connect board -- I 
could then telnet to it and send a stream of data to either the (ascii) 
low-volt loop for an M33/35..., or the (baudot) high-volt loop for an 
M14/15/28...  The ascii-to-baudot conversion is already done on the board.

It sounds like you only want to connect to a 33, so the baudot conversion 
goes away.  And you can use a pretty simple low-voltage 232-to-20mA circuit 
to drive the M33.

As you found, the 2-stop bit thing can be important so characters are not 
lost during M33 printing -- if the siteplayer folks are going to implement 
2-stops, that is great.  Their stuff is pretty cheap too.   You could 
insert inter-character delays at a higher level, but 2-stops is the clean 
way to go.

The other thing to keep in mind is insertion of nulls after CR, so the 
carriage goes fully back to the left.  This can be done in your application 
program, and you could even count the number of characters on the current 
line and send just the right number of nulls to compensate.  Or, maybe the 
siteplayer folks would add a programmable (but fixed) number of optional 
post-CR nulls for you.

It would be nice to make two little gizmo 
modules:  ethernet-to-ascii-20mA-loop (a low-volt loop for M33s), and an 
ethernet-to-baudot-60mA-loop (high-volt loop for other stuff).  If these 
could be made cheap enough, you could have one at each tty (or local loop 
of ttys) and just plug in an ethernet cable.  Or even make it wireless 
ethernet.

That would solve the hardware connectivity issue, but at this point all you 
can do with existing software is to open a telnet session to the 
appropriate ip address and port number, and manually type to the tty.  Plus 
you need to be able to configure the ethernet module for a static address, 
or look in your router's table to find the dynamically-assigned dhcp ip 
address.

Now if you can write custom software, you can do more, by opening a tcp/ip 
socket connection to the same address/port numbers and get application 
access to the serial-port/current-loop.  But what do you do now?  You could 
connect to different machines, or patch different loops of machines 
together via software, etc.  You still have the issue with the ip address, 
which you can work around with static addressing, but unless your ethernet 
module provides some method of discovery, you can't automatically find a 
dynamic address in your software program.

It would also be nice if Bill Buzbee's heavymetal program could be modified 
to talk to an ethernet tty (Bill?).  All the great functionality he has in 
there for email, weather, and other cool stuff, could just get piped to a 
tcp socket in pure ascii form, getting around the whole 5-bit serial port 
problem.  Baudot conversion just moves to the ethernet/loop adapter, and 
data throttling is handled over ethernet, much like how I use xon/xoff to 
throttle 232 ascii data into tty-connect.

MY WISH LIST:  I plug my M33 into an ethernet-to-LV gizmo, plug my M15 into 
an ethernet-to-baudot-converting-HV gizmo, plug my TU into a 232 or loop 
gizmo.  A program running on a pc finds them all as they come online, and 
lets me send filtered email summaries to one tty, news and weather 
headlines to another tty, TU traffic to another...  Oh, and automatic motor 
powering for each tty as well.  And the gizmos need to stay cool.

Sounds feasible enough, and I kinda started down that path with stuff I 
did, but the final result still eludes me.  The software in the center is 
key, and I have no interest in writing pc code.  Embedded C keeps me busy 
enough.

Let me know what you find, as I am quite interested in where you are 
headed.  Maybe we can work together on it somewhat if you'd like -- I can 
do circuit boards, and interfacing microcontrollers, if you can get the 
high-end software to work.

gil


At 03:20 PM 6/3/2008, you wrote:
>OK. Will do.  The mission is to "ethernet enable" the tty33 with a
>single port terminal server.  The SitePlayer Telnet module I am using
>(http://www.siteplayer.com/telnet/index.html) did not support 2 stop
>bits so I am working with the firmware developers to add that capability
>and ensuring that we have the proper bits/character as well.
>
>These little terminal servers emulate Smart Modems with an AT command
>set.  So, when we are done, you will be able to type on the tty,
>
>         ATDT{some_ip_number}    eg, ATDT192.168.1.9
>
>and a telnet connection will be made from the tty to any host on your
>network or the Internet in general.  I will use this to connect the
>tty to various vintage computers I have on my network also connected to
>other terminal servers.
>
>So, we're slamming the old and the new together here hoping for some
>excitement :-)
>
>73, Chris N0JCF
>
>--
>Chris Elmquist
>mailto:chrise at pobox.com
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>GreenKeys mailing list
>GreenKeys at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/greenkeys



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