[GreenKeys] Computer to teletype module...

Fri Feb 16 02:25:08 EST 2018

Eric,

Having done my research the past year or so, settled on the design that fit
my needs, and recently built it, here is my opinion for what little value
it brings:

There are two major recent USB<-->TTY designs of which I am aware. There
are likely more, but these are the two that are the best documented thus
far. Neither is superior than the other; both have their uses and were
designed with different approaches. Their creators are on this list and can
speak more to this if they wish. Consider this a customer review of sorts.

The first I came across and the one I ended up building was designed by a
fellow who shares your name, Eric Volpe. The interface is documented here:
http://heepy.net/index.php/USB-teletype While there was a run of these
professionally made on a size-efficient PCB with SMD components around a
couple of years ago I understand, that supply was depleted by the time I
started asking around, so I ended up hand-assembling mine with through-hole
equivalent parts and an Atmel32u2 dev board. This design requires an
external current loop. The firmware written for it is capable of
translating to/from ASCII text for easy piping of data to and from other
applications on the computer. Lastly, the ASCII translation can be turned
off so you instead have raw Baudot coming through your interface to use
with programs like Heavy Metal. There is also a Python set of software
<https://github.com/epvuc/loop-gateway> written by Eric to interface with
various services. I chose this design mainly because its built-in ASCII
translator would give me more flexibility for my plans and because I'd more
easily be able to hand assemble it. Eric was extremely helpful in answering
my questions about the design and certain aspects of some of the components
that I didn't understand.

The second I came across is also a great option, but I'm not nearly as
familiar with it. It is John Nagle's recent design, documented here:
https://github.com/John-Nagle/ttyloopdriver. It's similar in that it's also
a USB/TTY interface, but its "current loop", if you will, is
self-contained, meaning you can connect your machine right up to it without
needing a current loop power supply. It's all powered from USB using a
clever bit of engineering. From what I read on the GitHub readme for this
design, its firmware does not perform ASCII translation (someone-- John or
Steve-- correct me if this is wrong), but there is, of course, software
that already exists like Heavy Metal that makes this easier to deal with.
John also wrote baudotrss <https://github.com/John-Nagle/baudotrss>, which
looks like it parses RSS feeds as well as sends/receives SMS. While you
could probably find through-hole equivalents for the components used in
this design, it's been designed strictly with SMD components. SMT is beyond
my skill, nor do I wish to invest in the hardware that's really needed to
do it right. It's definitely a good thing to learn if you want to truly get
into modern electronics, though. This was the one main factor in why I
decided not to use this design.

Either of the above designs could be professionally manufactured if hand
soldering and figuring out through-hole equivalent components is not your
thing. The problem I've found with this is that it requires a relatively
large run to make the price per unit palatable, and I don't know that there
is enough interest to have a large enough run done. Still, it's getting
cheaper all the time to manufacture custom boards (and it's super cheap to
have custom PCBs made). I would definitely put my name down for one or two
of each of these designs should someone organize a movement to have them
manufactured.

On a related note, there is, of course, iTelex. While not a USB option, you
could connect to it over your network (or across the internet, for that
matter) with your Mac using simple tools like telnet or netcat (install
homebrew <https://brew.sh/> to get either easily) to send/receive text.
It's a worthy project that I intend to join in time. The boards are already
manufactured for you by our friends in Germany, include a current loop
(there may be a requirement of an external power supply for the loop-- I
forget, but I think that was the case; there are other US members who would
be more than happy to point you to a good external supply), and I believe
they are around $200 US if I recall correctly.

There are definitely other methods of connecting modern computers to their
distant teletype ancestors, but these I think are the easiest and currently
have the best support in my experience and research.

--Jordan

On Thu, Feb 15, 2018 at 10:15 PM, E. <hanyou at xsmail.com> wrote:

>
> Hey,
>
> I know over the past couple of years, there has been quite a bit of
> discussion here about the best computer to teletype converter boards
> made/available to make/designed out there.  Has there been a consensus yet
> on what is the best or have there been any new, recent designs?  I’m
> looking at trying to hook up my Mac up to my Model 19 (yes, Mac)… to give
> it a try at least… so curious as to what others think is top notch.
> Planning on my permanent wiring scheme before committing to buy the stuff.
>
> Thanks!
>
> Sincerely,
> Eric
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