[GreenKeys] RS232 to TTY Loop

[epvgk at limpoc.com]

On Sat, Feb 19, 2011 at 10:27:09AM -0500, Wa3frp wrote:
> 
> 
> Hi guys, 
> 
> I was wondering if anyone has a solution for me.  
> I am looking to key my 60 ma teleprinter loop from my laptop using the RS-232 interface. 
> I see that Gil had a solution about ten years ago (no longer available) called tty232.  
> Is there anything else available? 


I was sort of considering doing a device like this, along the same sort of
lines as the AFSK demodulator boards I did recently, though it sounds like 
there are already a couple of options available. 

My thoughts were maybe something with a builtin ASCII/baudot conversion and 
speed shifting and buffering so you could send, say 300 baud ASCII, and have 
Baudot come out at a configurable speed, to key the loop. Naturally the sender
would need to support flow control, but that seems to be achievable with
windows and linux at least. 

We could also have it be bidirectional so you could get data from the loop
as well as sending out. Handling half duplex communications on an OS that
expects full duplex is a bit of a pain, and I'll happily leave that part to
others, though. :) 

If it's going to have logic for buffering and code conversion and a USB 
interface it may be a bit more expensive than the RTTY demodulators just 
because it will probably need to be a surface-mount design with two-sided
board and solder paste stencil, etc. but it should still be reasonable. 

Anyway, I by no means want to usurp anyone else's projects or anything like
that, I just thought I'd throw out the idea to see if it sounded interesting
or useful.  On the other hand, it seems like most everyone connecting a 
computer to a teletype loop these days is using HeavyMetal or the like, which 
already handle the code conversion and 5 bit formatting and data rate for you,
so maybe a simple hardware passthrough would be enough? 

eric


> 
> Thanks and 73 Russ WA3FRP
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