Using an X Windows Terminal as an RS232 debug interface

howy wrote:

> Back in the late 1980's to early 1990's when Unix work stations
> transitionsed from text-based to graphical interfaces (at least thats
> when I saw it happening in college), I was under the impression that
> the graphical user interface was based on a stream of ASCII commands
> similar to PostScript. 

I guess those were actually TEK terminal graphics command streams or 
similar.

But serious confusion of terms is reigning here.  There are various 
different things called "terminals".  So I guess it's time for a little 
excursion to history.

First, there were relatively dumb keyboard+screen devices that served as 
mere human interfaces devices to a central multi-user computer, 
typically on a point-to-point serial line.  Since they were at the 
endpoint of a long-ish cable, it was only fitting that they ended up 
being called "terminals".  The canonical example is DEC's VT100.  Some 
of these terminals were enhanced with graphical vector-drawing 
capabilities as a separate mode of operation (e.g. the TEK4010).  I've 
never seen it done, but some people certainly must have used this to 
implement early GUIs, although it poses quite an amount of stress on the 
host computer.

Then came the next major step: The X Window System, a.k.a. X11.  The key 
differences are that more intelligence was shifted to the terminal end 
of the chain to reduce load on the host, and the point-to-point 
connection was replaced by general-purpose networking.  Thus the "X 
terminal" was born: a special-purpose user-interface computer running 
the "X Server".  X11-enabled "client" programs can be started on any 
computer and have their user interface on any X server on the network. 
The X terminal also implements protocols to start such client sessions 
on remote machines.  When you hear buzzwords like "thin client" or 
"network computer", it helps to think "X Terminal"

Gradually the roles of X terminal and "main computer" merged, and the 
result was the Unix/X11 workstation, most of which these days are Linux PCs.

Now, just about the most important X11 client programs is XTerm, the "X 
Windows Terminal emulator".  Now hold on to your hat for the explanation 
of what it does: XTerm emulates an old-style dumb terminal in an X11 
window to show up on an X Terminal.  In other words, it's a virtual 
VT100 that runs on a "real" computer, and provides the user interface to 
a command-line program inside a window.  In particular, it's not an 
emulator of an X terminal, but a terminal emulator that is an X client.

And then of course there's the kind of "terminal program" you're really 
looking for: a serial communications program.  That's the kind of 
program you would run to connect to a RS232 device and display its 
output.  The canonical one used to be Kermit, with minicom a close second.

howy wrote:

>>You're probably thinking of Display Postscript, not X.
>>Still, it sounds like you need something more like syslog than X or..
> 
> 
> OK, thanks I will look into that.
> 
> I was hoping there was a standard terminal emulator protocol (like a
> graphical version of a VT100 terminal) that would allow me to place a
> few buttons, graphs, and text windows on the PC's screen and maybe
> even accept user input commands like button press events and keyboard
> input - over a low bitrate serial stream.
> 

I use AT&T's FMLI (the source is now available in OpenSolaris) on a
variety of projects to build curses-based GUIs -- graphs are only
possible using characters from the extended set but it would do what
you suggest.  I have a demo "ascii oscilloscope" program written
in C for the i8096 on my site and also a GUI running on the 'zipit'
based on FMLI if your interested.

Regards,

Michael

OK, I guess was some what mis-informed from the beginning.  I asked
the original question half assuming someone would say, "sure you can
do it that way, but here is the way every one else is doing it...".

I remember seeing an ad for a LCD touch screen that had a GUI
scripting language built into it. Maybe I will see if they are still
in business. Otherwise I might have to roll my own (or pay someone
else to do it for me).

Thanks for you help everyone,
-howy

In article <1187716636.149447.211110@g4g2000hsf.googlegroups.com>, howy 
says...
> OK, I guess was some what mis-informed from the beginning.  I asked
> the original question half assuming someone would say, "sure you can
> do it that way, but here is the way every one else is doing it...".
> 
> I remember seeing an ad for a LCD touch screen that had a GUI
> scripting language built into it. Maybe I will see if they are still
> in business. Otherwise I might have to roll my own (or pay someone
> else to do it for me).

Are you thinking of Amulet?

http://www.amulettechnologies.com/products/products.html

Robert

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