Paul:

     Reading all your posts on EFI systems and GPS intefacing has kept me
     thinking about what might be the best operating system to use if one
     wanted to create an entire home-brewed glass-panel display.

     I ran the idea past my wife's cousin, who is now retired from a
    position
     as a programmer for some Silicon Valley hardware developer.  He
     suggested a look at TCL (pronouced: Tickle)


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An update here on my Home-Brewed Glass Panel generated in Tcl scripts.
It has been a steep learning curve for me.  I have found references to
Tcl methods used on Androids, so I think my efforts might prove to be
worthwhile.

Most of the TCL manuals and tutorials are written for much different
purposes, and they are obviously written by people who created the
language modules in the first place, so they've left a LOT of basic
stuff unexplained that I've had to figure our by searching the web for
examples. (For example, it took me an entire day to figure out how to
make a display-screen continuously update, and it required just one word
of code).

So I now have a reasonable looking screen that is continuously updated
by routines that simulate the reading of data from a computer port. I
use a loop-counter and pass the current loop-count to trig functions
that create pseudo-engine operating parameters and flight conditions. I
have created these routines for the Tach, AirSpeed, Attitude, Altimeter,
Compass, and Oil Pressure. I can either display moving arrow(s) on a
dial, vertical (or horizontal) bar graphs, or a rotating dial (as
illustrated by the compass). The rotating compass rose requires a
different image for each heading, 360 images if one desires one-degree
resolution, so it will be quite time consuming to generate all of them.
Each image needs to be created/rotated in a very large size and high
resolution, then reduced down to panel-size to create clear images. Each
compass-rose image I created is about 11K in size, so making a pretty
system does suck up a bit a memory as well.

To run the GlassPanel Tcl script one can set up a machine using a number
of methods:  (1) Install the Tcl developer/run-time on the machine, then
run the GlassPanel program in the same way that the developer does.
(2) Use one of several "wrapper" programs available that combines all
scripts/images/interpreters/etc into one big executable program.  In
theory that should work for any machine.  I tried two or three of these
wrapper utilities and got it to work on one Linux machine. When I tried
to get the software to run as a wrapped-package on another Linux
machine, I got a "segmentation" error, so I do not know what the problem
is there. I had the most success with a wrapper-program called Starkit,
which combines with Tclkit to create a standalone application.  I also
worked with a wrapper program call Freewrap, which was easy to use but I
could not get it to work with all the GlassPanel images; it didn't like
the steam-gauges.

So now I think I could use some help ...  Does anyone know of a
inexpensive (ie Free) board of some sort that I could plug into my USB
port that might feed me a data-stream?  I thought I could use my
Earthmate GPS but my GPS chip-set doesnt communicate well with my
verison of Linux; it locks up.  I could probably hang another computer
on the USB cable and program it to spit out a data stream, but I do not
want to take the time to do that.

The following screenshot is a snapshot of an active screen.  The needles
move around,  the aircraft soars over the artificial horizon,  the
oil-pressure creeps up/down, and the compass-rose rotates (at only
5-degree precision so far)


R Berglund

The AVR Xplain is $30 bucks but you will have to program it in asm or C.

Paul Lamar