Re: embedded aviation computers.

["D.F.S." <dfs@xmission.com>]

> > I'm looking at 2 options right now.
> > 
> > I already have, a 266 Mhz "Media GX" system board.
> > 
> > They were a generation of All-in-one mothgerboards that never
> > quite took off.
> > 
> > It can take up to 256 Meg of ram and a has a 266 Mhz pentium clone CPU.
> > I got it about a year ago for $39.00 including the CPU.
> > It has everything on the motherboard.
> > VGA, composite Video, Sound Card, Game port, parallel/serial ports and 
> > a MIDI port. 
> > I can think of several uses for everything but the Midi port.
> > 
> 
> They might never took off because the original price *wasn't* $39.00 ;-)
> Anyway thats good for you and it's probably the hw you wnat to use. I will
> most likely use different hw - unless, of course, that I can get a similar
> deal :-)
My point in posting to simply show this is common as dirt and very cheap.

That $39.00 was not a killer deal or something I, or anyone else here couldn't
go out and match or beat in an hour on the net.

Tis stuff is easy to get, by the same token, a 266 Mhz is a low end system
now, and clearly was a year ago when I bought it, or it wouldn't have been
$39.00.

This was at a local retail store as well.

> People will probably select hw that balance betwenn their economic capability
> and their skills to put it together. Again, the only requirement to the hw
> should be that it is capable of running linux and you can provide drivers for
> whatever devices you might want to utilize. 

Granted, I was just afraid all the custom and embedded talk scared everyone off.
IT was pretty dead here.

I am hardly afraid of the embedded systems, and am looking at some dedicated
subsystems for this project in fact.
The intercom will be all digital, and probably be based on an 8052, or maybe
1742 Pics. 


I just get put off by how overpriced some, no all, of this stuff is.

4-500 bucks for systems based on 3/486 cpus that don't even hold a
candle to the cheap trailing edge all-in-one board I listed above.

There are SOME advantages, but I don't value any of them that much.

> Hmm... aren't you missing something to compute - input from pressure
> transducers, gps, etc. I like the LIAB because it already has pins where you
> can connect various stuff. For an all-in-one computer you would probably need
> some kind of adaptor card - maybe thats not that big a problem, but it all
> adds up.
There are several things I didn't mention because the post was long already, 
and the details were not important to the issues I mentioned.

Part specifics, as a first cut, and in no real order.

Dallas semi. digital Temp sensors -55 - +125 Dec C./-67-257 Deg F.  $3.50 Ea.

TI TLC2543CN, Eleven input  12-bit A/D - $6.50 
(A/D is for Reading analog voltages, stuff like pressures from pressure 
transducers connected to an airspeed indicator air line, a Manifold pressure
line, an oil pressure line, Cyl head and exaust temp sensors, air temp sensors,
electrical system voltages.......)
This one chip will take inputs from eleven such devices.

There are PICs (small self contained Micro controller CPUs) with A/D built in
for under $5.00.

8052 Embedded Microcontrollers, less than a buck.

It would be very possible to plug a module in line with the transponder
and spit the altitude the transponder is sending, out as serial data.
That would require a signoff in all probability.
A seperate atmospheric pressure sensor can be had for $25.00, and would be
a lot more accurate than the 100' increments from the encoder.
 

> Btw what about gps antenna - I've seen that garmin makes one with RS-232
> interface. Does anyone know of something better/cheaper. The big plus of the
> garmin is that you just read the position - no need to mess with almanac and
> translation of codes into coordinates.
Have them.
They do all that and more.
I did mention them, in passing.
They are trimble CM3 variants.
They are smaller than a credit card.
That have 2 serial ports, and will take Diff corrections.
I'll sell them to anyone in the THIS group for $10.00 Ea.
I won't support them, but they work just fine. Trimble support
sucks when you are paying $180.00 Ea, I won't do anything more than 
ship them for ten.
Trimble has a free C interface library to talk to them.
They are a project, and will need a battery for memory backup and
RS-232 Drivers if you need them, along with an antenna.

> 
> Enough about hw - what about the sw. To start with, we need to store the data
> collected (assuming that gps data is easily aquired from the serial port). On
> "big" systems a mysql server could be used, but on systems with limited
> resources something lesser would most likely be better. With that in place,
> we already have a simple logger. 
Along those lines, I have Flash memory modules, they were destined for the
salvage guys, and have an edge of the connector clipped off.
The funny thing is the pins they clipped off are unused :-)!.
They are 8 Meg modules. and about the same size as a Standard SIMM.

This is what I planned to use for the logger mentioned, built with an 8052.
I figured with appropriate storage and compression methods, I could get a
thousand hours on a module before I needed to erase and reuse it.
If I don't download it for that many years of use, I won't care if it's lost
much.

> Next, a user interface is needed - this
> could range from a few buttons and a character display to TFT displays with
> touch screen. The challenge is to build code that is easily adjusted to
> whatever hw you use. 
That would be the issue, we may need to keep some things "Dumb" and draw
a clear line between application and display/input type functions.

If you want other displays rather than standard, default and automaticaly
supported VGA, things change a bit.

You can go all the way from 1-16 LCD displays all the way up to gas plasma
heads-up display units.

And the cost goes all the way from $2.00 to infinity, almost.

> Simply said it could be a core module where you plug modules for you hw into.
> Each module (or driver) is made for one or more (similar) devices. Actually
> something like selecting compile options for a kernel. After selction of
> modules you can customise the setup and off you go.
> 
> Would python be usefull for such project?
I'm afraid once you start getting to the low levels you are talking about,
C is about as high as is reasonable considering the hardware.

Marc
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