Re: LCD Dash: Can It Be Done?? [LONG!]

[Vic Watson <vicw@bristol.st.com>]

On Oct 20,  1:52pm, Ewan Marshall - Frans Maas Linlithgow wrote:
> Subject: Re: LCD Dash: Can It Be Done??
> Part of me is saying, yeah sure,no probs,dinny see why not,

This is a fairly common attitude - but once you've been in the trade for a
while, you'll realise that computers do indeed make life easier - for me. It
saves me getting a real job. The rest of you end up paying.

> yet
> every time I look more deeper into it, as to be expected with doing a mod,
> problems and issues arise.

And how!

> Personally,I think it is possible to a LCD
> in there.

Of course it is. You cut the dash out with a jigsaw and epoxy an LCD in. Now
all you have to do is make it useful...

> My original idea was fitting a laptop keyboard (without the
> monitor),linked that to a monitor somewhere in the dash and control things
> like my stereo (which is a fairly good set-up),temps inside and out,but
> basically do nothing.

This application is not real-time, so a PC could do the work. National
Instruments makes a few products that can help - LabWindows/CVI if you're a C
programmer, LabView if you like Visual engineering-style interfaces. I don't
know the costs - I haven't used them for a few years.

> Then I thought about putting a small LCD into
> the Rev counter area,to show info almost in my direct vison,rather than
> take my eyes off the road and look at a monitor.

As soon as you enter the HUD arena, you are looking at plenty more work; it's
not as simple as just plonking a display near the windscreen, because that
changes the focussing distance to your object (pedestrian or display), and it
is the focussing time that dominates the eye's reaction to taking your eyes off
the road. Thus the HUD output must be focussed at infinity to prevent this
refocussing. Watch that project grow...

> Then I remembered
> Solely VW's "16V Nitros Caddy" with a "Digital Dash" from an early
> Vauxhall Astra.

The Astra had an LCD dash some years ago. You may notice that it doesn't now.
Can you guess why?

> As far as I know,these dashes were around in the eighties and are
> legal here in Britain.

They are legal.

> This would be the sort of "speedo" I'd be
> looking for

Which brings us to the next problem - you are now in the realms of real-time
systems. If you are running a conventional PC / Windoze combination to drive
this dash, you will get latency problems (hourglass comes up as you take off
from the lights - how fast are you going?). This is because Windoze is not a
real-time OS. You would need Linux or something like that (if you want a PC
platform - you could use pSOS or VxWorks if you were to use an off-the-shelf
SBC). Unfortunately, the nice graphical interface suites are not available for
Linux, AFAIK.

> which to me, compared to the Astra's 5000 leds,would
> be just as easy,if not easier,to program on an actual LCD screen,

Nope. Bargraph displays are much easier than scanned LCDs. Note also that many
bargraphs don't have the resolution they purport; oftem you will get multiple
LEDs tied together to give the semblance of high resolution, but in fact there
are about a dozen discrete displayable values.

> This
> also tells me that if you can program leds and dot matrix to do
> this,why can't it be done through a LCD?

It _can_. The actual display medium may add complexity, but you can always work
around that. However, the question to be asking is "how appropriate is an LCD
in a vehicle?" You have to deal with vastly different lighting conditions (from
pitch black night driving to direct sunlight onto the front surface). This can
be solved - most fighter aircraft have just such displays for navigation - but
it ain't cheap.

> Mileage could be recorded,

Securely? It's possible (BMW does it), but how good is your cryptography? A
hackable odometer is of no use whatsoever.

> but even if you had to "hide" an analog
> mileometer somewhere in the car

...You'd get a visit from Trading Standards if you ever tried to sell it.

> Everything else in the dash would
> be alot easier

I doubt it. Ever flown? Almost all the instrumentation is in the form of
conventional panel meters, because they're easier to scan. Digital displays
take time to process each one (tom ssee if it's roughly where you want it),
which distracts your attention.

>,as every where I look at my work,water temps,pressures
> and electrical systems are all controlled through workstations.

Think about WHY this is.

> As far as cosmetics ie colours,locations of displays are concerned,
> it's, to me anyway, as simple as adding some open windows type software

Ah. This software is not readily available for real-time system You can't use
Windoze - the speedometer would be considered faulty (due to the latency issues
I discussed earlier), and your car would fail the MOT. Then you can't even
drive it.

I think what we have to remember
> here is that its not the LCD thats doing all the work,

True.

> it's the
> processing,which would be carried out by a laptop type comp which
> is desgined (more or less) for graphical information on a LCD screen,

True - but how are you going to get such a complex system off the ground
without substantial investment of labour or money? You're talking about writing
a GUI essentially from scratch. You could do it - I have - but it's not a
trivial amount of work.

> with the problem being running everything at the same time.It may
> be as simple as adding more processing power and memory (simm) or
> maybe even a high speed CD ROM.

...But it's not. It involves the inherent design of the operating software. And
Windoze is not suitable for RT systems.

> The technology is there to do this and prices are not that bad.I can
> get a 9.4" (Screen size = 260x183x10 lxbxd) Colour F-STN transmissive
> with CFL background lighting,complete with power supply,controler card
> for 450.00 GBPounds ($765.14),only requiring an interface to be purchased.

STN displays are dogs. If you want any kind of clarity (remember this is a
display to be glanced at), you need TFT at the very least. And you haven't
bought a processing unit yet. Or acquisition hardware. Not have you written any
code. The display unit is the very least of your problems.

> Honestly guys, do you really think it will be that difficult

YES.

> or is it
> me thats living in some kind of technology bubble full of great and
> exciting new worlds opening up to us

You've been listening to Uncle Bill again. Remember that his mission in life is
to sell you stuff whether you wanted it or not, and as such is not really a
reliable source of information as to suitability for purpose.

> ......christ could you imagine
> me sending this mail to this list 10 years ago on a computer???

Yes. Computers did exist 10 years ago (and some of us were already making a
living out of them). Email is rather older than you might believe - it has
existed on Unix systems for a very long time.

> I've decided to go for this

I wish you good luck. Really. It's an extravagant project, and I wouldn't do it
for fun, but you will most certainly learn from it.

> and I wanted to explain what I was talking about.My Dad wants me to
> give him a list of everything I would expect this laptop/monitor(s)
> to do and then he's going to go through each part and work out
>
> o Parts list (ie drivers,senders,interfaces etc)
> o Cost - I expect this overall to be expensive
> o Software - What software he would need.

You've missed out the system integration phase; this is the bit that takes all
the (working) components and gets them working together. It is often overlooked
- - and is always essential.

> So I'll let everybody know how things progress and hopefully I'll teach
> the whizz kids out there how out of touch they are! :)

I doubt it. This is my profession & I'm good at it. That's why I earn the cash
I do.

> Do any of you have any ideas on types of software control systems
> that would benefit a Scirocco/car?Let me know!

TCS and ABS.

HTH

Vic.


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| Vic Watson                              SGS-THOMSON Microelectronics |
| Applications Engineer                   1000 Aztec West, Almondsbury |
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