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Re: Heads up display
The TTL to instruments could be J1850 VPW obd2 or obd1
Alex
----- Original Message -----
From: Dan Gentry <dang@seanet.com>
To: <gmecm@diy-efi.org>
Sent: Friday, May 26, 2000 9:10 AM
Subject: Re: Heads up display
> Um, whoops. See below.
>
> Peter Gargano wrote:
>
> > Did you have a message hidden somewhere within the ">" quotes?
>
> Dave Hempstead wrote:
>
> > Hi Dan,
> > Well I can tell you what I know about HUD's and PCM's. In your 95
> > Z28, your PCM has software in it for a HUD. It collects lots of data
> > from its sensors, and sends it to some HUD hardware.
>
>
> Right. I don't know if it's a question of having HUD-specific software in
the ECM or
> not though.
>
>
> > Now, never having seen the HUD or the hardware driving it, I can't
> > tell you how to hook it up, but it sounds like you have some ideas
> > there.
>
> Yup - I've been lucky enough to find two "friendly" auto dealers here in
the Seattle
> area that were kind enough to let me leaf through service manuals and get
photocopies of
> some
> rather important data.
>
>
> > Also, I BELIEVE that you may need to set a bit or two inside the
PCM
> > to enable the HUD. I'm not sure here, because I haven't studied the
HUD
> > code in that much detail (usually I just skip right past it), but I'm
> > not sure if it is always enabled, or if it is enabled by plugging in
the
> > HUD hardware.
>
> Oooh, I didn't know that. Interesting.
>
>
> > Having said all of this, I am now wondering if we are talking about
> > the same HUD's or not. It is my understanding that the 94/95 PCM's
> > drive a HUD for GM's test purposes. However, maybe the HUD is one and
> > the same.
>
> > Maybe you can enlighten us on what HUD's you know about, and what
> > they are available on.
>
>
> Okay - here goes.
>
> I know for sure that 1999 & 2000 Corvettes and (at least) 1994->2000 Grand
Prix models
> have the Heads-Up Display as an option.
>
> I'm casually aware, but not sure in any detail that other GM models have
HUDs (Olds,
> Buick, etc).
>
> GM's HUDs are made by Delco Electronics (naturally!), and have the trade
name of
> "Eye-Cue".
>
> GM Vehicles equipped with HUDs have a special windshield that is a
sandwich of different
> materials to make the HUD image clearer. I'm assuming that the special
quality of the
> material (referred to as PVB in Delco's literature) is some kind of
polarizing filter.
>
> The HUD units that I've been able to read about in service manuals are
single enclosed
> units with display, optics, and adjustment motors enclosed in a neat and
tidy package.
>
> I do not know if there is enough space behind a Camaro dash to install a
Vette or GP
> HUD. Some mods would certainly be required.
>
> The part number of the HUD on 1994-1996 Grand Prix models is 16141842.
HUDs from this
> era that are defective are sent to a third party (Instrument Sales and
Service here in
> Seattle, and others across the country). They will not sell a HUD without
an defective
> exchange. (Darn!)
>
> The GP HUD shows Speed, Turn Signals, and other idiot lights. It gets
speed data from
> the PCM at the rate of 4000 pulses per mile. The PCM gets it's data from
the Vehicle
> Speed
> Sensor. The manual states that the output of the VSS is a sine wave.
I'm assuming
> that once the analog output of the VSS hits the computer it gets converted
to something
> a little
> more TTL. The output from there goes to the instrument cluster. BTW:
Does anyone know
> the specifics of this signal so I don't have to go buy an o-scope to
figure it out?!
>
> The 'Vette HUD seems to be a much more advanced unit. The Vette service
manuals don't
> have nearly the same level of wiring detail as early books do - I'm
assuming that there
> is a
> computer program that displays detailed diagrams in the repair bay. The
HUD unit itself
> costs $992 (as quoted by the Chevy dealer) - OUCH! The wiring harness for
the HUD
> looked
> like it plugged into the back of the speedo cluster, but I can't tell.
>
> There is a Japanese company (http://www.defi-shop.com) that sells an
add-on HUD which
> uses a polarized window film and sits on top of the dash. I was going to
purchase one,
> but the information states (in the docs on the site) that the input speed
pulse must be
> 2, 4, 6, 8, or 16 pulses per mile.
>
> Knowing that my Camaro (along with Grand Prix and Vettes) puts out 4000
pulses per mile,
> I didn't order it.
>
> There - now you know as much as I do about the subject. Not much, is it?!
>
> Here's how I'm thinking about proceeding:
>
> 1: Try to develop a circuit ( Basic Stamp?) that will divide the VSS pulse
by 1000 and
> purchase the Japanese HUD.
> 2: Try to develop a whole HUD myself (again, Basic Stamp). Use the VSS
and Tach inputs.
>
> 3: Continue to pursue the option of finding a "used" HUD from a Junkyard.
(No luck so
> far.)
> 4: Use an in-car computer (my MP3 player) to talk to the ALDL and get the
data from
> there, driving a display.
>
>
> What do you think?
>
> Dan
>
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