Ritter said:
Is there a way to use the HP laptop screen with a HP desktop?
I want to test a monitor at a friend whose computer (also HP) seems
going off after a while, yet graphics card is fine, power source not
hoy, monitor not hot, all cables new. And he has no other monitor to
test it with.
A laptop screen uses a "private" rather than a "public"
interface. The laptop cable is intended to work with the
laptop main body, and the cable is likely to only work
well if the cable is kept pretty short.
To use a laptop screen, you'd have to find a part number on it,
download the datasheet, see what data format it uses, and try
and convince the driving device to put out that format. And
that isn't likely to happen.
This is an example of an LCD panel, so you can understand
that it is a "raw" device, and needs some knowledge about
electronics to use it. It looks to me like the interface
is similar to DVI (serial interface, diff pair per R,G,B plus
a clock) but it looks like vanilla LVDS serial, rather than being a
transition minimized format.
http://www.datasheetcatalog.org/datasheet/nec/NL10276BC28-05D.pdf
TMDS is what might come out of a DVI connector. There is a
10 bit value on each of the R,G,B signals. It must be
decoded to give a "raw" 8 bit value. So you need a decoding
stage. In the case of the above sample LCD panel, the panel is
a 6 bit type, so two of the bits must be throw away or
otherwise provided for (dithering? dunno how you drive a
6 bit panel). And the data is in a high speed serial format
on the panel as well. So this takes a handful of electronics,
to convert from DVI/TMDS to something that little panel can use.
http://en.wikipedia.org/wiki/TMDS
On a computer monitor, you'll find a printed circuit board
with adaptation chips, fastened to the back of a raw panel.
In the case of the laptop screen, that adaptation circuit
is missing. The GPU is convinced to put out the necessary
data pattern on say, an SDVO output interface (parallel bus?).
Maybe there is another little driver chip, such as an
LVDS transmitter (a parallel to serial converter), to
finish the job.
The GPU in the laptop, might use a concept equivalent
to the SIL164. I don't think this is still in production,
but what it does, is parallel to serial conversion, for
driving a panel. The high speed serial on this is not
transition minimized, and the output cable stays
short.
http://web.archive.org/web/20021023004158/www.siimage.com/documents/SiI-DS-0021-A.PDF
Sounds like a fun project if you can find the chips, own
a soldering iron etc etc.
If the laptop display had a "public" interface, followed
an accepted standard, then it would be more useful for
what you want to do. Such a device is also known as
a desktop LCD monitor.
Paul
