Re: OT Convert laptop screen to flat monitor?

["Dave McLaughlin" <dave@xxxxxxx>]

Hi Nik,

 

Yes, the digital output that you are referring to is know as Panel Link or DV link and is an LVDS (low voltage differential signalling) standard to transmit the digital signals (quite a few parallel signals of about 18 plus the clocks for an 18 bit panel. 36 bit panels have significantly more connections) on twisted pairs as high speed serial. This allows the signals to be transmitted upto 10-12 metres from the PC. The standard laptop just uses the parallel signals as they are, which can be transmitted upto about 50cm from the source. That is why, if you open a laptop display, there is a big bundle of small cable running from the main board to the LCD.

 

I have not seen many LCD's with the DV links as standard so the price tends to be higher but I guess as supply increases the prices will drop. The interface is indead very much less than converting VGA to LCD signals as can be seen by this link to the Advantech's PCM-3540R LVDS receiver. http://www.advantech.com/products/PCM-3540R.asp

 

I use this in my MP3 player to drive from my SBC and the display is very stable and clear as if I was using the short 50cm lead I originally developed with.

 

Regards

Dave...

----- Original Message -----

From: Nikola Kasic

To: ukha_d@xxxxxxx

Sent: Friday, June 21, 2002 10:20 AM

Subject: RE: [ukha_d] OT Convert laptop screen to flat monitor?

As far as I can remember from some articles, reason is that normal CRT monitors and standalone screens use analogue signal input. VGA signal in PC is converted from digital to analogue, goes on connector and into CRTs. Standalone TFT monitors need digital signal, so every such monitor has D/A convertor, which is expensive and one of the reasons why TFT monitors are still much more expensive than CRT ones.

Because TFT ones are becoming more and more popular and there is no need to convert D/A and back A/D in monitor, some graphic card manufacturers started producing VGA cards with digital outputs, but of course you'll need TFT monitor that can accept that signal. Such monitors should be cheaper, because they don't have A/D convertor, which is expensive.

In laptop VGA cards send digital signals, because TFT screens don't have A/D convertor, because they cannot be detached.

I don't know if digital signal that laptop VGA produces is the same standard as the VGA cards designed for external monitors. Laptop VGA card manufacturers know exactly which TFT monitor will be attached to the card, so they can optimize the card and don't have to follow any standards.

But according to this guy, it seems that it's possible to use such cards.

Those cards can be recognized because they have different connector, with something like + sign. It's a new standard of VGA connectors which has been designed a while ago, and all the monitors should now have such connector (both analogue and digital), but obviously it's not the case yet. Connector is such, so you cannot plug digital monitor in analogue card and vice versa. Monitors that can suport both signals should be able to connect to any card.

Obviously this all didn't work in real life and seems that price of TFT is more conditioned upon market laws than the cost of manufacturing.

That's all I can remember on that topic, when I read about it an year ago.

Cheers,

Nik

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