From: Jonathan Kirwan
Subject: Re: Urgent help needed to blank monitor
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NNTP-Posting-Date: Mon, 04 Nov 2002 21:45:04 GMT
Organization: AT&T Broadband
Date: Mon, 04 Nov 2002 21:45:04 GMT
On Mon, 4 Nov 2002 19:18:34 -0200, Ulrich Peters
>I wrote a program, which run in a customized PC, using a customized
>keyboard, in a kiosk-like box. The software runs just fine, but now the
>company I wrote that product for, requires that there should be a blank
>monitor while the operating system loads (Windows 2000), and the monitor
>should be turned on only when the application is already running full-
I gather your application is a Win2000 application, then.
>There is no way to do this just with software. Until the software
>starts, shutting down the monitor, the boot process will be shown, so I
>think that the only solution is some electronic circuit which I can
>control with my software.
>My solution I came up with is as follows: I am already able to write a
>certain bit pattern on the parallel port, so I would take four bits of
>that parallel port and feed them into a 74LSxxx to make some digital
>logic, to finally get one logical ON (+5V) if the input bits are set
>Then I would connect that logic high to the gate of two thyristors (or
>should it be triacs?) to make the vertical and horizontal sync signals
>reach the monitor.
>It works like this: I pick the vertical and horizontal sync signals from
>the output of the video port, connect them to the input of the
>thyristors, and when I trigger the gate, the signal becomes available at
>the output pin of the thyristor. From there it will be connected to the
>Without V/H sync, the monitor should stay blank (as it does when the
>energy saver is active). I hope that this way I could control the moment
>I want the monitor to be activated. No more boot process on the screen,
>I would trigger the gate only when my software is already running.
Actually, there may be a way along the lines of the vertical and
horizontal synchs, but not quite as you suggest.
Modern monitors have a 'method' of allowing the graphics board
to signal when to blank the display. There was a standard of
some kind developed over the years, using some special
arrangement on the polarity of the horizontal and vertical sync
signals, if my poor memory serves. Normally illegal states, so
to speak. You allude to this above with your comment on the
'energy saver' mode.
However, Win2000's normal video/monitor drivers will probably
*not* configure things that way for you during its boot up time
or while it starts your application. But on the other hand, it
may still be possible for you to write a small ring 0 tool as
part of the video/monitor driver which will arrange things so
that it happens as you desire. I'm not positive it is possible,
but from what little I know about it, I think its worth a little
If that turns out to be viable, it could avoid the hardware.