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Multiple Display Outputs

Posted on 1998-06-24
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Last Modified: 2010-05-03
Is it possible to direct screen output to a second monitor via a comm port? Seems to me that I saw someone do a powerpoint demo where the presentation was directed to an alternate video display.  The audience didn't see the behind-the-scenes loading and unloading of presentations, just the output.

Can I do the same thing in VB5?  Any tips or hints in coding?

Thanks,
VBert
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Question by:VBert
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Expert Comment

by:Dalin
ID: 1464221
Vbert
I believe the demo you see is from a computer that support an extra monitor. (most notebooks do). I don't think you can do it with a comm port to a monitor.
Regards
Dalin
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Expert Comment

by:Llandr
ID: 1464222
Windows 98 supports this (someway).
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Expert Comment

by:ESI
ID: 1464223
Llandr : Any Window98 API calls welcome !!!
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Expert Comment

by:Dalin
ID: 1464224
Llandr,
Do you mean win98 support an extra monitor by using a comm port?  Then you need a hardware to adapt a comm port ( 9 -pin) to a monitor connect...
It can't be a simpling call APIs...Can it?

 
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Expert Comment

by:michelv
ID: 1464225
Windows '98 supports multiple monitors: You need two have two VGA-cards installed, and then Win98 can use the two vga-cards to display the presentation on one screen, and the loading and stuff you want to do on the other monitor. Driving a monitor from a COM port just can't be done, because:

1. COM-output is very different from VGA-input
2. COM-port speed is too slow (I guess...otherwise all monitors would be driven from cheap COM-ports instead of expensive (talking 'bout the ol' days...:) VGA-cards...)

Greetz, Michel
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Accepted Solution

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selious earned 100 total points
ID: 1464226
Ouch, that's difficult. Indeed, WIndows 98 seems to support multiple videocards (like multiple SCSI cards, it's possible).

But you'll need some assembly or C (assistance)...

If you put two video-cards (sVGA with 1 MB) in your PC, your BIOS searches one, untill he finds one. Than, that one is used (hopefully, but don't be scared when both monitors give an image) by all programs. The other one is somewhere else in your system and can be reached dirrectly from your hardware through I/O ports and that sort of stuff.

From here you must find the VGA specifications (search at assembly sites) and use some PC tool to check out all used IRQ's and that sort of stuff. Now use your manuals to program the card apperently not used.

You need some ActiveX-dll to do the I/O, but they may be availlable.

Very nice idea, cause you'll control the image on the other screen. It would be nice not to use W98 for this, cause than you'll be dealing with windows and stuff (unless you would like so).
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