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Discuss modifications you have done or plan to do to your Dreamcast or any other hardware, or discuss devices you want to build. If your console does not work or is acting up, ask about fixing it in here.
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I've got a new mission for all of you Hardware experts!

Post by MidnightObsidian » Wed Dec 31, 1969 6:00 pm

I'd love to see someone find a way to turn a modem attachment into a VGA adaptor. I have a modem and a VGA box, but I would love to find a way to cram that entire thing (along with the dreamcast) into that single compact package.

If anyone has any ideas, please let me know. I'm not sure if it'd be possible to stream the video data over the peripheral bus or if you would have to run wires from the video connector over... but I'd love to give it a shot. >= )

So please let me know. IM me at MidnightObsidian or e-mail me at ObsidianInfern0@aol.com
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Post by BobsShadow » Wed Dec 31, 1969 6:00 pm

I don't really think this would be possible since the modem takes up most of the space inside the case for it. People have however put a modem inside a Dreamcast. I think Marvin did this so maybe you should ask him. I'm not sure if if he has a website or not but if he does there might be pictures on his site. You should also know how to build a VGA box yourself. I think that i@n made a homemade one a while back.
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Post by I@N » Wed Dec 31, 1969 6:00 pm

Yeah, I made a homemade VGA adaptor for the DC and it works a treat. The circuitboard is tiny so it will easily fit inside the DCs case (but it is a bit fiddly).

I have lost the scematics I had for the adaptor :(, but if you are really interested in making one I will try to draw them out again.
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Post by MidnightObsidian » Wed Dec 31, 1969 6:00 pm

I@N, if it wouldn't be too difficult, I would love to get my hands on those instructions. Is it possible to carry the video data over the peripheral bus? That way I could make the thing completely detachable... just as if it were a modem or a BBA. I'm not sure if what I'm asking is even feasable... so please don't laugh at me if I'm just dreaming.

As to ShadowOfBob, I'm not sure you understood me completely. I don't want or need my modem-- I was hoping to just use the ready-made plastic packaging for my VGA Adaptor, just so it wouldn't be external. >= ) Sorry if I said it incorrectly.

--MidnightObsidian
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Post by I@N » Wed Dec 31, 1969 6:00 pm

OK, I will try and do something over the weekend (but alas I am quite lazy ;)).

I don't think it will be possible to make the vga adaptor detatchable in the way that you want (unless you want to make serious and possibly fatal modifications to the DC's motherboard). It is simply a small PCB that connects to a 15 way high density D-type connector (monitor connector) that is mounted on the rear of the console.

If these forums had an upload feature still it would be much easier to explain this with a picture.
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Post by MidnightObsidian » Wed Dec 31, 1969 6:00 pm

Thank you SO much...
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Post by TheDumbAss » Wed Dec 31, 1969 6:00 pm

An idea would be to do I@N's method... then put that PCboard inside the modem case. Then to make the modem detachable run a cable to a custom plug (from radioshack or a broken electronic device maybe) and build half the plug into the Dreamcast near the parellel port. The other half the plug would be built into the modem case and aligned so that it connects to the part of the plug in the dreamcast case.

Somewhat incoherant... (Bed time). But maybe you get what Im saying.
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Post by I@N » Wed Dec 31, 1969 6:00 pm

Sorry, due to unforseen circumstances I was busy over the weekend, but I will try to do the modded schematic tomorrow (it is quite simple).

Anyway, here is the unmodded circuit so at least you can see what components you will need (the only modification needed is with the switch).

http://www.gamesx.com/grafx/dricas.gif

Obviously you do not need to use the composite, or S-video connectors if you don't need them.

I hope this helps :)
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Post by LithJoe » Wed Dec 31, 1969 6:00 pm

i have the circuit diagram i drew for the vgabox based on i@n's original post, if anyone wants it, just email me at lithjoe@hotmail.com, it has a simple vero board layout too.

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Post by I@N » Wed Dec 31, 1969 6:00 pm

Well here it is:

http://www.geocities.com/imhill/dcvga.htm (do not click on any of the adverts on that site though)

As the diagram states, if you are making an internal VGA adaptor, you will (probably) need a DPDT switch with a Centre-off position, this is important as otherwise it could cause problems if/when you try to plug a standard video lead into the console to connect it to a TV. If you are simply making a detatchable external version (that plugs into the AV port) you can simplify the circuit to use a cheaper SPST switch.

If making a detachable external version you will need an appropriate connector to plug into the DC. The only way to get one is to buy an RGB/SCART lead for the DC (last time I looked, Lik-Sang were selling them very chaply), simply cut off the connector & open it up (I think Tom61 has recently posted details of how to do this in another thread), then solder wires from it to the circuit you have made.

You may also want to add a stereo line out socket so you can connect your PC speakers, or hi-fi to the console.

Finally, if making an internal version you will need to dismantle your console & solder the wired directly on to the rear of the AV socket. This is very fiddly, so if you are unsure of your abilities then do not attempt it. Please do not blame me if you damage your console.

Just remembered, I should probably explain what the switch does;

When it is in the centre position, neither the VGA, nor RGB pins are at 0v, this means other video connectors can be used without problems.

When both VGA & RGB pins are at 0v, the DC outputs a standard VGA signal, this only works on games designed for the VGA box.

For games that otherwise do not support the VGA box, you must start the console with only the RGB pin at 0v, there will be no display on the monitor, so you need to guesstumate when the Sega License screen disappears, at which point wsitch it into VGA mode, the game should play properly from then on (although there are a small number of games that will not work with the VGA box :()

If you have any further questions then just ask & I will do my best to answer them :)
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Post by I@N » Wed Dec 31, 1969 6:00 pm

Update:

In an attempt to clear up some possible confusion, I added a photo of the VGA lead I built to the previous link.

I hope this helps :)
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Post by timefun » Thu Nov 29, 2001 5:45 am

I@N, i like the diagram... lots of help for me..

do you think is there posibility of input an AV Video signal through the vga box and display it on monitor..

i would like very much to play my saturn on the monitor through dc vga box.
like at lik-sang they have Av video to minitor adapter (cost a lot).


but the AV video only has two signals.. + & - (correct me)
the monitor needs red,blue,green to out put the video.

can some verify this..
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Post by I@N » Thu Nov 29, 2001 12:54 pm

Timefun wrote;

do you think is there posibility of input an AV Video signal through the vga box and display it on monitor..
There is a long and complex answer to this, but basically the answer is no, it cannot be done (without expensive and overly complex circuitry).

You can buy ICs that split composite video into seperate RGB & Sync outputs, but alas there is a more fundemental problem.

Normal TVs need a video sync running at 15KHz, whereas PC monitors need a video sync running at 31KHz (I am not 100% sure about the exact values stated here, but you get the idea).

There is no easy way to convert the 15KHz output from normal consoles to the 31KHz needed for monitors. I think the items sold by Lik-Sang & the like somehow digitise each frame and output a VGA signal. However, I have heard that many of the cheaper units ($500 or lower) severly degrade the picture, and as the point of playing on a VGA monitor is to get a superior picture they seem quite pointless :(

If you really want to play a Saturn on a VGA monitor, then I would suggest you get a gfx card for your PC that has video capture inputs.

Just in case you were wondering how the DC can work on a VGA monitor, when both of the RGB & VGA pins on the AV connector are at 0v then the sync pulses outputted change from the standard 15KHz to the required 31KHz.

I thought this was going to be the quick answer :roll:

Anyway, I hope this helps :)
Drink your weak lemon drink now!
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thanks

Post by timefun » Fri Nov 30, 2001 8:23 am

that's cool I@N.. i was just wondering that's all.
yeah i was thinking of a video card but after saw that diagram i thought you might know how to find a way too..
but thanks
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Post by MidnightObsidian » Sat Dec 01, 2001 12:20 am

Thank you so, so, so, so much, I@N. I owe you, BIGTIME.

--Eddie
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Post by O.P.G-RAMIN » Sat Dec 01, 2001 2:38 am

Will this vga also make the graphics smoot end lookin g good like you will get woth a vga box for the sega cas i wana make it but i wana b sure i will get mutch smooter graphics :D
P.s thx for the shematic man it rulzz :D
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Post by I@N » Sat Dec 01, 2001 5:50 am

Yes it does make the DC's graphics much better in exactly the same way a commercially available vga box does.

I hope this helps :)
Drink your weak lemon drink now!
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Post by Wilykat » Sun Dec 02, 2001 12:38 pm

Just wondering what is the 74HT244? Is this some kind of counter circuit? I'm asking because my local Radio Shack didn't have it.
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Post by I@N » Sun Dec 02, 2001 2:35 pm

The 74HC244 IC is an Octal Buffer circuit. You could also try any 74244 chip (74LS244, 74HCT244 etc).

You could also try a 74HC241 IC which I am 90% sure would work just as well (but please don't blame me if it doesn't).

I hope this helps :)
Drink your weak lemon drink now!
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Post by Wilykat » Sun Dec 02, 2001 3:22 pm

Ah thanks. Hmmm been a while since I've heard the term octal. Isn't that also called base8, or 3 bit binary digits?
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