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I'm interested in the prospect of using a RP to run MAME in a real arcade cabinet.

The easy way is to replace the cabinet's monitor. However I'd really like the authenticity of keeping the original 15Khz RGB monitor.

Does anyone have any suggestions as to how one could drive such a monitor from a RP?

Edit: On standard PC hardware, this is a pretty well understood area. Some graphics cards can be underclocked to 15Hz. Get one of these cards, get suitable drivers, and use something like AdvMAME. The challenge with RP is that it hasn't an interface these graphics cards could use.

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Very intersting mod. I found this.. mmmonkey.co.uk/console/other/rgb2vga.htm I have no idea what is going on but maybe it will help you? Has the monitor got video in ? ntsc/pal/ scart or something? and this? youtube.com/watch?v=W1MfqbyGamE –  ppumkin Jul 31 '12 at 16:03
    
Thanks ppumkin. The first link is conversion in the wrong direction: upscaling a lo-res input to VGA. The second link is the right kind of thing. Is there a way to hook an RPi to a PCI/AGP/whatever video card? –  slim Jul 31 '12 at 16:11
    
I don't think you will get close to handling PCI or AGP im a afraid. Maybe ISA but you will have to do some mega driver code and software will be rubbish. Try and keep looking for CGA to VGA hardware solutions. Just need to reverse the process. –  ppumkin Jul 31 '12 at 16:16
    
If the 15 KHz monitor uses television timings, I would think you could use the pi's composite output, with a composite to RGB/Sync converter circuit, if the monitor doesn't already have that - though of course composite will not be as sharp due to the limited color bandwidth. What would be ideal would be some sort of HDMI-to-SCART device. –  Chris Stratton Jul 31 '12 at 17:30
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I did this for my old arcade machine but with a PC of course. wire mapping was pretty easy. AdvMAME is really good for setting video output to 15Khz as well and easy to get set up in linux. Wish I could provide some more info. Good luck! –  Bryan Aug 3 '12 at 5:23
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1 Answer

Firstly, since the Raspberry Pi doesn't have an RGB out, you will need an ACTIVE (with a chip to logically convert Digital to Analog) HDMI to VGA. I use one of these on my RPi and it works great- for older VGA monitors.. but yet again the price is going up...

enter image description here

I bought this HDMI to VGA from ebay

  • I have Model B, I do not know if it will work on Model A because of power constraints.
  • Also you have to read this. Apparently using and inline active converter can cause long term issues with out tweaking something on the board....
  • UPDATE: In revision C boards and older the power constraint is no longer an issue

So you can get this one suggested by Mark Booth if you are concerned about the issues described in the wiki.


Secondly, you will need to convert from VGA to CGA. Something like this bad boy! (known as a GBS-8100)

enter image description here

You can buy it on ebay for not that cheap.. But maybe it can help you develop some other mod along the same line?


Some additional references that might help you with alternative home brew solutions.

This looks like a converter but not sure if it actually does anything in processing the signal to the correct format.

Again another way to take CGA into Scart.. but maybe some reverse can be applied?

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This is unlikely to help, as the pi does not have VGA output. –  Chris Stratton Jul 31 '12 at 17:27
    
With that kind of attitude - No its not going to help anybody.. I edited my answer- because I forgot I use a DVI to VGA thinga ma doo daa. Problem solved. not cheap though –  ppumkin Jul 31 '12 at 17:41
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@Mark no, the basic technical issue remains in thst it is unclear if results would be satisfactory after the additional conversion. More importantly, after the cost of two converters is added, most of the advantages of a raspberry pi vs other low cost (or recycled) platforms are negated. –  Chris Stratton Aug 1 '12 at 11:45
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@ChrisStratton - That's an entirely different argument. We have no idea if slim is constrained by cost or just wants to do this for the fun if it. This answer does now address your original concern, anything else is beyond the scope of this question. Feel free to post a better answer, if you have one. –  Mark Booth Aug 1 '12 at 11:57
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@Slim you are correct in both your assumptions. To get Composite you need RGB - But its done using hardware inside the BCM chip- so you cannot hook it in any level of software. If there was VGA output, or VGA pin outs it would make life allot easier for some people –  ppumkin Aug 3 '12 at 14:00
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