From a recent thread posted over at ASSEMbler:
syoyumiso Wrote:Hello!
I can't speak English...sorry.
The method of outputting the screen of NGPC to PC using "Nisetoro capture" is developed.
It is Japanese.
http://blogs.dion.ne.jp/sorairo/archives/10559174.html
What is prepared :
kamereon USBFX2
http://optimize.ath.cx/shopv2_2/chuumon.html
Neogeo Pocket Color(NEW!...Improved version)
Solder
Lead
Resistance
Universal base
2*20 Pin header
2*20 Pin socket
It is not known that I am poor at electronics and it is detailed.
I'm sorry.
However, I would like to introduce.
Behold! the
incredibly accurate Google translation.... 
I think it's the first PCB in the shop link that's required, ¥4980, or about £39.
If you download the .zip file there's a picture of part of the Slim's MoBo, showing the points you need to solder to. There's also some .exe files in there too, but I'm not sure what they're for; unless the USBFX2 board needs flashing?
I've always been interested in pulling an RGB signal from the Pocket, and this seems like the only available solution at the moment.
Yeah, okay, I kinda get it after a while of investigating.
That board seems to be a microcontroller development board. In the ZIP file, he supplies the firmware to flash to the board. I don't think that's what the EXEs are, though, because he mentions using Quartus II in the readme.
The readme also lists the connections to make between the NGPC and the USBFX2. That picture shows which points to solder to on the NGPC. Then you'd need to hook the other end of each wire to the USBFX2.
On his link, there's a video. If you jump to 7:09 in the video, you get the NGPC stuff.
But, I think what is happening is that he's grabbing the NGPC RGB data and shoving it over USB to the PC. Then, there's a PC app that grabs it and just displays it on the screen. Maybe that's what the EXE files are for.
It's a cool technique, but it's not RGB out. However, it's obviously able to grab the data, so maybe the same technique could be used to convert that data to some other video format. I'm no video format expert, but this is interesting data!
There's also
this post over on ASSEMbler, and this is outputting RGB directly into an arcade monitor.
Shou Wrote:It uses an FPGA so it's not straightforward in a sense. Version 2 of the mod will be to consolize it with AES controller ports and map 2 extra buttons that mimic holding the 2 buttons down for a few seconds so fighters are easier to play.
I PM'd him about it, but he's been busy with other things, which is fair enough. I suppose it does at least prove that it is possible to do this using an FPGA.
I've seen the pics from Shou before. I think he uses a different technique for obtaining the video, but I could be wrong about that assumption.
I saw the video and he did it for GBC, NGP and WonderSwan [!!!]. I wonder why he chose those particular games for GBC. One has a tilt sensor, another has the rumble feature. It seems like a fun project, even though I'm missing the point a bit. You might just as well run an emulator on the PC ... Maybe that's why he chose GBC games which come with special hardware and can't be enjoyed the same way on the PC. To show it's real. Same with WonderSwan. He's playing Rhyme Rider Kerorican, which won't give you that sound quality on any emulator [that I know of].