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Neo Geo Pocket Color Video Out (DAC/FPGA)

kragit

Hi everyone!

 

Looking to achieve RGB analog video out on a Neo Geo Pocket Color. No known mods currently exist for this. There are single digit K2_VIDEOs out in the wild that achieve this, but I believe these were made by SNK themselves for internal use only. Other people have apparently gotten video out with FPGAs, but no one has publicly documented it.

 

Here are the LCD signals as printed on the board & additional information from someone who's apparently achieved this:

 

I've done it with a small FPGA. The LCD signals can't be simpler: R0~3 is 4bit red, G0~3 is 4bit green, B0~3 is 4bit blue, DOTCLK is the pixel clock, SPL is horizontal sync, SPS is frame sync.
[...]
It can't be done by just wiring a scart cable to the board, you have to buffer and convert the color data from the NGPC, then do digital to analog conversion if you want analog RGB output.

 

I'm venturing into the FPGA scene for this with no past experience with FPGAs and a rudimentary understanding of digital electronics (I can follow guides, solder, etc. I built a CMVS this way).

 

Any help would be appreciated. Thanks!

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  • 0

    These are general comments about FPGAs and VGA output and probably not all that helpful for the NPGC, but here goes anyway.

     

    There are a number of FPGA boards out there that support VGA graphics, and some have tutorials available.  Gadget Factory's Papilio boards are very nice and have a VGA "wing".  It's not clear whether it's 8 or 64 colors.  The older through-hole version has 8 colors, but the photo of the SMT version at the link has enough resistors to do 64.  They both use resistors to make a "poor man's" DAC, which can probably get you up to 4 bits per color.  There's sample code around to generate VGA output -- I think it's VHDL.  (I like Verilog better.)

     

    The LOGI-PI and LOGI-Bone boards have a pretty powerful FPGA and you can get a LOGI-Edu adapter with VGA output (512 colors, I think).  The boards can be used stand-alone but you need an external programmer.

     

    Another nifty board is the Nandland Go Board, which has built-in VGA.  The FPGA on that board is pretty small, but it has the advantage that you can use open-source tools instead of the far more complex vendor tools.  The Go Board doesn't have much RAM -- just the small amount in the FPGA itself -- so it's probably no good for your NPGC project.

     

    I don't know what availability is these days for these boards.  I haven't done VGA output myself.  I plan to one of these days, since I have all those boards.  Just need more time!

     

    Hope this helps and/or inspires.

  • 0 in reply to johnbeetem

    Appreciate the info! The biggest thing is just trying to figure out where to start as a total beginner.

  • 0 in reply to kragit

    Adam Kragt wrote:

     

    Appreciate the info! The biggest thing is just trying to figure out where to start as a total beginner.

    With FPGAs, start by copying a tutorial design exactly.  FPGA tools have a steep learning curve -- "The Cliffs of Insanity" is how I put it.  By copying a tutorial exactly you reduce the dozens of things that can go wrong down to something more reasonable.  Once you have something working, you can modify it to produce the design you really want.

     

    With the exception of Lattice iCE40, FPGA internal bit stream formats are undocumented which means that there have been very few open-source tools developed despite the interest of many people in doing so.  You're mostly much stuck with "free-as-in-beer" vendor tools.  Here's one of my periodic screeds on the subject: Taming the Wild Bitstream

     

    A really good way to get started is to download the free vendor tools and try them out.  I mostly use Xilinx, but a lot of people prefer Altera.  You can then make sure you can work through tutorials and produce bitstreams and see if this is going to be something you're interested in before even buying a development board.

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  • 0 in reply to kragit

    Adam Kragt wrote:

     

    Appreciate the info! The biggest thing is just trying to figure out where to start as a total beginner.

    With FPGAs, start by copying a tutorial design exactly.  FPGA tools have a steep learning curve -- "The Cliffs of Insanity" is how I put it.  By copying a tutorial exactly you reduce the dozens of things that can go wrong down to something more reasonable.  Once you have something working, you can modify it to produce the design you really want.

     

    With the exception of Lattice iCE40, FPGA internal bit stream formats are undocumented which means that there have been very few open-source tools developed despite the interest of many people in doing so.  You're mostly much stuck with "free-as-in-beer" vendor tools.  Here's one of my periodic screeds on the subject: Taming the Wild Bitstream

     

    A really good way to get started is to download the free vendor tools and try them out.  I mostly use Xilinx, but a lot of people prefer Altera.  You can then make sure you can work through tutorials and produce bitstreams and see if this is going to be something you're interested in before even buying a development board.

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