gcvideo - Open source GameCube component cable solution

Discussion in 'Modding and Hacking - Consoles and Electronics' started by darcagn, Aug 31, 2014.

  1. Helder

    Helder Site Supporter 2014,2015

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    I'm interested in what that costs, you likely have to commit to a large run for them to do it I assume.
     
  2. beharius

    beharius Resolute Member

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    If the price will be reasonable... Only disadvantage is not everyone can install it, like a jrok board, needs drilling on the back cover, I am considering it something easier to install. In the end price is important... An HDMI version would be cooler..
     
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  3. Marmotta

    Marmotta Dauntless Member

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    I still think there would be enough demand for it (obviously depending on price) amongst people who would know how to install it for personal use or provide installation services for other people. Agree that an adapter back plate, like the ones Buffalowing designed for the NES, would be preferable, but it's not a deal-breaker.

    I was considering attempting to component mod some PAL Gamecubes using the RGB signal from the analog AV port, but obviously this solution is far better.
     
  4. Riki

    Riki Peppy Member

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    Yes, DVI (HDMI) version would be cooler. For Wii too.
    Suggested Spartan 6 FPGA (which one btw) is quite pricey though.
     
    Last edited: Sep 2, 2014
  5. Unseen

    Unseen Spirited Member

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    XC6SLX4, maybe XC6SLX9 if you want additional features like an OSD for configuring things like scanlines. Another route would be a DVI or HDMI encoder chip (e.g. ADV 7511/7513 or TFP410) and a smaller FPGA (i.e. XO2), but from what I've seen the combination of encoder chip plus XO2 tends to be more expensive than the Spartan 6.
     
  6. Calpis

    Calpis Champion of the Forum

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    For HDMI (with transmitter chip) you don't need a FPGA since colorspace conversion isn't necessary, a small CPLD can unpack the GC's 4:2:2 and feed it to the transmitter. The transmitter will also support I2S directly so the design is dead simple.
     
  7. Unseen

    Unseen Spirited Member

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    The last time I tried to synthesize the design for a CPLD (without color space conversion), it was about 160 macrocells of an XC95288XL. If you can optimize it enough to fit into an XC95144XL, you have successfully managed to switch out the XO2 FPGA for a CPLD that costs approximately the same (or more) and comes in the same-sized package.
     
  8. Calpis

    Calpis Champion of the Forum

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    To unpack/deserialize a ITU-656 stream should take 16 DFFE to hold Cb and Cr and 24 to synchronize them with Y = 40 DFFE. On top of that you need a couple bits for a state counter and maybe a few for sync delay. That should fit into a XC9572XL.

    All the metadata obviously takes a ton more logic to decode, but that shouldn't be necessary unless a transmitter trips up when the GC changes video modes or something.

    It also seems that the popular ADV7511 takes 8-bit "DDR" ITU-656 directly, so it could be that additional logic isn't necessary at all.

    After reading the GameSX wiki page I'm almost positive it can be implemented off-the-shelf.

    For analog YPbPr or VGA the ADV7392 looks suitable as well (appears to need external reconstruction filter and coax driver/amp).
     
    Last edited: Sep 2, 2014
  9. Unseen

    Unseen Spirited Member

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    Oh, neat - I didn't know about that format. It's quite similar to what the Gamecube uses, but it's not identical. In particular the Cube does not use SAV/EAV codes but instead signals the presence of blanking using Y=0 and encodes the flags in the following chroma sample.

    If it's that simple, just go for it and be the first who provides a GameCube to HDMI interface. I would probably buy one.
     
  10. Calpis

    Calpis Champion of the Forum

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    Perhaps, but I suspect that it is at least compatible with BT.656 and that the wiki's flags actually are SAV/EAV codes.

    The logic (or lack thereof) is simple. I don't think the manufacturing side is simple when dealing with custom connectors or low-demand items. Maybe one of the project vultures will attempt it.
     
  11. billcosbymon

    billcosbymon Guru Meditation Error

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    I am also very very very interested!
     
  12. Unseen

    Unseen Spirited Member

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    I'm sorry, but I have to disagree on that. The logic analyzer capture below shows the change in the signal from the active area of the video signal (which is black - luma 0x10, chroma 0x80) to the blanking area. An 8-bit BT.656 video signal would send "0xff 0x00 0x00 <flags>" at this transition, but the cube just switches to luma 0x00 and flags in every chroma byte.

    gcdv-blanking.png
     
  13. Calpis

    Calpis Champion of the Forum

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    It's more of a question of how a BT.656 receiver would interpret the codes. From what I can see the GC's flags align perfectly with BT.656 flags, so if GC inserts the codes at the correct time, and the receiver ignores the non-sync bits which have been repurposed, it should be compatible. It's pretty clear that the I/F at least started out as BT.656, so it must have targeted a standard receiver, probably for encoding purposes at some point.
     
    Last edited: Sep 2, 2014
  14. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

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    You wouldn't need to drill or modify the case, really. There are two good solutions for the connector situation:

    1. Just use the multi-out connector. On NTSC GameCubes, the RGB pins are unused. While I don't like the idea of doing something non-standard with a connector that has always had a standard pinout, I don't see the downside of doing this. Just output YPbPr on the pins that are reserved for RGB. It would require custom cables to be made, but you can get fully pinned male multiout connectors for pretty cheap to make these cables. This won't work for PAL GameCubes though unless the owner was willing to lose RGB functionality forever.

    2. Desolder and remove the multiout connector from the GameCube and mount a Wii-style connector instead. Helder has already 3D printed a bunch of these (although some changes might need to be made for size/clearance inside the 'Cube). This way you could keep using a standard pinout and use all of the off-the-shelf first party and third party cables that exist for the GameCube's younger brother, the Wii. The downside to this is that the Wii connector uses mode-selecting pins, so some simple logic would have to be added in to select between video modes using these pins (unless you were willing to lose S-video for NTSC 'Cubes and RGB for PAL 'Cubes).
     
  15. Mord.Fustang

    Mord.Fustang Fiery Member

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    I'm curious to see how much these will be in comparison to the outrageously priced $100+ cables.

    I agree that HDMI would be a HUGE plus over a component version.

    Edit: VERY cool project BTW!
     
    Last edited: Sep 2, 2014
  16. beharius

    beharius Resolute Member

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    I received the prices. It can be done if we take min. 70 orders. I will have more in hand of course.
    Price is $50 including everything. Assembled in China totally, so expect a very clean work, factory made since they use stencils. What do you think?

    Btw last week I opened my Triforce. It uses this MX component IC too. It can be an alternative to find the Triforce and use the Mega's board (gc-forever)

    Darcagn, thanks for the idea,I was thinking the difficult way.
    there can be installers to make this modification, like Ape or James from JammaNation X.
     
    Last edited: Sep 3, 2014
  17. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

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    $50 is a good price to me! Is that just your production costs or does that include your cut of profit as well? The prices of the cable on eBay are in the area of $150-$180, so even though this requires installation, I think this will be competitive price wise against the official Nintendo cable.

    Another option would be to desolder the digital AV port (although Unseen said that this is difficult) and put a VGA port in its place and use this GCVideo board in VGA mode. It still wouldn't require any case drilling as the VGA port would fit in the space where the digital AV port goes. XRGB-mini users could then use a Kenzei to get 480p RGB out (XRGB-mini users prefer using the RGB port instead of the D-Terminal/Component port on the back as it has a better low-pass filter on the RGB port)
     
    Last edited: Sep 3, 2014
  18. beharius

    beharius Resolute Member

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    Yeah, I've included my profit too. I asked for the parts availability, and the answer is funny, China is the world factory...:)
    I would like to give a royalty fee to Unseen per board, if the project can be started.
     
    Last edited: Sep 3, 2014
  19. Unseen

    Unseen Spirited Member

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    Disclaimer: I suck at desoldering THT parts. The ground pins were the main annoyance and that connector has quite a few of them.

    EDIT: Which reminds me... If anyone actually builds the board, be careful when you connect it to the cube. One of the pins of the DV connector has 12V on it and the two pins next to it are needed for GCVideo. If you accidentally create a bridge there or miscount the pin number, you risk frying both the FPGA and the Gamecube.

    The GCVideo board also has a CSync output that can be directly connected to an XRGB Mini.

    If you really see a need for it, I could also add a mode for RGB output with sync on green.

    Note to self: Update my amazon wishlists and add the links to the project's README file ;)
     
    Last edited: Sep 3, 2014
  20. beharius

    beharius Resolute Member

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    Yeah, rgbs can be cool too.
    I hope those in the wishlist are not too heavy...:)
     

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