gcvideo - Open source GameCube component cable solution

Yup I do own a xrgb mini, bought it from Yakumo on here. I have not got the Euro Scart to jp21 adapter yet, but have been buying up euro scart cables as I can find them.
So far I have snes, ps1, ps2, and 4 3-port scart hubs. I have a hd-pvr 2 and it does record 60fps, I tell it to scale down to 30fps due to storage space. I have had nothing but problems with the hd-pvr 2 to be honest, the only reason I keep it is due to it is the only device that still includes the toslink spdif port.

 

Hey Unseen, could this project work with the Sega Game Gear? I know Tim Worthington makes a GGTV board that does Composite, S-Video, and RGB so could what he did be done for digital HDMI and DVI output?

 

Not as-is - the Game Gear uses 5V-logic, connecting it directly to the inputs of the FPGA would destroy it. Also, the "firmware" for the FPGA would need to be rewritten.

 

When the other versions are done or when you have the time, would you be willing to look into it? Is there a way to lower the voltage so we could use the same FPGA?

It might be a tight fit to mount the FPGA internally and if wire length is an issue, then the only way to keep it external would be to use something that attaches to the system like the PowerBack rechargeable battery accessory so it could hold the FPGA and its components while keeping the wires as short as possible. Turning the GG into a console might be a better option, since you could keep it completely internal and have a custom case for the system.

It would probably make screen replacements easier because you could use a small HD monitor and get better quality than those SD Composite monitors.

 

Sure, but that needs additional components, i.e. a new or an additional PCB.

If an LCD replacement is the goal, driving the LCD directly instead of converting to some intermediate standard may be a better option. Are there even any LCDs available that are about the same size as the original, have a sufficiently-small controller and accept a better signal than composite?

 

How could we make an add-on board that does this?

Sorry if it came out as that. My goal was to hook it up the Game Gear to an HDTV or monitor via HDMI or DVI instead of analog Composite, S-Video, or RGB. I'm not sure if there are any screens like that, but if there are, they are probably expensive.

 

The same way other circuits are built too: Figure out what you want it to do, design the circuit, draw some schematics and build it - either using a prototyping method like perfboard or by creating a layout for a printed circuit board that you then either etch yourself or order from a PCB house.

Ah, I misunderstood you then. Since there seems to be enough information about the GameGear's internal video bus available, it should be possible in principle. Removing the large black border around the picture will most likely not be possible though.

 

It's ok. Doesn't Tim's GGTV board have a switch for disabling the video compression, making games output at fullscreen, or is it just disabling video compression for Master System games played on the Game Gear? I've seen a video on YouTube that certain Game Gear games actually output in fullscreen when hooked up to a TV, even with video compression enabled. It was one of the Mickey Mouse games. I can link the video if you want.

 

The video compression you're referring to is the compression when playing Master System games on the Game Gear. The video for actual Game Gear games isn't compressed at all. The reason for the switch is the compressed video doesn't display on the GGTV's video output. And the reason for not simply disabling it permanently is if you want the option of using the Game Gear normally, Master System games won't display on the LCD unless the video IS compressed.

Technically, all Game Gear games output full screen. The lower resolution Game Gear LCD only displays the middle of the frame. Most games just have solid colors outside of the area the Game Gear LCD shows, but I think some show graphics all the way to the actual video border.

 

Thank you for clearing that up. One of the Mickey Mouse games does in fact go to the edge of the video border when hooked up to a TV. I think its Castle of Illusion. I wonder if there is a way to make all Game Gear games go all the way to the edge of the video border. If there is, it would probably make the games look bad.

 

@MonkeyBoyJoey - I have some boards for the Game Gear that I made recently, and just so happened to have soldered the main CPLD chips onto four more last night.

They are still prototypes, but the video output is probably the cleanest and sharpest you're going to get.

It uses a Mega Drive 2 type mini-DIN connector for the video output.

The current version only outputs RGB atm, but it has some DACs onboard for possibly doing composite / S-Video encoding too.
It may need a CPLD with more logic on to do that though.

The proto boards also don't have the mounting holes on, so will have to be glued to the GG PCB or case.

They also fix an issue with Tim's original code - it didn't output the Red, Green and Blue pixels at exactly the same time, so added a fair bit of "ghosting" to the edges.
You can see this on the yellow edges on Sonic, or on the trees...

https://youtu.be/FiJL27Jy-rI?t=16m7s

AFAIK, the switch is for expanding Master System games to full screen on the video output, but doing so disables the internal screen.
(You also get some GG games that are essentially the MS version in a GG cart, like Castle of Illusion.)

The switch simply Grounds a test pad on the GG PCB itself, so it's not doing any "processing" on the CPLD or anything.

@adimifus is right though - all Game Gear games will only show a smaller image in the centre of the TV screen.
"Master System" games will do the same thing unless you flip the switch to expand it to full-screen (which then disables the internal LCD, 'cos it can't display it.)

The small image isn't really a big deal though, as it still looks great on the TV.
On many modern TVs you can even zoom in a bit more so it fills the screen better.

Not sure when I'll be doing the next round of PCBs for this though - these are just for testing atm, and I have two more GGs to mod.

Doing video expansion on all GG games would probably require some RAM to buffer the frames.
At the very least it would need an FPGA or CPLD with more logic on.

There may be some tricks for doing the expansion without external RAM though.
You can expand the lines horizontally quite easily, then use a small block of internal RAM to buffer some lines and expand vertically, and then adjust the sync timings so the TV would centre the image.

I'll post some pics of the PCB in a mo...

OzOnE.

 

I'm excited for those! I'm ok with it being just RGB, but if you would like to output S-Video, maybe a Sega Saturn 10 pin mini din would work better because then all you would need are Sega Saturn cables. I think those connectors are rare though. I didn't know his board had that issue. I've seen Luke's video on his Mega Gear and thought about doing that to my GG but ultimately decided that mine should stay portable.

Maybe just using the TV's zoom feature would be better then. If you can, could you look at what it would take for true digital DVI on a GG? Also, if you haven't already, I would recommend installing Tim's SMS FM Sound board in one of those GGs.

 

Thanks, I'll have a look at the Saturn cables thing.
I can probably find the sockets on AliExpress or elsewhere, but need to be sure I can still get the Saturn cables easily.

For Composite and S-Video, I'll probably just add a proper chip for it (like Tim's and other boards).

EDIT: I didn't want to sound critical of Tim's excellent work btw - I spoke with him via e-mail years ago, and he's done some great stuff. His original N64 RGB blog / code / schematic inspired me to play with HDMI on the N64 in the first place.

It's just that I noticed on Luke's vid that the GG video mod appeared to be outputting the pixels as soon as the colours are latched, hence giving the slight ghosting and strange edges in places. I'm assuming Luke is using the mod kit from Otaku's, so it's likely using Tim's original code as well?


I wanted to add Composite anyway so I can replace the LCD in the GG as well.
A pure digital connection to the LCD would be best ofc, but many of the cheaper "reversing camera" LCDs only accept Composite.

They should still be a huge improvement over the original screen.

For DVI / HDMI, I'm still trying to finish the board layout for the latest HDMI board, and almost ready to send off for proto boards.

The current board design is still around 47 x 39mm, but may still squeeze into the GG.

If the LCD is replaced too, it will definitely fit, since the CCFL backlight can be completely removed as well.
(The inverter for the old backlight is easily disabled too, just by removing the inductor for the power.)

It would be trivial to get the GG code working on the HDMI board.
The only problem is that some modern TVs won't accept 240p / 288p / 480i / 576i via HDMI, only 720p and above.

To "upscale" would likely require external RAM, but I may be able to do what kevtris does with his HDMI NES board...

As the NES outputs only 240p (or 288p) and generally doesn't change vid modes in-game (like the N64 does), he simply locks the HDMI output sync to the incoming sync from the NES. He can then just buffer a few lines an expand it to 720p etc. for the HDMI output.

I want to try targeting as many machines as possible with the HDMI board.
I'm constantly learning more about PCB layouts, so not sure I can stretch to adding SDRAM to the small board just yet.

With the right code though, it might be possible to do some basic scan-doubling to at least get it outputting 480p / 576p or 720p to the TV.
That would then pretty much guarantee it working with 99% of modern TVs out there.

Here are some pics of the GG RGB boards (hope I'm not threadjacking?)...

A few notes...

I put a footprint on the board for one of those rocker / joystick switches.
I thought it would be a good option for adjusting the brightness / contrast / colour on the LCD upgrades, but I might change the switch.

I know the wires are a bit of a mess atm.

The board is upside-down for the photo.
(I will probably move the mini-DIN to the other side of the board anyway, so it all fits the case properly.)

It needed a small mod where three extra resistors are added to the DACs (to get the video levels just right).
(This can be sorted just by using different resistor values, but I'll be getting new boards made regardless.)

You can see the board doesn't have mounting holes yet.

These issues will all be fixed in the final version. Hey, that's why it's called a "prototype", right?





OzOnE.

@MonkeyBoyJoey - look's like you were right - getting hold of the 10-pin mini-DIN sockets for the Saturn cables is near impossibru. lol



I just checked on AliExpress, eBay, and Mouser, and they seem very rare.
Mouser only list the 9-pin types as a maximum.

Oh well.
The 9-pin "Mega Drive 2" type sockets have enough pins for RGB, Composite, Stereo audio, +5V, and Sync, so it would be simple enough just to add a switch so it will output S-Video instead.

(ie. Chroma via "Sync", and Luma via "Composite" etc.)


OzOnE.
P.S. This discussion also reminded me that I need to add voltage level translation to the HDMI board for 5-Volt machines. doh!
(The Altera CPLD on the GG board can handle 5-Volt levels directly though.)

 

As far as I know support for either 480p or 576p are required for all HDMI sinks which can be created from a 240p or 480i signal with very little hassle on an FPGA (if it has enough BRAM). I didn't have any problems with 480i yet on the devices I tested as long as pixel doubling was used to ensure that the pixel clock doesn't drop below the 25MHz minimum. Some devices didn't like 240p via HDMI though.

 

I found a female 10 pin mini-din cable connector on eBay: http://www.ebay.com/itm/231500102105
It's not a PCB mount but it could still work.

I thought Luma was Sync information and Chroma was the Color info. Maybe try Luma via Sync and Chroma via Composite pins so you can create Sync on Luma RGB cables.

 

Yeah, I think 480p / 576p works on almost all TVs.

My Samsung is one of those that definitely doesn't like 480i / 576i via HDMI though, sadly.

Scan-doubling might be possible for the N64 (when it switches to interlaced), and other machines, but it's tricky with the small size of FPGA I'm using and no external RAM.

I'm looking to just get these boards made at first, as it's taking me way too long to get projects done.
I can then hopefully add SDRAM (or even SRAM) to it, to go from interlaced to progressive more easily.

True though - scan-doubling from 240p -> 480p, and 288p -> 576P should be no problem.

I tried enabling pixel doubling on the HDMI board for the Gamecube before, but the monitor still wouldn't accept it.
It would probably have far more chance of working on the TV, but I can't recall if I tried it on my Samsung.

I was hoping to try scan-doubling on the GG board, as well as converting the colour space to Component, but there's not enough spare logic on these chips (the ageing EPM7064).

I want to eventually get these boards out to people at a reasonable price, and it's difficult to know what people are prepared to pay for them tbh.
It's getting harder to find small non-BGA CPLD chips at a decent price, and the EPM7064 is one of the few that you can still buy and manually solder.

In other words - I'd love to put a larger CPLD on the boards, but I don't think most people would want to pay much above $40-50 for a kit.

OzOnE.

I've seen a few of those too, and the PCB mount sockets are likely available somewhere, but I'm worried that I won't be able to get a bulk load of them at a good price.

Strangely, the pre-made RGB SCART cables for the Saturn seem a fair bit cheaper than the MD 2 cables though?

(I actually had it the other way around originally, but then edited the post. lol)

I thought it made more sense to have Luma on the "Composite" pin, because then it would at least still give a B/W image if people had it plugged into Composite if the switch was set wrong.

AFAIK, the Chroma signal only carries the colour info, but with no composite sync...

http://en.wikipedia.org/wiki/S-Video

The other main difference between Composite and S-Video is that the Luma signal is not modulated by the Chroma, so you don't get that evil "running ants" or "dot crawl" effect on bright colours.

I doubt I'll be able to generate the Chroma signal on this tiny CPLD unfortunately, so it'll be easier just to stick a Comp / S-Vid encoder chip on the final board.

OzOnE..

 

That is strange especially since there are more Sega consoles out there that use the Genny Model 2/MD2 connector than Saturn consoles themselves. I'm not sure but I think the 10 pin mini-din male cable connectors are more common than their female counterparts. Maybe the 10 pin mini-din is making a comeback? If so then that is awesome and makes life so much easier!.. maybe.

All this talk about Saturns and their A/V ports makes me want one so badly but they are getting expensive here in the USA. ~$80 for a model 1 Saturn with a single controller and craposite AV cables and a power cord I already have is kinda ridiculous.

Lol. While S-Video is great and all, nothing beats pure 15KHz RGBS via SCART... except everything that came after it like 31KHz RGBHV VGA, DVI-D, HDMI, Display Port, Component (debatable), D-Terminal, etc.

I have to admit, while composite video sucks for normal uses, it was really helpful during my Genesis Model 1 region mod testing phases. I had to hook up the Genny to an old RCA Colortrak CRT to test if my switches were working right. Funny thing about 50Hz on US TVs, they display it but incorrectly. My CRT had the image flickering all over the place and my HDTV, which does NOT accept PAL (sadly), displayed the image in black and white but off center. Somehow Sonic 1 was still playable like that. I hooked it up to my converter via RGB SCART and everything works fine. How did you guys in PAL land survive with a slower Sonic 1? I had to get the speed shoes power up just for it to run at NTSC speeds!

Wait a minute. That last part gave me an idea! Would it be possible to include a way to put the GGs in the PAL format or at least NTSC50? It would be really helpful for Master System games that run too fast in 60Hz.

 

480i and 576i have half lines somewhere in the video iirc. Do you do anything special with those to get your progressive timing. Or does the TV not really care if there are also half lines in a progressive image?

 

The "half line" occurs in every field and the only thing that really makes it a half-line is the fact the VSync starts or ends in the middle of it instead of at the beginning. When the lines are processed just based on the HSyncs, the linedoubler always sees complete lines on the input and always outputs two complete lines for each of them. The only way you could get a half line on the output is if the start of the VSync signal was explicitly moved to the middle of a line, which would make the signal interlaced again (now 960i) - but there is no reason to do so.

 

I see, so if I understand it correctly, 240p and 480i have the same amount of pixels (including blanking) in a frame/field? It is just that the VSYNC timing is different.

Edit: not sure if my description is clear. But as I understand it, in 480i the VSYNC signal comes in the middle of a line and that is the only real difference? All lines are still the same length as in 240p?

Edit2: had a look on the decoded N64 VSYNC and HSYNC signals when displaying 480i. It seems to output 262.5 lines per field. On one of the fields it puts the VSYNC at the half of the 262nd line. So yes, I guess if you line double that you get 525 lines total, which is more accurate to specs than line doubling 240p (has 263 lines per frame). So I guess this also means the VSYNC frequency is slightly higher for 480i signals? I was hoping a 240p frame would take exactly as long as a 480i field but it does not seem to be the case for N64 and I also do not think it is the case for Gamecube, but have not checked it. Just wondering, does your TV lose sync for a while with the HDMI mod when switching to 480i if you have line doubling enabled?