Video issue in arcade cabinet

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TJ80
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Video issue in arcade cabinet

Postby TJ80 » Tue Feb 04, 2020 11:18 am

Hi,

I hope someone clever can help! :) For some reason I'm really struggling to get my MISTer working properly with the 15khz RGB CRT monitor in my Jamma arcade cabinet - my plan was to finally replace my old PC + ArcadeVGA combo. I have the v6 IO board and 64mb SDRAM module and can get everything working well over HDMI. However, I have two problems when hooking up to the arcade monitor:

1 - The green channel is entirely missing - red and blue are fine, green is totally absent.
2 - I cannot figure out the proper settings to get vertical arcade cores to rotate for my horizontal monitor.

The missing green signal is very odd. I am 100% certain that the cabling from the VGA connector all the way to the monitor is good as I have tried swapping the red, green and blue signals around - the MISTer is simply outputting nothing on the green signal pin when configured for 15khz output. :( I don't think it's a hardware problem, because if I reconfigure with scandoubler enabled and try on a 31khz VGA monitor the green signal is present and correct.

As for rotating vertical cores, the image is brilliant (apart from the missing green) with the default settings but vertical arcade cores are unusable and don't seem to have a rotate option. If I enable the scaler on VGA I can rotate the image, but I can't get a decent picture - anyone have a good custom video mode they can suggest?

Many thanks,
Tim

Sorgelig
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Re: Video issue in arcade cabinet

Postby Sorgelig » Tue Feb 04, 2020 6:24 pm

TJ80 wrote:As for rotating vertical cores, the image is brilliant (apart from the missing green) with the default settings but vertical arcade cores are unusable and don't seem to have a rotate option. If I enable the scaler on VGA I can rotate the image, but I can't get a decent picture - anyone have a good custom video mode they can suggest?

you can't.
You need to rotate your monitor physically. This is how most arcades are designed. You've choose a raw video output (VGA), so you get what original arcades were output. More over - you will have to deal with the fact that some arcades are 90deg while others are 270deg.
There wasn't standard for arcade design, so don't expect any "common" standard for all.

TJ80
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Re: Video issue in arcade cabinet

Postby TJ80 » Tue Feb 04, 2020 8:11 pm

Thanks - annoying but makes sense. Anything doable with the scaler?

If not I can live with horizontal only - if only I could get the green channel working!

Cheers,
Tim

TJ80
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Re: Video issue in arcade cabinet

Postby TJ80 » Wed Feb 05, 2020 1:59 pm

A couple of updates having tried some suggestions from djlegion who has a video showing this working on YouTube:

- Tried changing the SOG switch. No difference, green still missing and no visible change to the picture other than shifting a pixel or two to the left.
- Tried setting ypbpr=1. The "static" pattern appears with green still missing, then the screen goes blank after a couple of seconds (no menu showing).
- Tried copying the MISTer.ini settings from djlegion's video, no difference.

So unless something has changed in the past year I can only think I have some kind of hardware problem - maybe on the IO Board. Does anyone know what might cause the green signal to be missing when set up for 15khz RGB but present and correct on 31khz VGA? I can't find any documentation about the SOG switch on the IO Board, is it suspicious that it makes no difference to the image? If set incorrectly would the monitor not lose sync?

Many thanks,
Tim

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Re: Video issue in arcade cabinet

Postby Sorgelig » Wed Feb 05, 2020 2:57 pm

There is no problem with green from MiSTer. Be sure you wouldn't be a first who notice the problem if there would be real problem with MiSTer. This is specific to your setup / something is broken.
I suggest you to try MiSTer on normal monitor or TV with RGB/VGA input. Then depending on result you will see if problem is in your MiSTer or Arcade monitor.

TJ80
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Re: Video issue in arcade cabinet

Postby TJ80 » Wed Feb 05, 2020 3:29 pm

Thanks.

That's the odd part - green is working fine if I connect to a 31khz VGA monitor with scandoubler=1, which is why I assumed it was a problem with my arcade monitor or the Ultimarc JPAC I use to connect it. I even replaced the video op-amp chip on the JPAC (made no difference). That's when I tried swapping the R/G/B signals and confirmed that the JPAC and the monitor work fine but that there is no signal from the green pin of the VGA connector when outputting 15khz! If I feed the green output (pin 2 of the VGA connector) into the red or blue inputs (pins 1 or 3) I get nothing, yet if I feed the red or blue outputs to the green input I get a green image displayed.

I think the next step is to put a scope on the green pin to 100% confirm there's nothing there - perhaps there's something the monitor just doesn't agree with for some reason!

Cheers,
Tim

TJ80
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Re: Video issue in arcade cabinet

Postby TJ80 » Sun Feb 09, 2020 7:50 pm

So I've made a little progress - bought an HDMI to Vga dongle to try the direct video mode and - lo and behold - glorious colour! So the problem is definitely with either my config (thinking not now) or my IO board. Looking at the schematics the green signal is a bit different to the red and blue, which just come straight from the DE10. If I don't need to use sync on green and just want a raw green video signal can I just connect direct to the DE10's GPIO pin in the same way as the red and blue signals?

Thanks,
Tim

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Re: Video issue in arcade cabinet

Postby Sorgelig » Mon Feb 10, 2020 11:30 am

TJ80 wrote:If I don't need to use sync on green and just want a raw green video signal can I just connect direct to the DE10's GPIO pin in the same way as the red and blue signals?

yes, you can. But Direct Video you already tried is better.

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Re: Video issue in arcade cabinet

Postby Threepwood » Tue Feb 11, 2020 7:13 pm

FYI:

I have the same issue that on VGA the Green Channel is suddenly gone (SOG OFF) or the image is too green (SOG ON). Weird enough only one of my MiSTers is having this issue, the one with an I/O 5.5. The newer one with an I/O 5.6 XL is still working fine.

Downgrading did not help, so I guess it is indeed a hardware issue.
2x MiSTer FPGA: [Official Stormtrooper Case, USB Hub 2.1 with Bridge Board, 128MB SDRAM, ADC, RTC 1.3, I/O v5.5] + [3D printed MiSTer XS Case v2, 128MB SDRAM, I/O v5.6 XL]

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Re: Video issue in arcade cabinet

Postby leejsmith » Fri Feb 14, 2020 11:31 am

Hi, did you make any more progress ? it looks like no luck so far since our email contact. I was wondering if you have any other VGA devices you can run through the jpac to the CRT or is that what you did with the hdmi > vga adapter ?

TJ80
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Re: Video issue in arcade cabinet

Postby TJ80 » Sat Feb 15, 2020 1:31 pm

I've fed the direct HDMI-VGA converter through the Jpac and that's working perfectly. So it's definitely a problem with my IO board or my Mister config! I suspect there's a hardware problem with the SOG circuitry on the IO board. For now I'm happy using direct video, but it's annoying not knowing what's wrong (plus with direct video I can't experiment with the scaler and rotating vertical cores)!

Now I just need to figure out why some Neogeo cores sometime have corrupted graphics (various numbers of reboots fix them, SDRAM tests fine...) and how to map the player 2 controls! Problems for another thread!

Cheers,
Tim


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