GBS 8200/8220 CFW Project

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Greg2600
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Re: GBS 8200/8220 CFW Project

Post by Greg2600 »

NoAffinity wrote:It says "Saturn rgbs/ypbpr out", via what looks like a genesis2/3 connector. Curious what they are doing there and what kind of cable you would need for the ypbpr part.

But, yes, in theory, if the sync combiner works for DC rgbhv input, then downscaling should work for it.

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Oh ha ha, I've seen them use a Playstation AV Multi-Out as well. I think they have them in excess, plus it enables a way to output component AV via a single port, and they include a cable like so for added cost. You'd think they would just use a VGA breakout cable, but maybe those are more money wholesale?

Image

I appreciate the answer though. Someone ordered one in the Facebook group, I'll see what his review is, but I may pull the trigger finally. I wish there were sellers in North America but there really aren't.
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

That cable looks like it's rgbs + audio. So I'm still curious about the Saturn rgbs/ypbpr statement.

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Kez
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Re: GBS 8200/8220 CFW Project

Post by Kez »

Hard to tell from the pictures but it looks like the 10 pin mini din connector that the Saturn uses, so it's probably just the same pinout. Then presumably it outputs RGBS or YPbPr depending on whether you enable YPbPr output in GBS-C.
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

Kez wrote:Hard to tell from the pictures but it looks like the 10 pin mini din connector that the Saturn uses, so it's probably just the same pinout. Then presumably it outputs RGBS or YPbPr depending on whether you enable YPbPr output in GBS-C.
That makes sense. Thanks for unraveling it!

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slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

I've just got hold of a Aliexpress pre-built device. I'll do a tear down and post photos once I know it's working okay, but it also has the Saturn output as well as a 5 RCA output labelled as RGBS Downscale, which sounds interesting! From what I've seen (on YT) the Saturn output can be used for downscaling without the hassle of combining the sync from the VGA RGBHV output. I've got a CSync Saturn SCART cable on order, so I'll give it a go when it arrives. (I'm hoping the port they've added is NTSC and not PAL pinouts otherwise I'll be pumping 9V+ into my TV instead of sync!)

ANYWAY, I do have two questions if you don't mind as I'm a bit worried my device might be faulty.

1) When using the SCART input with my Mega Drive(s) and my Dreamcast, the image jumps every few seconds. The cables are RGB SCART but they're wired for sync over composite and not using the dedicate consoles csync pin. Is it true the GBS Control really needs CSync to work properly and not Sync over Composite? The SCART input does work with my Pi2SCART device so I think it's working, but I'm a bit peeved that I can't get the Mega Drives to work with it as they were the reason for purchase (plus PC downscale).

2) How and what does passthrough actually do. I've connected things like my DC and Pi to the VGA input (with HDMI out on the GBS) but passthrough just shows a black screen. I'm not sure what it's used for now!
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

1) Just tested with my unmodified PAL Mega Drive II (with pretty noticeable jail bars too, lol), and didn't have any issues. Scaling up to 1280x960 on a PC VGA CRT.

How does that unit handle the 100ohm sync-to-ground resistor for RGBS sources? Want to make sure that is on, for said sources.

2) I believe pass through only works with RGBS inputs. I just tested pass-through and 15khz downscale from a modded Genesis 2 w/ 32x, outputting to a consumer CRT, and it had issues on both settings. Then, tested with SNES - dejitter and RGB modded (csync) - and had no issues in both modes. Tested w/ a stock Sega Saturn as well - no issues in either mode.
slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

Is your MD SCART cable using Composite Sync or Sync over composite?

There's no physical removable 100ohm resistor on the pins, but then I wouldn't expect there to be on a "professional" version of it. Remind me what this is supposed to do exactly? There IS a switch next to the VGA IN which I think they have labelled "force sync" :P and that "should remain off in most cases". I had assumed that might be the switch for the 100 ohm because if I switch it, the images goes completely garbled. It's also quite close to the pins where the resistor goes. I did also stick a 100ohm on it myself but it didn't stop the jumpiness.

I'll post some photos of the device and video of the jumpiness.

Weird that is also jumps on my DC via SCART but not my Raspberry Pi using Pi2SCART. That's a perfect image!
strayan
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Re: GBS 8200/8220 CFW Project

Post by strayan »

slikvik wrote: 2) How and what does passthrough actually do. I've connected things like my DC and Pi to the VGA input (with HDMI out on the GBS) but passthrough just shows a black screen. I'm not sure what it's used for now!
Passthrough mode: if you send it a component signal you can transcode to RGBHV. If you send it a RGBs signal it will output RGBHV (or component if you have it set to that).

I assume those aliexpress devices have sync cleaners on the SCART input already.
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

strayan wrote:
I assume those aliexpress devices have sync cleaners on the SCART input already.
Would they? essentially having a syncstrike built in??
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

Info on when and why the 100ohm resistor is needed, here: https://ramapcsx2.github.io/gbs-control ... oards.html

In short, gbs8200 was designed for arcade level video signals, and the 100ohm resistor attenuates for console level signals.

Gbs8200 has a built in sync stripper. If they've added one AND you have one in the cable, that could be an issue. I dont know that you have one in your cable, just speculating and looking for likely causes. Also, could be an issue resltuing from how your cable is attenuated.

Lastly, pass through mode will also be automatically activated with higher input resolutions that are beyond the limits of scaling.

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slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

Thanks for your time on this. I definitely don't have a sync stripper in my cables and they are CVBS, so if the 8200 is stripping the video from the sync, then that's not my issue unfortunately.

I'm confused that the 8200 has one built in though? This page actually suggests using one to improve compatibility:https://ramapcsx2.github.io/gbs-control ... ipper.html
Using a Sync Stripper
Compatibility with Sync-on-Composite or Sync-on-Luma can be improved by using a sync stripper, such as the LM1881.

RGBmod's video also suggests this.

Or are you saying that the Aliexpress sellers MUST have added one? Surely that can't be guaranteed given the many variants and manufacturers.

Here's videos of my issue. One is my MD and another is my DC:

https://www.youtube.com/watch?v=94wBLnmKVkg
https://www.youtube.com/watch?v=z06XXBhVr-U
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NoAffinity
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Re: GBS 8200/8220 CFW Project

Post by NoAffinity »

Seems I'm mistaken on the integral sync stripper. Thought I remembered reading that somewhere. Sorry for the mis information.

Oddly, the only console in my collection that my gbs has an issue with is that genesis 2/cd/32x setup with triple bypass mod. Ps1 luma, saturn luma, pal md2 sync on composite, no problems. But then again, that issue only arises when attempting to pass through via gbs which is unnecessary in my use case (scart to green antz to consumer set ypbpr input is much simpler).

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slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

Just to let you know it was the fact I was using RGB CVBS SCART cables. I've swapped the pin to use dedicated csync line of the MD/SMS with 220uf cap and 470ohm resistor and the image is perfect on both my Mega Drive and Master System! Will try my Saturn once I've fixed it!

Maybe it's just my device but it clearly doesn't like having the composite video signal mixed in with the sync!

(It tried the 100ohm on the sync/ground too but I'm assuming these Aliexpress devices must handle this on their custom PCB)

As an aside, I noticed it still has the RGB pots installed, but underneath, they have done this:

Image

Anyone know what this white stuff is that they've used to bridge the RGB pots?? ! :D
Last edited by slikvik on Sat Nov 26, 2022 9:56 pm, edited 1 time in total.
ldeveraux
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Re: GBS 8200/8220 CFW Project

Post by ldeveraux »

Aren't those just bridges?
slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

Well yeah, it's the RGB pots which should be bridged, but white things instead of wire? (Apologies, I should have made my post clear)
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

0 omh links are easier to handle than wires, no need to worry about melting insulation
slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

That's not like any 0 ohm I've seen before. It's literally white flat plastic. I mean it obviously is a 0 0hm link as you said, but still can't find anything on Google. I know that's a bit off topic! :D
Ryoandr
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Re: GBS 8200/8220 CFW Project

Post by Ryoandr »

It's not plastic, it's ceramic.
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valnesh
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Re: GBS 8200/8220 CFW Project

Post by valnesh »

About a year ago I decided that i wanted to build my own GBS-Control with built in HDMI out and USB-C for 5V power, mainly to see if I could. Since I had an old GBS-8220 that never worked I decided to disassemble it uh... not so gracefully.

Image

Which lead me to design the first version of my own GBS-C:
I decided to add two multiplexers, one to isolate the SCART and VGA inputs from one another and one to switch audio from SCART to component.
The SCART input has an EL1883IS for sync separation. The Si5351 clock generator is also on board.

On the output side I used a THS7373 and a MacroSilicon MS9288A for HDMI (Spoiler alert: unsuccessfully). On a side note, always check the datasheet to see if you actually used the correct footprint. :P

Image Image

After assembling the most essential parts I plugged it in and to my surprise there was an actual video output!

Image Image

After reworking the TV5725 and RAM the image cleared up and looked as expected.

Image

Sadly I couldn't get the MS9288A to work at all, which wasn't too surprising since I couldn't find a datasheet or schematic and I didn't have a working board with the same chip.
So I started looking for alternative chips, preferably with schematics and/or a datasheet. What I found was the ZY5621 and a single listing on aliexpress (which has since vanished as far as i can tell).
I just copied the schematic and created a small board to see if it actually works and it did!

Image

After all that my GBS-C ended up looking like this:

Image

Not exactly pretty but it works fine. :D
However the recent release of the Shinobi-Scaler made me want to revisist this project.

And this is the result:

Image Image

I removed the VGA and Component inputs since I don't use them and only left one video output using HDMI.
Very pleased with the results even though there are still some things to fix on this PCB.
slikvik
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Re: GBS 8200/8220 CFW Project

Post by slikvik »

Fantastic job!

I would only use Scart myself so this is a great idea. Probably a silly question but would it be possible with a slight redesign to reverse the input/output so that 480p could be fed into HDMI and downscaled to 240p?
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valnesh
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Re: GBS 8200/8220 CFW Project

Post by valnesh »

Possible yes, but it wouldn't be a small redesign.
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Gunstar
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Re: GBS 8200/8220 CFW Project

Post by Gunstar »

That looks great, valnesh
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Re: GBS 8200/8220 CFW Project

Post by SuperSpongo »

Looks awesome!
Taiyaki
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Re: GBS 8200/8220 CFW Project

Post by Taiyaki »

I’m amazed I never heard of this amazing project till today. As a result I’m doing a lot of catch up on learning about the functionality.

Is there any way to send a RGB input and back as RGB as the output?

I’d like to use one for my Dreamcast and PS2 on my CRT to play some 2D 480i games forced into 240p.

I also love the idea of playing Atomiswave games on Dreamcast on my CRT in 240p!
Guile
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Re: GBS 8200/8220 CFW Project

Post by Guile »

Taiyaki wrote:I’m amazed I never heard of this amazing project till today. As a result I’m doing a lot of catch up on learning about the functionality.

Is there any way to send a RGB input and back as RGB as the output?
If you use the vga input port on the gbs-c it needs to be RGBS input and not RGBHV. If you have an Extron rgb interface it works really well. Otherwise you can use the component input directly. I always use RGBHV output but it can output component too.

The downscaling is very good for both 480p and 480i. It gives very clean scanlines. The only issue is sometimes if there is a resolution change like 240p to 480i there is a strange glitch where the colors are wrong but if you toggle the output resolution it returns to normal.
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Re: GBS 8200/8220 CFW Project

Post by Bassa-Bassa »

Guile wrote:If you use the vga input port on the gbs-c it needs to be RGBS input and not RGBHV. If you have an Extron rgb interface it works really well. Otherwise you can use the component input directly. I always use RGBHV output but it can output component too.

The downscaling is very good for both 480p and 480i. It gives very clean scanlines. The only issue is sometimes if there is a resolution change like 240p to 480i there is a strange glitch where the colors are wrong but if you toggle the output resolution it returns to normal.
The thread is huge, I'm sorry - what exactly do you need and where do you buy it? Is there signal processing involved and has the lag been measured (if there is)?

Thks!
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Re: GBS 8200/8220 CFW Project

Post by Guile »

Bassa-Bassa wrote:
The thread is huge, I'm sorry - what exactly do you need and where do you buy it? Is there signal processing involved and has the lag been measured (if there is)?

Thks!
It depends on what source you're trying to downscale. As an example with the Dreamcast since it's RGBHV, you need to convert that to RGBS. Extron rgb interfaces are excellent for that, you can find them very cheap on ebay. The more expensive ones have vertical adjustment but you probably don't need that. You just connect the vga out from the Dreamcast to the vga input on the rgb interface, then you need a bnc male to vga male cable and connect the bnc to the R, G, B, S ports on the interface and the vga to the gbs-c vga input.

For component sources you don't need any of that and can just plug it straight in. If you already have a RGBHV to component transcoder you can also use that.

The video on the gbs-c by RGB Rob has the lag measurements and it is the fastest downscaler available, virtually lagless.
Taiyaki
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Re: GBS 8200/8220 CFW Project

Post by Taiyaki »

Guile wrote:
Taiyaki wrote:I’m amazed I never heard of this amazing project till today. As a result I’m doing a lot of catch up on learning about the functionality.

Is there any way to send a RGB input and back as RGB as the output?
If you use the vga input port on the gbs-c it needs to be RGBS input and not RGBHV. If you have an Extron rgb interface it works really well. Otherwise you can use the component input directly. I always use RGBHV output but it can output component too.

The downscaling is very good for both 480p and 480i. It gives very clean scanlines. The only issue is sometimes if there is a resolution change like 240p to 480i there is a strange glitch where the colors are wrong but if you toggle the output resolution it returns to normal.
Thank you for the reply. Sounds very promising.

I use Scart on my Dreamcast. So my input output would likely be RGB Scart to Component. Can I skip the conversion or is the Dreamcast Scart output also RGBHV? if it is I've been using it unconverted all these years. I've avoided using an Extron because the added features don't do much for my setup.

For the output if I go the Component route can I simply go with a passive (or active if needed) adapter/transcoder for Component to Scart to go back into my Scart switch box?

This device seems like a dream come true device for downscaling these 2D ports.
Bassa-Bassa
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Re: GBS 8200/8220 CFW Project

Post by Bassa-Bassa »

Basically, you need a DC VGA cable to get the console output RGBHV, otherwise it indeed outputs RGBS.

Don't expect everything to look well when downscaled for the reasons I mentioned in the other thread, but I guess that anything is better than vanilla CVS2 or MVC2.


Guile wrote: It depends on what source you're trying to downscale. As an example with the Dreamcast since it's RGBHV, you need to convert that to RGBS. Extron rgb interfaces are excellent for that, you can find them very cheap on ebay. The more expensive ones have vertical adjustment but you probably don't need that. You just connect the vga out from the Dreamcast to the vga input on the rgb interface, then you need a bnc male to vga male cable and connect the bnc to the R, G, B, S ports on the interface and the vga to the gbs-c vga input.

For component sources you don't need any of that and can just plug it straight in. If you already have a RGBHV to component transcoder you can also use that.
Ops, sorry for not explaining myself better, mate. I already have an Extron interface and I'd be using RGB, I meant which GBS device is the one to get as I'm a bit confused about this GBS thing. This seller says you need a GBS Control as well as a GBS-C AIO board?
Guile
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Re: GBS 8200/8220 CFW Project

Post by Guile »

Taiyaki wrote: Thank you for the reply. Sounds very promising.

I use Scart on my Dreamcast. So my input output would likely be RGB Scart to Component. Can I skip the conversion or is the Dreamcast Scart output also RGBHV? if it is I've been using it unconverted all these years. I've avoided using an Extron because the added features don't do much for my setup.

For the output if I go the Component route can I simply go with a passive (or active if needed) adapter/transcoder for Component to Scart to go back into my Scart switch box?

This device seems like a dream come true device for downscaling these 2D ports.
I rarely use Scart so I don't really know much about it. What kind of Scart cable are you using for the Dreamcast? I know there are some that combine sync so you might already have RGBS output.

For the gbs-c output you would need an active converter to convert component to RGB for Scart. It might be easier to use the RGBHV output and convert that to Scart instead.

Are you planning to make or buy a pre-made gbs-c? It looks like some of the new pre-made ones have Scart input but I don't have any experience with them, only ones I've made from stock boards.
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