GBS 8200/8220 CFW Project

[Ryoandr]

Board and/or scaler chip might be made with CMOS TTL in mind, which is 3.3v.

[MikeIronFist]

Board and/or scaler chip might be made with CMOS TTL in mind, which is 3.3v.

Wouldn't that make it totally unsafe for VGA then?

[Ryoandr]

VGA HV can be CMOS TTL I think.
CMOS TTL is usally enough to trigger 5V TTL

[rama]

Also I am still getting outstanding picture quality by pressing Gain - then Auto Gain Control toggle. The picture instantly brightens up and looks appropriate (e.g highlights are fine). I wish there was a macro to do this!

You don't have to press Gain -. Just enabling Auto Gain is enough, and it even stays enabled across resets.
The picture brightening up is part of the operation: The algorithm looks at the internal debug bus for brightness values, and particularly for clipping.
If it detects clipping, the brightness is lowered a step, up until it sees no more clipping.

The option is intended for sources with a below than normal RGB level. It should automatically bring them to the full range of the input ADCs.

[Gunstar]

Matt/gingerbeardman noticed a solderless solution being mentioned in the replies to amoore2600's GBSControl vid:

Sounds interesting, I guess you'd still need the other mods to help with noise etc.

[maxtherabbit]

Remember guys, you have to remove the 100 ohm sync->ground resistor when connecting a vga source.

So this has me wondering - and I hope this isn't an annoying question to ask - is this a situation where the RGBS pins and DSUB pins are tied together? And if so, then why exactly do we need the additional termination resistor for sync when using RGBS?

The board is designed to take standard VGA signals, and that's TTL Hsync and Vsync, which are 5v each, right? What's the danger of using an unterminated CSync signal in this situation? I'm not going to use RGBS without the resistor, I'm just wondering why the board can take VGA just fine(?) but somehow unterminated Csync (which I've never seen above 5v) is a problem.

Yes the inputs are tied together.

You do not need the additional resistor for TTL (or CMOS LVTTL) sync inputs. From the wiki:

Every GBS board comes with ~500 kOhm termination on the sync input.
This termination is meant for VGA and most arcade boards. It is unfit for most other sources however.
If you want to use the RGBS input for regular TV level sources (game consoles), the GBS requires one additional 100 Ohm resistor to ground on the sync input.
Together with the factory resistor of ~500 kOhm, this will bring the total termination close to TV levels of 75 Ohm.

(typo in that text - it's actually a 500ohm factory resistor)

I.e. you only need to add the resistor if your are driving the board with video level sync, which in my opinion shouldn't be done anyway. If you are using a console with native csync output just pipe it directly to the GBS, otherwise use a sync stripper.

As to whether 5v TTL sync is unsafe for the TV5725 - strictly according to the datasheet the maximum voltage on any input is VDD+0.3V. However, in practice I've driven it with 5V TTL sync and experienced no issues. It's well possible that it would degrade the IC over time doing this, but as cheap as the things are I'm willing to chance it.

The console output dongles I've designed for use with the GBS however are 100% safe to use per spec. They show 3Vpp at the TV5725 input.

[rama]

Fixed the wiki:)
And yeah, I'll go with 3.3V level sync being safe, most likely.
If you have 5V levels, consider adding a series resistor (around 470 to 680 Ohm) to protect the sync input.

[MikeIronFist]

Yes the inputs are tied together.

You do not need the additional resistor for TTL (or CMOS LVTTL) sync inputs. From the wiki:

Every GBS board comes with ~500 kOhm termination on the sync input.
This termination is meant for VGA and most arcade boards. It is unfit for most other sources however.
If you want to use the RGBS input for regular TV level sources (game consoles), the GBS requires one additional 100 Ohm resistor to ground on the sync input.
Together with the factory resistor of ~500 kOhm, this will bring the total termination close to TV levels of 75 Ohm.

(typo in that text - it's actually a 500ohm factory resistor)

Ah, thanks, good to know. Sounds like I could just put a resistor in series onto my adapter's sync line then. I think I would prefer that instead of using an additional termination resistor + needing a switch for when I want to use VGA.

I.e. you only need to add the resistor if your are driving the board with video level sync, which in my opinion shouldn't be done anyway. If you are using a console with native csync output just pipe it directly to the GBS, otherwise use a sync stripper.

Would video level sync be any sort of risk to the board/IC despite its typically lower voltages?

As to whether 5v TTL sync is unsafe for the TV5725 - strictly according to the datasheet the maximum voltage on any input is VDD+0.3V. However, in practice I've driven it with 5V TTL sync and experienced no issues. It's well possible that it would degrade the IC over time doing this, but as cheap as the things are I'm willing to chance it.

The console output dongles I've designed for use with the GBS however are 100% safe to use per spec. They show 3Vpp at the TV5725 input.

Fixed the wiki:)
And yeah, I'll go with 3.3V level sync being safe, most likely.
If you have 5V levels, consider adding a series resistor (around 470 to 680 Ohm) to protect the sync input.

Excellent, thanks guys. A series resistor is definitely the way I'm going to go for my setup.

[kitty666cats]

Matt/gingerbeardman noticed a solderless solution being mentioned in the replies to amoore2600's GBSControl vid:

Sounds interesting, I guess you'd still need the other mods to help with noise etc.

I asked nicely in this thread and got a pretty quick response from someone willing to throw one together for me (soldering noob, genetically inherited hand tremors - I was not at all confident in throwing one of these together). I'm counting myself quite lucky, there's probably not too many other places online where someone can go and ask / get such a quick response <3 you folks

https://www.ebay.com/itm/RGB-SCART-to-V ... 4470973527

https://www.youtube.com/embed/Ts6uDrBYKhU?rel=0

^ there is this fuckin' thing, but... bleh. Ugh. Ridiculous price and zero mention of the fact it's just a GBS8200 / no credit given to rama and co.

[Gunstar]

Matt/gingerbeardman noticed a solderless solution being mentioned in the replies to amoore2600's GBSControl vid:

Sounds interesting, I guess you'd still need the other mods to help with noise etc.

I asked nicely in this thread and got a pretty quick response from someone willing to throw one together for me (soldering noob, genetically inherited hand tremors - I was not at all confident in throwing one of these together). I'm counting myself quite lucky, there's probably not too many other places online where someone can go and ask / get such a quick response <3 you folks

https://www.ebay.com/itm/RGB-SCART-to-V ... 4470973527

https://www.youtube.com/embed/Ts6uDrBYKhU?rel=0

^ there is this fuckin' thing, but... bleh. Ugh. Ridiculous price and zero mention of the fact it's just a GBS8200 / no credit given to rama and co.

Sorry to hear about the hand tremors and I'm glad someone got you one of these things set up. I think I've seen that particular encased scaler before, it's a silly price indeed.

I don't know what this solderless solution is but excited to see more people get on board with GBSControl and anything that flattens the difficulty curve of building it is a big plus. Kind of surprised a fully moded system isn't being produced in China considering there are OSSC clones.

@rama you need your 'buymeacoffee' link in your signature, get paid, son!

[kitty666cats]

@rama you need your 'buymeacoffee' link in your signature, get paid, son!

This x1000

[maxtherabbit]

Would video level sync be any sort of risk to the board/IC despite its typically lower voltages?

No

I recommend against it for performance and compatibility reasons, not dangerous though

[rama]

@HylianLink
That could have been the thing that killed the dongle, yes. The resistor increases current.
A well designed circuit should be able to drive such a load, but cheaper stuff may give out.
I wouldn't have expected it to get hot and die though. Maybe something else was bad / marginal before.

Hm, the scaler that doesn't give any credit or mention the source, that's kind of sad.
Open source allows this though, as long as he they share their modifications (which would be the case, I suppose).
Cheers for the heads up

[MikeIronFist]

Remember guys, you have to remove the 100 ohm sync->ground resistor when connecting a vga source.

What can happen if I use vga with the resistor?
Asking this because I forgot this recommendation and plugged a cheap hdmi ->vga dongle to test my raspberry pi(with recalbox on 240p) on the gbs. After some seconds playing, blackscreen. The dongle was hot. Never worked again. Is this damage relative to resistor?

I would assume you just had a faulty HDMI-to-VGA dongle before anything else. They're usually made super cheaply and often have poor quality control; in my experience, one had audio output that clipped/distorted, another one had jailbars and its left and right audio channels flipped. UGREEN has been the only brand I've tried that seem to have some sort of quality control and that might just be luck on my part.

Before learning about GBS Control, though, I used an HDMI-to-VGA dongle with similar 75 ohm termination on the HSync line to get RGBs from MiSTer in direct video mode. The dongle never heated up or misbehaved in any way. It would be really unusual for termination/attenuation to have any effect on the dongle side of things in the first place, so I would be surprised if it wasn't just faulty hardware/bad luck.

[hellbelly]

Regards that scaler on eBay, I get the impression it’s a bog standard 8200 board in an enclosure with a sync stripper. Yep, it’s misleading to buyers but I don’t think it’s using gbscontrol.

If it was using gbscontrol, would it need the 4 buttons from the 8200 board extended to the outside for example?

[kitty666cats]

Regards that scaler on eBay, I get the impression it’s a bog standard 8200 board in an enclosure with a sync stripper. Yep, it’s misleading to buyers but I don’t think it’s using gbscontrol.

If it was using gbscontrol, would it need the 4 buttons from the 8200 board extended to the outside for example?

It's implementing the remote phone app and comes with printed instructions, my guess is they were too lazy to update their old design and just kept the buttons

[hellbelly]

Oh man, that sucks

[hellbelly]

Heya

Just gave them a whirl, and my TV still reports back unsupported mode and gives me just audio. I've lost track of the different settings I've tried in the past - but remember changing the Hsync tolerance as it seemed like a big jump from the default value, so stuck in my mind.

My CMVS is a MV-1C with this board to get the video levels correct - https://oshpark.com/shared_projects/7gCyMb6I (just remembered that this design has been updated, just one component changed I think which I guess I should check now too). I also installed a DFO from JNX to try and improve compatibility - but again my Sony doesn't like that either.

It would be nice to get the CMVS -> OSSC -> Sony to work, but I now at least have CMVS -> GBSControl -> Sony working oh, and MiSTer if I don't fancy real hardware.

Cheers
Pete

Still impressed with this. In fact, it allows me to play my CMVS on my Sony TV which is really picky, couldn’t do this through my OSSC no matter what setting I changed.

Pete

@hellbelly Going a bit off topic here, but did you try these settings on the ossc?

Sync OPT. -> H-PLL Post-Coast - 2 lines
Sync OPT. -> Hsync Tolerance - 8.30us

Sent from my SM-G955U using Tapatalk

[NoAffinity]

As long as it works! I personally like the gbs output and the ossc output equally well for neo geo. Ossc gets razor sharp pixels to my 49" flat panel. Gbs is fun for running different resolutions and getting almost as sharp pixels on my 17" pc crt monitor. And then there's taking gbs pass thru to a VGA-to-ypbpr transcoder to sony trinitron 27". The gbs gives great flexibility in being able to resize the image and tune color gain.

Sent from my SM-G955U using Tapatalk

[Fluor]

Has anyone tried inputting VGA HV or VGA S and output YUV/YPbPr?

I was thinking how awesome would be to not need the CRT-Emudriver to connect a PC to a 240p, 15khz consumer set CRT.

[kitty666cats]

Anybody messed around with using theirs for video content, like Laserdisc or VHS? I've got various decoders and other devices so that I can connect a VCR or LD player via 15kHz AND 31kHz RGBS, RGBHV or YPbpr. There's too damn many possibilities, heh. Add a video processor into the mix and I'm just giving myself a headache - tryin' it out in a chain BEFORE the GBS, AFTER the GBS, etc etc... curse my morbid curiosity

[MikeIronFist]

Had fun experimenting with different devices last night. Turns out a Retrotink 2X in passthrough mode with an HDMI-to-VGA dongle + GBS control gives you a super easy option for S-video and Composite upscaling.

Here's Mario Tennis on N64 via S-video. Not exactly razor sharp - it IS still N64 - but the possibilities are pretty exciting:

Spoiler

[rx7turbo233]

I just installed the gbs control software on the gbs8200
I tried on different monitors but i have the picture has a little shack to it while it's showing I was trying to see if anyone can help I have nothing done to the gbs8200 I tried on my old lcd and it still has the slight shake every 20 second or so , I was wanting to know if it could be that the resolutions that the gbs control outputs could be that my monitors or LCD TV doesnt like it it's a little shake I don't know how else to describe it , what hardware mods should I do to it to get it to not do that

[rx7turbo233]

If anyone can help me that would be great thanks

[maxtherabbit]

I just installed the gbs control software on the gbs8200
I tried on different monitors but i have the picture has a little shack to it while it's showing I was trying to see if anyone can help I have nothing done to the gbs8200 I tried on my old lcd and it still has the slight shake every 20 second or so , I was wanting to know if it could be that the resolutions that the gbs control outputs could be that my monitors or LCD TV doesnt like it it's a little shake I don't know how else to describe it , what hardware mods should I do to it to get it to not do that

when you say shake do you mean the picture moves up and down?

[NoAffinity]

And what is your source?

Sent from my SM-G955U using Tapatalk

[rx7turbo233]

It has like a shake side to side , I followed all the instructions exactly , I'm using component with Sega Genesis model 2 with hd retrovision cables





It like a shimmer left to right like a power issue. But I'm using a 5 volt 2 amp power supply

Could it be I have to change resistor c11 with the 22uf 16 v

Causing a power wave in the picture I set it to the default

[rx7turbo233]

The picture shakes like a ripple left and right like having a issue syncing a little but I tried at default resolution on 4 monitors and the same

[hellbelly]

Did the same thing happen with your GBS board before you did the mod?

If you have another PSU, I would try that. Look to see if any other equipment you have uses the same specification PSU.

[rx7turbo233]

Worked fine before the
mod