Gambaman's VGA2SCART adapter

[buttersoft]

Gambaman on the Arcadecontrols forum opensourced a PIC-based VGA-to-SCART cable adapter last year that seems pretty awesome.
http://forum.arcadecontrols.com/index.p ... 869.0.html

There are links in the OP to a couple of sellers, along with a few mods i made to it - the last of those being a double-ended passthrough dongle. This one does not have audio, and delivers 5V for blanking - yes, a little high.
http://forum.arcadecontrols.com/index.p ... msg1733596

Essentially it plugs into a VGA port, and any passive VGA-to-RGBS/SCART or whatever cable comes out the back. You feed it 15kHz RGBHV, and it passes RGBS and turns on the green LED. If the sync rate is higher it blocks the sync signal completely and turns on the red LED (RGB still passes, but without sync it can't hurt anything.)

Yes, i realise i can get c-sync out of CRT-emudriver, but even with Atom15 the sync jumps around on boot, and, as anyone whose used crt_emudriver excessively knows, very occasionally things go sideways. I'm not knocking it in the slightest, but arcade monitors for one can be pretty twitchy. And when you look at it, nobody's CRT is getting younger.

I hope someone can get some use out of this one. Build instructions and downloads are all in the ArcadeControls thread





EDIT: False alarm, i think. Someone must have ordered the old revision, but the link on ArcadeControls should be good. Just make sure to click the right link and look at the board you're ordering. The earlier revision is single ended and designed to make cables with.

[Gunstar]

I built the cable version (pre-buttersoft redesign) and it works well but was a pain to solder up the SCART end, this new version looks to be easier to make although there's no audio passthrough I think? still, nice to have an easy open-source design. I think Tim Worthington's design is also excellent and has an audio jack to pass on sound to the appropriate SCART pins, worth checking out for anyone considering buying one off the shelf.

[buttersoft]

Yeah, the one in the photos above is really just a DIY 15kHz protection dongle, that also happens to generate composite sync. It doesn't do audio.

[NewSchoolBoxer]

That the adapter gives the 12V for 4:3 (or less for 16:9) SCART television off the 5V VGA power is impressive. Meanwhile, I'm in US with VGA and BNC options only. I was going to nudge on if the 15kHz protection really mattered but in the linked thread:

I don't think any TV or PVM from about 1990 onwards would be damaged, they way they capture sync means they'll just fail to sync to anything outside their range. But i'm sure it's best to be safe. Some old Arcade monitors and older computer monitors certainly will be damaged, as they're circuitry was only meant to see 15kHz, and they will still work to capture whatever signal is input and damage themselves. They may not fail instantly, but in some cases the damage can be cumulative.

Makes sense to me. I like seeing a PIC processor in action and only $1! Had to study an 8-bit one in college. The C compiler and emulator were good enough.

[Gunstar]

Yeah, the one in the photos above is really just a DIY 15kHz protection dongle, that also happens to generate composite sync. It doesn't do audio.

This would be great for using with the mister. I suppose you'd need to disable C-Sync if it's generating its own.

[buttersoft]

This would be great for using with the mister. I suppose you'd need to disable C-Sync if it's generating its own.

Correct, it won't take C-sync as input, only H-sync and V-sync. But it works fine with MiSTer like that. In fact, when i was having trouble locating working HDMI-to-VGA dongles, i did manage to find one that would work ok at 15kHz but only with separate sync - so using this adapter worked great in that case

[Lawfer]

Yeah, the one in the photos above is really just a DIY 15kHz protection dongle, that also happens to generate composite sync. It doesn't do audio.

This would be great for using with the mister.

Can't you just use this?

https://retro-access.com/products/mister-io-scart

[Gunstar]

Yeah, the one in the photos above is really just a DIY 15kHz protection dongle, that also happens to generate composite sync. It doesn't do audio.

This would be great for using with the mister.

Can't you just use this?

https://retro-access.com/products/mister-io-scart

I'm using a similar cable but there's no sync protection, the dongle would offer peace of mind for when I'm using mister on a consumer set.

[buttersoft]

I should probably note that as a protection dongle this device is not perfect. It is great for stopping and diagnosing higher sync modes - say if your windows install suddenly decides to jump to 31 kHz or above - but it will pass anything from about 14 to 17kHz. Given most crt_emudriver or other PC setups will use from about 15.5 to 16.2 kHz at full range, the dongle is not going to properly protect something like a Nanao MS8 arcade monitor that needs to be working at its exact sweetspot of 15.75 kHz. Most arcade monitors would be perfectly fine, but i take no responsibility for yours

Gambaman does provide links to his code if you want to have a crack at refining it, however.

[Zebidee]

This would be great for using with the mister. I suppose you'd need to disable C-Sync if it's generating its own.

Correct, it won't take C-sync as input, only H-sync and V-sync. But it works fine with MiSTer like that. In fact, when i was having trouble locating working HDMI-to-VGA dongles, i did manage to find one that would work ok at 15kHz but only with separate sync - so using this adapter worked great in that case

Hi Buttersoft, love your work.

Hi y'all, this is my first post on shmups so please be gentle with me.

I have been using one of butter's 15khz dongles (thanks very much!) and I am very impressed, it is very neat and adaptable.

Regarding composite sync INPUT to that dongle: assuming uses XNOR logic for sync (I think it does) I believe the trick to getting it to work properly is to pull the unused V sync line (pin 14) to logic HIGH when taking composite sync input via H sync line (pin 13). You might be able to do that via editing the PIC so that it detects composite sync, but you could also do it by adding a simple switch (connect Vsync to your dongle circuit's Vcc input line).

I know this because I've just had to solve this exact same problem for the GreenAntz RGB/VGA to component transcoder - so I could use it with your dongle! Now in addition to RGBHV, GreenAntz now be used with RGBs inputs. This means GreenAntz will work with a wide range of VGA adapter dongles (DVI-VGA, DP-VGA, HDMI-VGA etc) that only pass composite sync (RGBs).

In other news, a SCART version of GreenAntz available soon. I see there is a SCART to component thread active here, so will probably pop in there soon to announce myself as well.

More info about GreenAntz RGB/VGA/SCART to component transcoder is available at forum.arcadecontrols.com
http://forum.arcadecontrols.com/index.p ... 245.0.html

[buttersoft]

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[Zebidee]

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I've been using your dongle with the GreenAntz RGB/VGA to component transcoder as an alternative source of composite sync for testing etc., and it all works well. I love the versatility of this, no need to change any settings, just plug it in. The dongle also cuts off out-of-spec sync during boot, which is a bonus.

SCART version of GreenAntz is now available.

http://forum.arcadecontrols.com/index.p ... 245.0.html