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15kHz protection dongle - Gambaman's VGA2SCART adapter


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Gambaman on the Arcadecontrols forum opensourced a PIC-based VGA-to-SCART cable adapter last year that seems pretty awesome.

http://forum.arcadecontrols.com/inde...,160869.0.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/inde...tml#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 (C-sync on pin 13 as expected) 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 who's 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 :)

 

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Edited by buttersoft
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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 - and for helping initial setup of an emulation PC, 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 icon_smile.gif

 

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

Edited by buttersoft
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  • 4 weeks later...

Shit, ok, i'll fix that tonight. My apologies, there were a few revisions and i must not have updated the link. Those ones were designed to fit in a DB9/DB15HD backshell with a cable out the other side.

 

EDIT: ok now i'm not sure. I ordered some from the post in the Arcadecontrols forum and they arrived fine two days ago, so I think the link is right. I've sent you a PM to try and clarify what's gone wrong...

Edited by buttersoft
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  • 4 months later...

I ended up re ordering the correct PCBs (I had used a different link) and made up the PCB.  Works fine.  Good thing to add as a backup but yes it would be good if the protection range could be dialed in for arcade monitor use.

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Yeah, i did take a look at the code in MPLAB IDE, but i had to study tutorials to even get the original code to compile. And any changes i make just fall over. I might come back to it some day...

Glad to hear it worked tho 🙂

Edited by buttersoft
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