Dreamcast to XRGB-mini

Um, the Dreamcast doesn't have component output....

EDIT: See here for more info that explains all of this: http://dcemulation.org/?title=Dreamcast_480p_XRGB-mini_Framemeister_Cable

 

Just in case he meant "composite": VGA or RGB - even without scaling - would be better than any scaled up composite.

 

Ah sorry about that. I could have sworn I remember seeing a Component out box or cable. I guess it might have been a crappy 3rd party deal.

 

VGA is absolutely stunning on the dreamcast, however, not all games are compatible. Luckily, we have beharius' VGA adapter which can do both 15khz and 31khz vga. The only thing is finding a display that accepts both those signals since most displays now adays are only 31khz stand alone.

 

15khz is just RGB. It's the same thing as buying a standard SCART cable.

 

a LOT of TVs don't scale the Dreamcasts VGA signal correctly. The Dreamcast is actually 720x480 not the more common 640x480 and lots of TVs detect is as 640x480 so the Mini can do a better job than a lot of sets.

Alternatively, if you don't want to use the Mini, get a VGA to component transcoder as TVs generally expect 720x480 via component.

Edit - Also meant to say, recommended settings can be found on the XRGB Wiki, though it seems to be having issues at the moment:- http://junkerhq.net/xrgb/index.php/XRGB-mini_FRAMEMEISTER

 

anyone has any info on how to modify my HAIS vga box to also output a 31khz RGB signal suitable for the mini?

 

On the VGA connector: pins 1/2/3/13/14 are red/blue/green/hsync/vsync.

You need to convert hsync/vsync to csync by using a sync combiner circuit like so:

Use the RGB signals from the VGA port and the combined sync from the circuit as input to the framemeister's RGB port.

 

^ thanks for that!
just to be 100% clear I got this correctly , I will be using straight connection from the vga port as RGB signals from the mini and then with the schematic above I will use the HV points on the vga port to make a CSYNC signal to feed to the mini:



so basically I will be getting 2 kinds of output with the box in VGA mode at the same time: a normal vga output and a RGBs one , correct?


edit:
atm I am trying to use the mini with a normal scart RGB cable, my God it's horrible!!! I can't get a picture at all. It's the first console that acts like that with my mini, I found that sync_level 18~20 lights up the input led and I get a picture but it loses sync offten. Any other setting and the mini won't see a signal at all or it will just blank screen... frustrating!

 

You got it! You'll be getting normal VGA and 31KHz RGBS at the same time.

As a bonus, the Dreamcast still produces h-sync and v-sync when in 15KHz mode, so if you put a switch on VGA select pin (pin 7 on the AV plug) you can toggle that RGBS output down to 15KHz (normal RGB SCART) and use that same output for games that don't support VGA mode but do support RGBS mode.

On page 2 of this thread you can see a pic of it on my VGA box

 

^ excellent, thanks a mil for the info, I shall get to hacking tomorrow

another clarification (LOL) , since my box already has a TV/VGA switch, do I still need to add a switch on pin7 ?
wouldn't my new framemeister port with the 74LS86 output a 15khz signal when the box is on TV mode?

 

nope, the TV/VGA switch is for pin 6 AND 7 together

TV mode = composite/svideo, but no RGBS or VGA (pins 6 and 7 floating)
VGA mode = 31KHz RGBHV (pins 6 and 7 both grounded)
RGB mode = 15KHz RGBS (pin 6 grounded, pin 7 floating)

 

ah, now I get it... thanks for all your help and patience
I'll return with some modding pics later....

 

not a problem, good luck!

I'll check back tomorrow to see how you're doing

 

Well , I couldn't do anything today because I needed to order a 74LS86 , turns out I didn't have one available...

But I did some thinking/planning , I decided not to add a 2nd port on the vga-box and use the existing vga one - due to lack of space in it.

So I will isolate the H+V pins and put a switch between them so you can select what signals go to the vga port: either normal vga H+V or combined sync.
I also decided to use 2 of the unused vga pins (they are isolated on the box from the factory) as audio-out pins , so audio can be fed to the mini. Once again there will be a switch for these pins to select floating (for vga mode) or audio (for mini mode).
And ofcourse I will add a 3rd switch to enable 15khz vga , it should work fine on the mini with the audio-switch enabled.

So I made a custom vga cable for now that will connect from the vga port to the mini and carry audio as well:




edit: allright made a crude pic of what I plan to do: (WARNING , some pins are wrong on this preliminary drawing)

 

Sounds like a plan Keep us updated!

 

Allright! Today I got busy , made the sync circuit and checked that everything will work as planned. And it does!
The framemeister now works perfect with RGBs , in both 15 kai 31khz modes

I found that it's pin6 that controls 15/31khz output, pin7 is always grounded in VGA/RGBs modes. So if pin6 is floating you get 15khz , if it's grounded you get 31khz output.
I also found that the Hais box has non-standard wiring, I made a picture in case anyone else in the future wants to have all this information gathered:




mine looks like this atm, I only installed the "vga audio" switch, will continue with the rest tomorrow... it works great with the custom vga->framemeister cable I made that uses the 2 n/c pins for audio, the switch either connects audio or nothing at the pins to ensure proper VGA compatibility:




thanks again for all the info/help darcagn !

 

Whoops, sorry about that, you're right, pin 7 is RGB(S/HV) enable and pin 6 is toggle 15/31khz.

Just as an interesting aside--the way all Katana software (including the BIOS) actually interprets it is 0 pins grounded = composite, 1 pin grounded = 15KHz RGBS, 2 pins grounded = 31KHz RGBHV. Meaning that you can actually reverse pins 6 and 7 and it will still work. I discovered this when I was making a direct DreamcastAV -> Framemeister cable (without a VGA box) and accidentally wired it opposite. All Katana software still worked as intended, but KallistiOS (homebrew SDK) software interpreted it as an invalid video mode when pin 6 was grounded and 7 was floating and displayed a black screen. I submitted a bug report and it's been fixed now, but of course all existing homebrew applications (including all published commercial homebrew) still exhibit this "bug." lol

 

Heh, would you believe that I started looking more into pins 6 and 7 after MNEMO's loader did not display a picture? LOL
You could blindly navigate it and play games just fine, but the menu was not giving any picture.
Is there perhaps more tech/programming info on this so I could pass it to MNEMO ? I imagine it would be nice to have the fix on his menu as well

 

LOL, here's a little bit more background info on it: http://dcemulation.org/phpBB/viewtopic.php?f=29&t=103090

Honestly, I probably wouldn't bother, since it's very unlikely for someone to stumble upon this, but yeah, if you wanna pass that along to him, that's the info. If his menu loader uses KallistiOS, then all he'd have to do is update the version of KallistiOS he's compiling against.