Dreamcast Sync

[mesmer]

Anyone know about the Dreamcast sync signal? Why does the VGA box schematic require the buffer? Why the resistor to +5 and diode to ground? What is the polarity output?

Seems odd, my Saturn and snes c-sync work straight from the console. I was hoping the Dreamcast would be the same.

Also, gamesx reports that c-sync is disabled in 31khz mode, is this true??

FYI h and v sync are enabled in 15khz mode, I used to have a vga box and did the mod to enable 15khz. Because the vga connector only had h and v sync hooked up, and it worked, then h and v sync must have been on.

It looks like in this schematic they are running c-sync directly, and using 150ohm resistors for h and v sync. It also backs up the claim that c-sync is disabled in 31khz mode, because they use a h+v combiner for that.

I would just go the vga box route again, but they have shot up in price. Also, I need c-sync, and my extron rgb unit died.

[rCadeGaming]

I use a custom cable that just uses the RGBHV straight from the console and little dip switches to set the 15/31kHz selector pins. Works fine for either. Check the first link in my sig.

I don't know about the c sync, as I'm using HV all the time. You could do the same and combine them easily though. Try this:

"you will need to create Composite Sync. This is done by running the Horizontal Sync through a 1N4148 diode and running the Vertical Sync through an 820 ohm resistor then connecting the two lines together (sync mix by viletim!)."

Found here:

http://gamesx.com/wiki/doku.php?id=av:gamecube_rgb

[Endymion]

C-sync does indeed disable in 31KHz mode, so you will need to combine if your monitor requires it.

[HydrogLox]

Also, gamesx reports that c-sync is disabled in 31khz mode, is this true??

Yes, see http://shmups.system11.org/viewtopic.ph ... 82#p869282. There is a discussion about Dreamcast VGA/RGB buried in that topic starting about http://shmups.system11.org/viewtopic.ph ... 63#p867063.

[mesmer]

Ah, thanks for the confirm about c-sync disable. I try to avoid the huge scaler threads =)

I guess I'll get another Extron RGB unit, as I don't want to spend the time building a sync combiner circuit. I can just run everything through it, and not worry about what type of sync each console is outputting.

Now the question, should I get a vgabox, or just make my own custom cable... hmm

I use a custom cable that just uses the RGBHV straight from the console and little dip switches to set the 15/31kHz selector pins. Works fine for either. Check the first link in my sig.

Ah yes, I love your setup. I saw it a while back, just caught up on your newest post.
I see that you leave the caps out of the cables for the RGB lines, even if they are supposed to be in the SCART cable for that console. I saw that you put caps in the switches, so I guess that takes care of it?

So what is the first thing in your setup that receives the HV sync straight from the dreamcast? Your sync circuit in your swith is bypassed, and HV sync is passed directly to your transcoder?

[rCadeGaming]

I don't want to spend the time building a sync combiner circuit.

You can handle a combiner circuit of one diode and one resistor. Especially if you can make your own cables.

Also, are you aware that Extron RGB interfaces can cause a frame of lag? I've proven it with high speed video. Fudoh doesn't think this applies to all models, but I've confirmed it with a 202, a 202xi, and a 202xi w/ ADSP. I wouldn't trust anything to be lag-free that hasn't been tested.

http://forum.arcadecontrols.com/index.p ... msg1318551

Ah yes, I love your setup. I saw it a while back, just caught up on your newest post.

Thanks. It was a bit of work, but it was worth it to be done cable swapping, especially with the Emotia.

I see that you leave the caps out of the cables for the RGB lines, even if they are supposed to be in the SCART cable for that console. I saw that you put caps in the switches, so I guess that takes care of it?

Yes. It doesn't matter where they are, as long as the color lines run through them at some point. In my case, no point in putting a set in each cable when I can just have one set in the switchbox at the end of the chain.

Not every console or source needs them either. Saturn doesn't for example, but it doesn't hurt to use them anyway. The only thing I've seen that's had problems with unnecessary caps on the color lines is the Emotia's output.

So what is the first thing in your setup that receives the HV sync straight from the dreamcast? Your sync circuit in your swith is bypassed, and HV sync is passed directly to your transcoder?

Correct. The sync circuit is only used when activated with 5v from an RGBs or RGB with composite as sync source. RGBHV from the Dreamcast runs straight to the transcoder, aside from the color lines running through the caps.

[mesmer]

Also, are you aware that Extron RGB interfaces can cause a frame of lag? I've proven it with high speed video. Fudoh doesn't think this applies to all models, but I've confirmed it with a 202, a 202xi, and a 202xi w/ ADSP. I wouldn't trust anything to be lag-free that hasn't been tested.
http://forum.arcadecontrols.com/index.p ... msg1318551

Didn't know. I had a 150xi, will probably get that again, or a 160xi. I don't use ADSP (DDSP dip on). You did your test with ADSP on?

[rCadeGaming]

All tested all three of the models I listed and got the same result, 202, 202xi, and 202xi w/ ADSP. Only one model had ADSP. I'd be interested to know if any non-202 models don't have the lag problem.

[Fudoh]

I have the 203 on my Sony LCD and I used Leo's lag tester. Direct HDMI into the Sony and Leo's + HDFury into the Extron - - identical results down to +/-1ms. I really can't do anymore than test it

[rCadeGaming]

Hmm, got any 202's? I'll be getting one of Leo's testers eventually...

[Fudoh]

no, sorry, always tried to stay away from the Extrons with the Barco Din9 connectors.

(Oh, and mine has sync processing on, since I use it for shifting)

[matrigs]

i can just add that i did the mod without the buffers and it works fine.

imho - those buffers are used for switches to disconnect the h-sync and v-sync lines when they are unused.

[mesmer]

Yeah, it makes sense that the buffers are used for their tri-statededness. Anyone know about the rest? I made a terrible diagram:

[matrigs]

those are pull-ups and pull-downs for protection. you'd have to use google though to read upon a bit.