Bizarre VGA Problem

OldFoo · Post by **OldFoo** » Mon Feb 26, 2007 11:37 pm

So I have this strange problem when running my Naomi to my VGA LCD monitor. The monitor only seems to recognize the Naomi's VGA signal on certain occasions. For instance, if Ikaruga is running the monitor will always recognize and correctly display the signal. However, most other games fail to send any resolution information at all, and the display defaults to whatever resolution it was at before. Since my computer is also hooked up to this monitor via DVI, it usually defaults to 1280x1024. This results in my having to set my computer's resolution to 640x480 and then switch the input from DVI to VGA. Needless to say, this is a pain, and I really can't be arsed to do it every time.

My Atomiswave, doesn't have this problem--it sends the right info each time, as long as the dipswitch is set. I now have the Atomiswave and Naomi both hooked up to the VGA input of my LCD monitor via a switchbox. So I can turn on the Atomiswave and then flip the switch to the Naomi's input and it works OK. Unfortunately, this puts needless wear and tear on the Atomiswave by switching it on/off all the time. What makes it weird is that once it's given the proper resolution, the LCD will then read the proper timing and refresh of the Naomi. I really don't know what's going on. :smt017

I suppose what I need is some sort of device that always sends the proper resolution and timing info connected to the VGA port. Does anyone know of such a product? If not, does anyone know how to build one? This is really a pain, so I'd appreciate any help at all.

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 3:51 am

This could be a power issue (not enough). What type of psu are you using for the Naomi?

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 5:05 am

joshua3dg wrote:This could be a power issue (not enough). What type of psu are you using for the Naomi?

I don't think so. I'm using a 250 watt ATX PSU. There aren't any other video issues whatsoever. As soon as it gets the proper rate, it syncs up. It seems more like the software enables a flag to send the proper info or something. I actually get a picture if I don't correct the resolution--it is just doubled. You'll know what I'm talking about if you ever have the dip set to 31kHz, but are still viewing the picture on a lo-res RGB monitor--same result here.

I don't think it's a fault in the hardware, since the results are entirely consistent. There is something in the Ikaruga software that tells the monitor the proper resolution and sync.

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 5:37 am

It only happens with the one game? :smt017 That's pretty weird. I also use an LCD monitor with my Naomi, but I don't have this game so I can't say whether it's the game or not. But I don't think that any Naomi game actively communicates the VGA output like a computer does. The system doesn't need to identify the monitor because it only outputs to one VGA resolution.

Are you using any video converters? If so, it could be a sync issue with a inline converter. I mention this because there was a discussion about this a while ago about how different systems might scale the video differently (old news :smt015 ).

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 5:51 am

Actually, it's the only one I can remember off of the top of my head. I'd have to go back and try the others, but I can tell you that it doesn't work for GGXX #Reload or Melty Blood AC.

I'm not using any converters. I know that the Naomi system doesn't need to identify the monitor, but perhaps the monitor needs to identify the Naomi. The only thing I can think to compare it to is how the Dreamcast actually requires a flag in the software to enable the game to display in VGA. Maybe this is something similar?

I'll have to do a few more tests to isolate a few other possibilities.

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 1:05 pm

I have to use the auot-adjust feature of my plasma when using my Naomi. Then it seems to remember it the next time.

It does vary from game to game I've noticed.

OldFoo · Post by **OldFoo** » Tue Feb 27, 2007 5:36 pm

This is really driving me crazy! :smt011 I checked out a couple of other games, and same result.

I also tried disconnecting the computer, unplugging the monitor and replugging it back in--nothing. It wouldn't recognize the Naomi signal. However, once I switched over to the Atomiswave, the monitor synced up fine. From then on it remembered the 640x480 resolution and saw the Naomi on power-up, even when the monitor had been turned off (as long as it hadn't been unplugged). It would seem that the monitor keeps the last known resolution in memory and uses that as the default unless it senses a new one. The question remains, however, how do I get it to recognize the Naomi on its own?

Jeff Kurtz suggested I take the video signal from the JAMMA edge and build a sync separator circuit for it, but he said that was only a guess.

@Joshua - How do you have the VGA cable hooked up? Is it running from the JAMMA edge of the I/O, or from the mainboard? Any other thoughts?

@dj_johnnyg - The auto-adjust doesn't help me on mine.

Also, does anyone know if the pinout on the mainboard is exactly the same as standard VGA?

Help...

OldFoo · Post by **OldFoo** » Wed Feb 28, 2007 3:22 am

brumma wrote:Also, does anyone know if the pinout on the mainboard is exactly the same as standard VGA?

It is exactly as VGA. I also have Melty Blood and it works fine with my LCD monitor. At least we have a game in common to diagnose with. I connect the Naomi straight from the filter board to the LCD VGA connector. You can't really use the Jamma edge when using high res and RGB(low res) is not accepted by most monitors.

Here's something to try: Some monitors have a setting for the line voltage for the video feed. There's usually 2 settings and is identified by the "0.xV p-p"or Volts Peak-to-Peak. If your LCD has this setting, try the other.

The only other option is to use another monitor.:smt024 Or, perhaps, another Naomi.

OldFoo · Post by **OldFoo** » Wed Feb 28, 2007 4:46 am

joshua3dg wrote:
brumma wrote:Also, does anyone know if the pinout on the mainboard is exactly the same as standard VGA?
Here's something to try: Some monitors have a setting for the line voltage for the video feed. There's usually 2 settings and is identified by the "0.xV p-p"or Volts Peak-to-Peak. If your LCD has this setting, try the other.

Where would this setting be? In the menu structure, or is it a physical switch? My LCD is also a computer monitor, not a NTSC monitor (if that matters).

One other thing I've noticed, is that the Naomi usually outputs at a vertical frequency of 59.7Hz, while the Atomiswave is usually 59.9 or 60.0. The exception is Ikaruga, which always seems to output right at 60hz. I think that this might have something to do with the vertical sync. Perhaps the Naomi is just out of range with what the monitor likes, but when told to use 640x480 and 31kHz horz./60Hz vert. refresh by another device it is able to recognize the Naomi's signal as close enough. I always end up having to hit the auto adjust in order to center it and fill the screen, which indicates that the timing is indeed different from the Atomiswave.

I've actually been looking into either an external RGB interface or a test signal generator as a possible solution. The signal generator wouldn't solve the problem, but it would save the wear and tear on the Atomiswave.

OldFoo · Post by **OldFoo** » Wed Feb 28, 2007 5:06 am

The setting would be in the menus. I think your LCD is just being picky about the video signals. I know you may not want to, but a different monitor would be the best fix for this problem.