Gameboy core

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Mills
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Re: Gameboy core

Postby Mills » Fri Nov 29, 2019 11:16 am

Hi, I was going to post this on github, but I think it is good to post here.

I tested a lot of games and demos, and the core is replicating everything like a real game boy :D , even sprite flickering (and some dma transfer flicker I saw in a demo I made).

But I noticed bugs in some demos and games that use scanline interrupts, it looks like it is not fast enough or something.

For example prehistorik man uses scanline interrupts to simulate parallax and some cool effects. This game runs with a lot of gfx missing in menu, and starting a new game shows just a black screen.

Also tested demos like GEJMBOJ, and the scanline effects are also missing.

A lot of game boy color games and demos use scanline interrupts to draw "highcolour" images (rayman, cannon fodder), or to change palette every scanline... and all of this is also showing gfx errors.

Thanks!

brNX
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Re: Gameboy core

Postby brNX » Fri Nov 29, 2019 2:51 pm

hernan43 wrote:What would cause the Gameboy core to not provide audio over HDMI? Right now all my cores are providing audio over HDMI except the Gameboy core. If I plug headphones into the line out on the IO board it does provide audio just fine. For some reason it does not want to provide audio over HDMI.

Now if I hook it up to a different HDMI display the audio works fine. So it is 100% an issue with the particular display I am using. I am just curious what the difference would be.

~
Mills wrote:Hi, I was going to post this on github, but I think it is good to post here.

I tested a lot of games and demos, and the core is replicating everything like a real game boy :D , even sprite flickering (and some dma transfer flicker I saw in a demo I made).

But I noticed bugs in some demos and games that use scanline interrupts, it looks like it is not fast enough or something.

For example prehistorik man uses scanline interrupts to simulate parallax and some cool effects. This game runs with a lot of gfx missing in menu, and starting a new game shows just a black screen.

Also tested demos like GEJMBOJ, and the scanline effects are also missing.

A lot of game boy color games and demos use scanline interrupts to draw "highcolour" images (rayman, cannon fodder), or to change palette every scanline... and all of this is also showing gfx errors.

Thanks!


Hi
sorry for the radio silence for a while, I've been very busy with life and will continue to be for some time unfortunately , sorry again.
@hernan43 I have the same issues with my TV over hdmi, my guess is that the sound output is missing a filter (LPF/HPF) so that the sound is in HDMI spec , some TVs don't care other don't like it at all.

@Mills yeah it's in my issues list on github, there are other things amiss with the PPU implementation, that one needs to be rewritten probably , I started to compare it in simulation with Sameboy but never got the time to finish it , different codepaths should also be added as the GBC PPU acts differently in a lot of places than the GB one (and of course Furrtek's recent work could be added/used).

crocky
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Re: Gameboy core

Postby crocky » Tue Dec 03, 2019 6:10 am

brNX, thanks for the wonderful Gameboy core, with the LCD filters, its amazing!

I found that on R-Type II with the laser shot, the lasers dont show up on the front of the aircraft but on behind and yet the enemies get hit and die on front. I tried with filters off etc, still the same. Just letting you know in case this was not a known issue. :)

12characters
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Re: Gameboy core

Postby 12characters » Sat Jan 11, 2020 7:03 pm

I am curious about the format of the palettes (.gbp). A hex dump of DMG.gbp gives:

Code: Select all

82 82 14 51 73 56 30 5a 5f 1a 3b 49 00 00 00 00

I recognise the first 12 bytes as the 4 colours of the palette, but what is the purpose of the 4 zero bytes at the end?

12characters
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Re: Gameboy core

Postby 12characters » Sun Jan 12, 2020 7:43 pm

12characters wrote:I am curious about the format of the palettes (.gbp). A hex dump of DMG.gbp gives:

Code: Select all

82 82 14 51 73 56 30 5a 5f 1a 3b 49 00 00 00 00

I recognise the first 12 bytes as the 4 colours of the palette, but what is the purpose of the 4 zero bytes at the end?


I found the answer in gbpalette.c:

Code: Select all

// GBP file format is simple. There are 4 palette colors using 8 bit
// rgb, starting from lightest ending in darkest for a total of 12 bytes.
// The last several bytes are 0, reserved for future use.

In case it is of use for anyone, I have converted some extra palettes to the format:
The GBP files can be found in the attached ZIP archive.
You do not have the required permissions to view the files attached to this post.

trashuncle
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Re: Gameboy core

Postby trashuncle » Fri Jan 17, 2020 8:45 am

Megaman Extreme doesn't work properly. I believe this has already been reported. Any progress on this (or at least a reason as to why this rom behaves this way?)

peepsalot
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Re: Gameboy core

Postby peepsalot » Tue Jan 21, 2020 7:55 am

I've found that the GBC game "Project S-11" has glitched graphics around the title screen and in some of in-game sprites. Not sure if this is a issue with the core itself, or could it be a bug due to the "sameboy" bios?

Piacenti
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Re: Gameboy core

Postby Piacenti » Tue Jan 21, 2020 8:38 am

peepsalot wrote:I've found that the GBC game "Project S-11" has glitched graphics around the title screen and in some of in-game sprites. Not sure if this is a issue with the core itself, or could it be a bug due to the "sameboy" bios?


I get these glitches on Aladdin and Aliens also, not sure what the problem is.

peepsalot
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Re: Gameboy core

Postby peepsalot » Wed Jan 22, 2020 4:15 am

After reading back in this thread a little bit, I think its probably just more examples of the scanline interrupt issues that Mills already brought up at the top of this page.


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