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Hey guys, here's a little thing I've been working on. It's an online tool to create a gameboy rom that has the Nintendo logo replaced with whatever logo you draw! It won't boot on a real gameboy, but it will show the logo you draw as it scrolls down and then hang there. Not super useful but kind of fun!
So check it out at: http://catskull.net/GB-Logo-Generator/
Code is up at: https://github.com/catskull/GB-Logo-Generator
Last edited by catskull (Aug 6, 2016 3:46 pm)
Now we just need someone to produce a cart that can use the classic logo swap trick and quickly remap 0x104-0x133.
Last edited by jefftheworld (Dec 8, 2015 4:19 am)
Now we just need someone to produce a cart that can use the classic logo swap trick and quickly remap 0x104 to 0x133.
Does it really use 0x133? Isn't that where the rom title and other things are stored?
The title sits in 0x134 to 0x143.
OHHHh sorry. I thought you meant remap memory location 0x104 to memory location 0x133. What you meant was remap memory location 0x104 through 0x133 to somewhere else unspecified.
Sorry for the confusion.
Last edited by catskull (Dec 8, 2015 4:22 am)
OHHHh sorry. I thought you meant remap memory location 0x104 to memory location 0x133. What you meant was remap memory location 0x104 through 0x133 to somewhere else unspecified.
Sorry for the confusion.
Yeah, sorry I wasn't clear. That's how some unlicensed games got their own logo to scroll without locking up the Game Boy but as far as I can tell there's no way to do it without special mapper hardware on the cartridge.
catskull wrote:OHHHh sorry. I thought you meant remap memory location 0x104 to memory location 0x133. What you meant was remap memory location 0x104 through 0x133 to somewhere else unspecified.
Sorry for the confusion.
Yeah, sorry I wasn't clear. That's how some unlicensed games got their own logo to scroll without locking up the Game Boy but as far as I can tell there's no way to do it without special mapper hardware on the cartridge.
Yeah my ultimate goal here was to download an .ips patch that could be applied to any rom. That goal died quickly when I realized the logo trick required special hardware. Oh well.
can't get the gb-file to download. I'm on firefox, any idea why?
can't get the gb-file to download. I'm on firefox, any idea why?
Oh dang, I didn't test on FF at all. Or any other browsers besides Chrome for that matter.
It's probably something with the way I'm creating the rom file. That was pretty funky to figure out. I'll do a little testing to try and figure out whats going on, but I can't make any promises.
You can use this on a real Game Boy with nanoloop one by replacing the logo data in the nanoloop update ROM. Logo data are located at 0x8104 in the update ROM (those at 0x0104 are not used).
Last edited by oliver (Dec 9, 2015 2:03 pm)
Firefox is fixed!
Oliver, your hardware does the memory switching? Do you think it would be worthwhile to have functionality where one could upload a rom to the site and have it patch it?
For anyone interested I wrote a blog post about how I made this: http://catskull.net/gameboy-boot-screen-logo.html
Would be nice. I would embed a link to your site on the nanoloop 1 update page so that people could edit the logo prior to updating.
This seems to be a good place to ask. I've noticed nanoloop still works even if the 'hello' logo is scrambled upon boot; does this have any negative effect on the actual software compared to trying to get a perfect logo each time?
It's only a cosmetic issue (unless the logo freezes of course). If it boots up, it's fine.
The controller on the nanoloop cart swaps the logo after a certain period. This period starts when the /reset pin is powered. However, it seems that the /reset signal for the cart is independent from the one that starts the Game Boy CPU: When you turn on the power switch slowly, you get a different timing and better chances for a scrambled logo. It looks like there are separate power contacts for CPU and cart, probably to ensure that cart memory is ready when the CPU starts.
So, for a "perfect logo", it may help to turn on the Game Boy with more verve.
Last edited by oliver (Dec 20, 2015 11:24 pm)
Ah right, thanks for clearing that up! Such interesting little idiosyncrasies..