Gameboy Development Forum

Discussion about software development for the old-school Gameboys, ranging from the "Gray brick" to Gameboy Color
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#1 2018-08-12 05:38:18

JS7777
Member
Registered: 2018-07-25
Posts: 17

Boot a Game with ustom boot logo

Hello there,


I actually managed to boot a game with a custom boot logo, since the gameboy reads this part twice, once for VRAM and once to check that it's correct.

So I've used an attiny85 to select the rom with the custom logo then a delay of 100ms then the rom to boot up, it works perfectly on a gameboy and gameboy color

However I couldn't find how to do it for a Gameboy Advance, the delay isn't the same (around 400ms) hence I still can't boot the game with the full custom logo.
https://i.imgur.com/QR89OnK.png

I was wondering if it' possible on a GBA.

Regards

Last edited by JS7777 (2018-08-12 17:30:18)

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#2 2018-08-19 08:38:12

Tauwasser
Member
Registered: 2010-10-23
Posts: 88

Re: Boot a Game with ustom boot logo

Probably the easiest would be if your ATtiny would be fast enough to catch read and write accesses on the Game Boy bus. Then it could just look for the reads from the Logo are and use #RAM_CS to determine if it's Game Boy Color or regular Game Boy.

Do you program different start conditions for Game Boy and Game Boy Color? A simple delay wouldn't work, because both read the logo part and the verification part in a different order.

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#3 2018-08-20 08:33:19

JS7777
Member
Registered: 2018-07-25
Posts: 17

Re: Boot a Game with ustom boot logo

Tauwasser wrote:

Probably the easiest would be if your ATtiny would be fast enough to catch read and write accesses on the Game Boy bus. Then it could just look for the reads from the Logo are and use #RAM_CS to determine if it's Game Boy Color or regular Game Boy.

Do you program different start conditions for Game Boy and Game Boy Color?

Thanks for your reply.

Oh yea, on a gameboy pocket or gameboy I had to start with the custom logo rom instead of the nintendo logo rom and the delay is 500ms.

A simple delay wouldn't work, because both read the logo part and the verification part in a different order.

Well on a gameboy color a simple delay works,  the delay is 100ms.


But the table I've made is for the Gameboy Advance, it got probably another verification method.

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#4 2018-08-23 08:08:09

Tauwasser
Member
Registered: 2010-10-23
Posts: 88

Re: Boot a Game with ustom boot logo

The Game Boy Advance uses a regular Game Boy Color CPU, so the only thing that could be different is the delay from power-on to the actual logo check. You should be able to see if your delay is correct depending on the actual logo that is shown during boot.

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