Shark MX GameBoy Modem!

Discussion of programming and development for the original Game Boy and Game Boy Color.
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uXe
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Shark MX GameBoy Modem!

Post by uXe » Sun Nov 25, 2012 5:40 am

This turned up over on chipmusic.org - an eBay seller has 4,285 of these for sale at $5.95 each:

http://www.ebay.com/itm/370549655915

...found some more information, and it looks like the cart is reprogrammable:

http://www.oocities.org/grinara/

I think it would be fun to have a simple dial-up terminal on there, a possible starting point might be:

http://ewen.mcneill.gen.nz/programs/cpc/ansiterm/

Apparently the cart requires activation before it will do anything making it fairly useless without any modification:

"For those of you considering the purchase of a Shark MX, be advised that since the sale of Gameshark (from Interact to Madcatz), there is no longer any support for this device, nor the proprietary email service (Gameshark BBS). The toll free# on the 30min activation card has been disconnected, and Madcatz has been of little assistance. (Apparently Madcatz only purchased the website and software rights to Gameshark, and not the "technology" portion.)

Without the MX cart first being "activated" with a factory issued REG CODE (via toll free#), the cart will not function at all, rendering it completely useless. I find it odd that Interact would have locked up the entire cart in this manner, as the PDA functions are not in any way linked to the email functions (ie, address book not linked to email composer).

If you're a collector of odds/ends GB carts, it would be a unique buy. It is a cool gizmo. Don't plan on any serious usage of the device though. Good luck with your purchase. 7/2003"

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Kasumi
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Re: Shark MX GameBoy Modem!

Post by Kasumi » Sun Nov 25, 2012 7:05 am

Wow. Kind of a blast from the past. I wanted one of these when I was young and this was actually in stores. My parents thought it was silly. Of course they were right. :lol: I could get one for nostalgia's sake... but if it's totally locked even for offline stuff, and I have to go through trouble to get around this I may have to pass. Even for six dollars.

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blargg
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Re: Shark MX GameBoy Modem!

Post by blargg » Sun Nov 25, 2012 12:15 pm

$6 shipped even. Who's to say someone won't RE it and figure out how to activate it and perhaps reprogram the cart for other useful things?

qwertymodo
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Re: Shark MX GameBoy Modem!

Post by qwertymodo » Mon Nov 26, 2012 11:53 am

Eh, what the heck. Why not. Could be interesting.

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Re: Shark MX GameBoy Modem!

Post by qwertymodo » Wed Nov 28, 2012 12:32 am

I'm really interested by the fact that it is able to replace the Nintendo logo at boot time with its own logo. I thought that was impossible because the GB wouldn't boot without the correct logo in the ROM header. That's definitely something I'll have to look into when I get mine.

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Dwedit
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Re: Shark MX GameBoy Modem!

Post by Dwedit » Wed Nov 28, 2012 1:26 am

The DMG bootrom verifies the logo after it loads it. So if you are watching the address lines, you can switch the data after it has been read the first time.
See the DMG bootrom disassembly, you can see how it loads it before it verifies it.
Here come the fortune cookies! Here come the fortune cookies! They're wearing paper hats!

tepples
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Re: Shark MX GameBoy Modem!

Post by tepples » Wed Nov 28, 2012 6:17 am

And the timing for replacing the logo differs on the Game Boy, the Super Game Boy, and the Game Boy Color.

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MottZilla
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Re: Shark MX GameBoy Modem!

Post by MottZilla » Thu Nov 29, 2012 12:00 pm

I hadn't heard about Super GB being mentioned in any incompatibility with the Logo Hacks, but I had heard that they don't work on the CGB due to the different process of reading. I do remember reading that the Super GB checks the header checksum and possibly the logo on the SNES side rather than the GB side.

gameshark-mx
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Re: Shark MX GameBoy Modem!

Post by gameshark-mx » Wed Mar 19, 2014 7:59 am

Sorry for necro-posting but thought this would be of some use to someone...

http://gameshark-mx.blogspot.com.au/

It seems someone has cracked the Gameshark Mx email cart registration code and has even made a code generator for it!
Links to a hacked ROM and code generator are supposedly coming soon

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B00daW
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Re: Shark MX GameBoy Modem!

Post by B00daW » Fri Mar 28, 2014 1:44 pm

Remarkable job. Thanks.

BennVenn
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Re: Shark MX GameBoy Modem!

Post by BennVenn » Sat Mar 29, 2014 10:23 pm

Hi there!

So it turns out, the MX card although old, and arguably useless, IS reprogrammable and DOES contain a primitive uart (serial port)

So if you've been after that cheap ($10) flash cart (256kbyte) with a serial port for MIDI?? grab yourself one from Ebay NOW!

It seems the only people still interested in flash carts are those wanting to turn the gameboy into a synth, and they seem to want a midi interface. It has no SRAM but it is a flash cart! so you can write to the flash in operation. No battery issues. Anyway, Take a look at http://www.bennvenn.com/mx.html if you're interested in how it works.

Ben

lidnariq
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Re: Shark MX GameBoy Modem!

Post by lidnariq » Sun Mar 30, 2014 1:24 am

Do we have a full set of registers in the Datel MBC? At the very least, we know there's a UART and a bank control register...

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Re: Shark MX GameBoy Modem!

Post by BennVenn » Sat Apr 05, 2014 3:51 am

Hi lidnariq,
I've mapped out a few registers. Check www.bennvenn.com/Datel_MBC1.htm for info.
Ben

lidnariq
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Re: Shark MX GameBoy Modem!

Post by lidnariq » Sat Apr 05, 2014 11:23 am

Nifty.

It's fascinating that the Si2400's power line (pin 4) is switchable by the MBC: I wouldn't have thought that powering the modem would have been a big enough amount of power. I guess it's easier to just depower it rather than bothering to write ATSxx=yy to the serial port.

Any idea why Cart D7 is disconnected from Flash D7? (Flash programming?) Are Flash D0..D6 directly connected to Cart D0..D6?

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Re: Shark MX GameBoy Modem!

Post by BennVenn » Wed Apr 16, 2014 5:19 pm

Cart D7 is connected to Flash D7. I must have made a typo writing that up. All 8 data lines go into the MBC. Thinking about it, it must have internal ROM too, as it feeds the gameboy a correct logo during its bootrom checksum then switches out the custom logo. I wonder what triggers the logo swapping. maybe a certain number of clock cycles on the clk pin?? Unless the real logo is located in the flash elsewhere and it just bankswitches automatically?

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