Shark MX GameBoy Modem!

Discussion of programming and development for the original Game Boy and Game Boy Color.
User avatar
uXe
Posts: 27
Joined: Sun Nov 25, 2012 5:28 am
Location: Adelaide, Australia

Shark MX GameBoy Modem!

Post by uXe »

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"
User avatar
Kasumi
Posts: 1293
Joined: Wed Apr 02, 2008 2:09 pm

Re: Shark MX GameBoy Modem!

Post by Kasumi »

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.
User avatar
blargg
Posts: 3715
Joined: Mon Sep 27, 2004 8:33 am
Location: Central Texas, USA
Contact:

Re: Shark MX GameBoy Modem!

Post by blargg »

$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
Posts: 775
Joined: Mon Jul 02, 2012 7:46 am

Re: Shark MX GameBoy Modem!

Post by qwertymodo »

Eh, what the heck. Why not. Could be interesting.
qwertymodo
Posts: 775
Joined: Mon Jul 02, 2012 7:46 am

Re: Shark MX GameBoy Modem!

Post by qwertymodo »

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.
User avatar
Dwedit
Posts: 4922
Joined: Fri Nov 19, 2004 7:35 pm
Contact:

Re: Shark MX GameBoy Modem!

Post by Dwedit »

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
Posts: 22705
Joined: Sun Sep 19, 2004 11:12 pm
Location: NE Indiana, USA (NTSC)
Contact:

Re: Shark MX GameBoy Modem!

Post by tepples »

And the timing for replacing the logo differs on the Game Boy, the Super Game Boy, and the Game Boy Color.
User avatar
MottZilla
Posts: 2837
Joined: Wed Dec 06, 2006 8:18 pm

Re: Shark MX GameBoy Modem!

Post by MottZilla »

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
Posts: 1
Joined: Wed Mar 19, 2014 7:51 am

Re: Shark MX GameBoy Modem!

Post by gameshark-mx »

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
User avatar
B00daW
Posts: 586
Joined: Thu Jan 03, 2008 1:48 pm

Re: Shark MX GameBoy Modem!

Post by B00daW »

Remarkable job. Thanks.
BennVenn
Posts: 107
Joined: Sat Mar 29, 2014 10:01 pm
Location: Australia
Contact:

Re: Shark MX GameBoy Modem!

Post by BennVenn »

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
Posts: 11430
Joined: Sun Apr 13, 2008 11:12 am

Re: Shark MX GameBoy Modem!

Post by lidnariq »

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...
BennVenn
Posts: 107
Joined: Sat Mar 29, 2014 10:01 pm
Location: Australia
Contact:

Re: Shark MX GameBoy Modem!

Post by BennVenn »

Hi lidnariq,
I've mapped out a few registers. Check www.bennvenn.com/Datel_MBC1.htm for info.
Ben
lidnariq
Posts: 11430
Joined: Sun Apr 13, 2008 11:12 am

Re: Shark MX GameBoy Modem!

Post by lidnariq »

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?
BennVenn
Posts: 107
Joined: Sat Mar 29, 2014 10:01 pm
Location: Australia
Contact:

Re: Shark MX GameBoy Modem!

Post by BennVenn »

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?
Post Reply