Replacing a GBA SP link port with a DMG link port

Discussion of programming and development for the original Game Boy and Game Boy Color.
Post Reply
User avatar
poorstudenthobbyist
Posts: 222
Joined: Fri Jun 24, 2016 4:20 pm

Replacing a GBA SP link port with a DMG link port

Post by poorstudenthobbyist » Sat Feb 06, 2021 7:37 am

I'm gathering info and parts for hacking a GBA SP into a DMG case. I only plan on using it in GBC mode. One of the things that I want to do that I don't see many others do is keep the outside of the DMG shell as tight and unchanged as possible (partially to make it look as original as possible, but mostly because I don't trust myself to make clean case modifications lol). For example, I plan on using an original power switch and original volume wheel harvested from a broken DMG. Trying to determine if I could somehow route the power jack to the SP battery to recharge it, maybe using a USB to DC jack cable. But that can all be solved after I get all the parts in and I can start tracing out differences between the two boards. The thing I'm trying to figure out right now is the link cable port. I'd really like to use a properly sized link cable port in the DMG case, to keep it as original-looking as possible.

I'm trying to determine if the incompatibility between linking a DMG to other consoles is purely a physical one - that is, it is "incompatible" unless you connect the pinout correctly through a cable, or does said cable have some kind of translation between types of Gameboys? Since the DMG runs at 5V, and the other Gameboys run at 3.3V, I imagine there is some level translation going on, either in the link cable itself, or before the link port (probably the non-DMGs boosting to 5V, since they came after the DMG). The universal link cables seem to have an extra plastic "block" that might house electronics to do this level translation, but I'm unsure if this is simply a wire splice. (I don't have a cable to hack up to check). My main worry is if I use an SP board with a DMG port, and the cable has level translation circuitry inside the black box, it'll translate 3.3V from the SP board with DMG port to something lower, or in reverse, boost 3.3V from a Gameboy hooked up through the cable to 5V and overpower the SP's motherboard.

TL;DR - if I take an EXT connector from a DMG and wire it up properly to an SP circuit board, will I still retain the ability to connect to other gameboys provided I have the right cable?

(I hope I explained this question well enough)
Check out my website for NES, SNES, and Genesis tutorials here. And visit my store for some custom tools and boards for making games here.

You can also follow me on Twitter for infrequent updates and bad jokes!

nocash
Posts: 1326
Joined: Fri Feb 24, 2012 12:09 pm
Contact:

Re: Replacing a GBA SP link port with a DMG link port

Post by nocash » Sat Feb 06, 2021 11:01 am

There is a voltage switch in the cartridge slot. That's all, the voltage just depends on the cartridge. GBA and GBA SP still use 5V in 8bit mode.
homepage - patreon - you can think of a bit as a bottle that is either half full or half empty

User avatar
poorstudenthobbyist
Posts: 222
Joined: Fri Jun 24, 2016 4:20 pm

Re: Replacing a GBA SP link port with a DMG link port

Post by poorstudenthobbyist » Sat Feb 06, 2021 11:56 am

nocash wrote:
Sat Feb 06, 2021 11:01 am
There is a voltage switch in the cartridge slot. That's all, the voltage just depends on the cartridge. GBA and GBA SP still use 5V in 8bit mode.
Seriously? I feel dumb for not finding that earlier haha
So, the output on the serial port will be 5V for GB/GBC games, and 3.3V for GBA games?
(I'm assuming there's a boost converter in the console as well for non-DMG Gameboys, since they run on 2 AA batteries)
Check out my website for NES, SNES, and Genesis tutorials here. And visit my store for some custom tools and boards for making games here.

You can also follow me on Twitter for infrequent updates and bad jokes!

lidnariq
Posts: 10265
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Replacing a GBA SP link port with a DMG link port

Post by lidnariq » Sat Feb 06, 2021 12:27 pm

poorstudenthobbyist wrote:
Sat Feb 06, 2021 11:56 am
(I'm assuming there's a boost converter in the console as well for non-DMG Gameboys, since they run on 2 AA batteries)
Of some sort, yeah. Original DMG has a flyback converter to generate 5V and -18V. GBC service manual shows some kind of DC-DC converter that generates 5V, -15V, and 13.6V. (source: https://gamesx.com/wiki/doku.php?id=sch ... s#nintendo )

The translated GBA service manual (source: https://www.reddit.com/r/Gameboy/commen ... l_english/ ) shows a DC-DC converter additionally generating 2.5V and 3.3V.

User avatar
poorstudenthobbyist
Posts: 222
Joined: Fri Jun 24, 2016 4:20 pm

Re: Replacing a GBA SP link port with a DMG link port

Post by poorstudenthobbyist » Sat Feb 06, 2021 2:53 pm

Oh this is excellent. Thanks.
This'll help when I'm figuring out how to frankenstein some DMG things onto the SP board. Especially the speakers/headphone jack.
Check out my website for NES, SNES, and Genesis tutorials here. And visit my store for some custom tools and boards for making games here.

You can also follow me on Twitter for infrequent updates and bad jokes!

lidnariq
Posts: 10265
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Replacing a GBA SP link port with a DMG link port

Post by lidnariq » Sat Feb 06, 2021 4:03 pm

I don't think we've yet seen a leaked GBASP service manual, so be careful around the things that will have changed.

nocash
Posts: 1326
Joined: Fri Feb 24, 2012 12:09 pm
Contact:

Re: Replacing a GBA SP link port with a DMG link port

Post by nocash » Sat Feb 06, 2021 5:33 pm

Until a few minutes ago, I've had never seen an official service manual or schematic for any nintendo handhelds.
Are there more such documents around? Specs for the BGA chips in NDS and newer consoles would be especially interesting.

Pinouts for GBA and GBA SP are in https://problemkaputt.de/gbatek.htm#externalconnectors for CPU, connectors, other chips, and parts of the SP backlight circuit. It's mostly for digital stuff, with details about analog parts.
homepage - patreon - you can think of a bit as a bottle that is either half full or half empty

Post Reply