Emulation Homebrew Yokoi: Game & Watch / SM5xx Based LCD Handhelds Emulator

SenseiFromClubPenguin · Aug 26, 2026

This is a simple port of the Yokoi emulator for 3DS / Android created by RetroValou that can play most Game & Watch games, clones, and with beta support Tiger LCD handhelds and David & John games (hypothetical modern LCD console with same processor). You need to build an Android based rompack in addition to running the .nro , more info in the README

Also supports flip grips with 90 and 270 degree screen rotation for the dual screen / vertical games. Check it out here: https://github.com/1timewire1/Yokoi_Game_-_Watch_emulator_switch/tree/switch-port

jeferey · Aug 26, 2026

Ohhh amazing!!

SenseiFromClubPenguin · Aug 28, 2026

If every system's games are working aside from the open source David & John games, I created a patch that let's you patch the missing assets into your rompack. Simply copy your current rompack into the folder with this python script and run it. The script will make a backup of the original pack, and produce a new one with the D&J assets included. Once you verify the new pack is good, you can delete the backup. There's more info in its included README

Post automatically merged: Aug 28, 2026

I just pushed a new build, 1.0.1, that adds support for custom segment visibility and background colors (per request)

mathew77 · Aug 29, 2026

@SenseiFromClubPenguin
Thank you for the Switch port!..

Could you please help me a little: when I try to build my own "yokoi_pack_rgds.ykp" file from my very own MAME ROMs, I've got that error:

Code:

python convert_original.py --target rgds

Traceback (most recent call last):
  File "..\CONVERT_ROM\source\generate_games_path.py", line 15, in <module>
    from source.games_path_utils import GameEntry, write_games_path
ModuleNotFoundError: No module named 'source.games_path_utils'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "..\CONVERT_ROM\convert_original.py", line 19, in <module>
    from source.generate_games_path import generate_games_path
  File "..\CONVERT_ROM\source\generate_games_path.py", line 20, in <module>
    from games_path_utils import GameEntry, write_games_path
ModuleNotFoundError: No module named 'games_path_utils'

All the prerequisites (Inkscape, tex3ds, dependencies) are done, MAME rom in .CONVERT_ROM\rom\roms\ folder in a zipped form.

SenseiFromClubPenguin · Aug 29, 2026

mathew77 said:
@SenseiFromClubPenguin
Thank you for the Switch port!..

Could you please help me a little: when I try to build my own "yokoi_pack_rgds.ykp" file from my very own MAME ROMs, I've got that error:

Code:

python convert_original.py --target rgds Traceback (most recent call last): File "..\CONVERT_ROM\source\generate_games_path.py", line 15, in <module> from source.games_path_utils import GameEntry, write_games_path ModuleNotFoundError: No module named 'source.games_path_utils' During handling of the above exception, another exception occurred: Traceback (most recent call last): File "..\CONVERT_ROM\convert_original.py", line 19, in <module> from source.generate_games_path import generate_games_path File "..\CONVERT_ROM\source\generate_games_path.py", line 20, in <module> from games_path_utils import GameEntry, write_games_path ModuleNotFoundError: No module named 'games_path_utils'

All the prerequisites (Inkscape, tex3ds, dependencies) are done, MAME rom in .CONVERT_ROM\rom\roms\ folder in zipped for.

Weird. I can't help a ton until Tuesday, but first I'd try again with the original repo's converter script for Android in case maybe an edit I did trying to fix the David & John games messed something up (if this works, the output will be missing the D&J games assets, but you just need to use the patch attached above after to re-add those if you want them. That patch is confirmed working)

mathew77 · Aug 29, 2026

@SenseiFromClubPenguin
Wow, thank you!.. With the RetroValou's scripts it's all good for now, hooray!..

Here's my screenshots from the Switch with the v1.0.1 (2.3.1 base) version, works good:

..btw In my humble opinion, just in case, a whole process to compile ykp seems a little bit overcomplicated — all the Inkskapes, devkits, pythons, mame archives, zips, tex3ds, necessary artworks, etc etc etc. These games are hella old, and nobody will care if one will attach already pre-compiled DB with all the compatible games at once near the homebrew.
Bu-u-ut it's just my opinion, and nothing more.

SenseiFromClubPenguin · Aug 29, 2026

mathew77 said:
@SenseiFromClubPenguin
Wow thank you!.. With the RetroValou's script it's all good for now, hooray!..

Here's my screenshots from the Switch with the v1.0.1 (2.3.1 base) version, works good:
View attachment 588286 View attachment 588287

In my humble opinion, just in case, a whole process to compile ykp is a little bit overcomplicated, all these Inkskapes, dekits, pythons, mame archives, artworks, etc, these games are hella old, and nobody will care if one will attach already compiled DB with the homebrew. Bu-u-ut it's just my opinion, nothing more.

That's good to hear! I'll have to revert those scripts in my repo when I can. Yeah, I'm not a huge fan of the rompack system either, but I wasn't sure what to change it to so I just kept their system in. If you have a better idea of how to handle it, I could try to adapt to that (also any other feature requests let me know, I'm gonna look into filters next based on a request)

SenseiFromClubPenguin · Friday at 12:04 AM

Version 1.0.2 is out now! The biggest addition is bridging the gap on the Tiger LCD games, adding support for the remaining 41. However, the button mapping was done automatically (which you can see a full list of controls here), so they're marked as experimental and require enabling a separate setting than the current Tiger / D&J games toggle. Other minor settings include adding support for adding a screen gap between screens for any dual screen content to better mimic how they would actually be spaced a part on a real dual screen setup, and the option to hide duplicate / clone titles. I plan to add more game support and features, but would love feedback for the button mappings of these latest additional games.

Check it out here: https://github.com/1timewire1/Yokoi_Game_-_Watch_emulator_switch/releases/tag/1.0.2

mathew77 · Friday at 3:47 PM

@SenseiFromClubPenguin
Thank you for the update!.. Tried some new games, like Sonic 1 and 2, they're starts well but little unplayable for me: the screen flickering, and there's a some mess on a screen.

I guess I'll stick with the good old 'Ball' and 'Octopus' games from Nintendo, they fit incredible well for this SM5** platform. :grog:

SenseiFromClubPenguin · Friday at 11:30 PM

mathew77 said:
@SenseiFromClubPenguin
Thank you for the update!.. Tried some new games, like Sonic 1 and 2, they're starts well but little unplayable for me: the screen flickering, and there's a some mess on a screen.

I guess I'll stick with the good old 'Ball' and 'Octopus' games from Nintendo, they fit incredible well for this SM5** platform.

That's my take as well, at least from a gameplay standpoint :rofl2:

It is a bit weird you ran into issues with Sonic 1 and 2, as those were added as supported in Yokoi prior to me making this port, I'll have to look into it more

Post automatically merged: Saturday at 12:22 AM

v1.0.3 is out, just a minor hotfix (packs created for v1.0.2 will work perfectly with v1.0.3) that fixes the following issues:

Crab Grab and Spitball Sparky segments are no longer rendering as solid blocks instead of intended sprites
Portrait games are now ignored by the screen gap setting (the two above and three David & John Games)
Minor settings text rendering issue where text would clip off-screen if it was too long to display at default font size are fixed

I also went ahead and added a controls list for all the other games, similar to the experimental games list, which you can check out here!

https://github.com/1timewire1/Yokoi_Game_-_Watch_emulator_switch/releases/tag/1.0.3

SenseiFromClubPenguin · 2026-09-17T00:26:32+0100

Version 1.0.4 is out now! Download it here! This is a major release (likely the last 1.0.x version):

Added support for ALL remaining Konami, Tiger, and a few misc. hh_sm510.cpp MAME LCD games to the Experimental category (with 2 currently impossible exceptions, more info below). As with the last batch the controls for these new games are located here (This is especially useful for the non-game devices that were added, as they don't have as clear of a button translation)
Fixed a major bug in processing colorful background art, resulting in a lot of lost detail (the new approach is a bit over-aggressive for Tiger and Konami games, preventing the game background color setting having any effect, but Accuracy > Features)
Added 2 player support for the 3 Micro VS. System games (Boxing, Donkey Kong 3, and Donkey Kong Hockey). Just start Game B with a second controller connected and have fun!
Added automatic time set mode. While time was already correctly synced, with a lot of games they still booted you to the clock set mode. Now the default skips this behavior, starting you at the screensaver time mode instead.
Added new experimental ZL + ZR button modifier system to allow for mapping more inputs (currently used by the calculator games)
Added triple screen support, used by Treasure Island
Fixed an audio bug where audio would die after either being put in sleep mode or playing too many games.
A new experimental SM530 CPU core, built from scratch, used for the Nintendo / Nelsonic Game Watches
Added overlay system used by the Bassmate Computer
Added support for Altair's dosimeter (Geiger counter), though it's currently unknown what function, if any, it has on the dumped ROM.

A few notes: First, the 2 games that are currently impossible to support are Basketbol by Elektronika, which is an LED game that would require a whole new display system, outside of the scope of this project; and Superkubiki ("Super Cubes") also by Elektronika (supposedly only a bad dump exists (I couldn't even find that), with an LCD SVG made "from scratch" based on a low-resolution, blurry infrared photo, so eventually it could be supported if those issues are ever sorted.

For Altair by Nauchpribor, the background is a slightly inaccurate recreation that's being used as a placeholder for the time being. There are only two low-res pictures of the unit, so it's gonna be tricky making a fully accurate version.

What's next:

.ykp pack editor, allowing for adding, removing, or editing individual games to your generated .ykp without needing to regenerate the whole pack
Per-game input mapping, which will double as a way to view controls from within the emulator
McDonald's LCD Sonic games support (via LCDonald)
Further device compatibility exploration
Console frames and filters

Emulation Homebrew Yokoi: Game & Watch / SM5xx Based LCD Handhelds Emulator

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