After assembling several boards, I discovered one thing. The cartridge connection does not fit snugly with the Virtual Boy.
If the connection was slightly loose or too tight, the game would not be recognized properly.

At first, I thought it was a ROM issue, but after covering the ROM socket and swapping out the ROM, I confirmed that it was a problem with the cartridge connector.

It seems that among the many boards you assembled, there aren’t many with the “correct” connectors. I sincerely apologize, but in my opinion, the connector issue is the most severe.

If I could obtain a connector made specifically for the Virtual Boy, I think this problem would be solved, but it is unfortunate that, unlike other game consoles, they are not mass-produced in China.

Once again, I apologize. : (

I placed nuts on the opposite side when tightening!
Since there’s no space for screw heads on the front, the design is based on countersunk screws — so regular screw heads might not fit well. I used M3 5mm screws.

For smaller ROMs, you can just copy them 4 times to fill the size, and for larger ROMs, it seems you can just cut them in half (though I haven’t fully tested that yet).

Sorry if I released this build too early in such an incomplete state.
I really hope it works well for you!

@abarth Sorry for the late reply! I’ve been super busy lately and just haven’t had the time. From the looks of the photo, it seems like the save data is being preserved, but after actually checking it, I noticed the crash issue. It seems like, as mellott124 mentioned, the FRAM might not be fully compatible. I think I’ll need to look for another chip. I’m really sorry about that. 🙁

That said, the FRAM is in the correct spot. From my experience, it works best when it’s tightly connected to the Virtual Boy.

Sorry again for the late reply, and I think I need to test the save function again.

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Thank you! I need to correct FRAM typo.
I’ve just tested Wario land, and the FRAM was working his job.
And if you want to write an 8Mbit ROM, simply copy and paste it once to double its size.
(Do not pad the remaining 8Mbit with 0xFF)

Thanks for taking an interest.

Oh, yes. the PCB and printed shell sizes are slightly different.
That’s because the PCB follows the original Virtual Boy cartridge board size.

But don’t worry
The screw holes line up properly with the 3D-printed case,
so it still fits and works fine.
(Just in case, I forgot to leave clearance around the nut and screw hole area on the PCB, so it’s best to tighten the screws gently to avoid damaging the surrounding traces.)

As for ROM issues:
Honestly, I probably messed up the ROM splitting and padding, so I’m not 100% sure what’s wrong : (
In my case, I just split and padded the ROM using HxD Editor, which is pretty easy to use.

Also, keep in mind that SRAM (or something similar) is required for saving.
EPROM alone can’t save data.

I used FRAM (not SRAM! — because I hate using batteries to save data), but you can also use NvSRAM or similar chips. they should work fine.

I’m planning to retest those 32Mbit ROMs this week,
so hopefully I can figure out what’s causing the remaining issues!
Thanks!

Yes, those connectors are directly solderable,
and they work without any modifications (except for sanding them slightly to fit the Virtual Boy slot)

I also recommend using the shell I uploaded on GitHub,
as it makes insertion much easier. (See the photo for reference.)

About Known issues, I suspect the issue might be with my EPROMs were Bad.
Some games didn’t work, and although I’m not entirely sure why,
it might be related to how I resized them to fit into a 16Mbit EPROM.
(For example, Bound High was originally 16Mbit, while Jack Bros was only 8Mbit. So I just padded the remaining 8Mbit with 0xFF when flashing Jack Bros.)

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That’s right!
You need to use Pitch 2mm 2x30p connector, and may need to sand it a bit.

The 64/128Mbit labels refer to extra pin connectors that I reserved for possible future ROM board expansion.

Currently, the design supports up to 32Mbit EPROM, but once I finish more testing,
I plan to either release a daughter board (…), or a dedicated 128Mbit cartridge design!