Worklog Egg Boy Color

[leggomyfroggo]

Hey all! I'm back for a second year, and intend to finish this time -- as a matter of fact, I've already made it farther than last year by posting a thread.

Setting the Stage
You may know me from my prior projects where I made custom form factor Game Boy Colors using original hardware:

1. Frog Boy Color: full size, mostly fully featured, wide Game Boy Color -- serious business
2. Tad Boy Color: small, while still using OG cartridges, most features preserved
3. Time Frog Color: stupid side quest -- Game Boy Color in a watch, including tiny custom cartridges -- completely impractical

The Idea
As my GBC mods continue to get smaller, and I approach the minimum possible size with the TFC, I think it's time to round out my ever shrinking amphibian themed family with the smallest practically usable GBC I can imagine. And so, I'm Introducing the Egg Boy Color: the answer to the question, "what if Benjamin Button, but Game Boy?"

Key Features

• Built using original Game Boy Color CPU and RAM for compatibility with original software
• Compatibility with the same tiny cartridges I designed for the TFC
• Audio output via speaker
• Custom tiny buttons
• Small enough to reasonably fit on a keychain

Stretch Goals

• Magnetic charging dock using pogo connections
• Link port support over aforementioned pogo connections

Worklog
For ease of reading, I will post a summary of worklog entries in this main post in addition to more fleshed out ones as separate posts.

5/23/2026
Project kickoff! Started working on the main shell design, both front and back. Front shell is designed around a 1.54" 320x320 IPS screen so I can get a clean 2x upscale on the GBC video.

 

[HERO]

I love your work! I plan on getting a Tad Boy Color very soon. I’d like to make one but I’m gona have to get it commissioned. Could you recommend anyone?

 

[leggomyfroggo]

Got started on the Egg Boy Color electronics this past weekend by designing an RP2040 development board for the main LCD candidate that I'm considering for this project.

LCD Info

Model: ET015SQ05
Size: 1.54"
Resolution: 320x320x16bpp
Interface: SPI, ST7789U driver

I've also attached the datasheet for this LCD so you don't have to email them like I did.

The units I have appear to have been manufactured in late 2019, which I'm hoping isn't a bad sign for future availability. At the very least, I've found multiple Chinese sellers using what looks like the same panel with slightly different flex bridges. I'll be sampling some of those to determine compatibility. Fingers crossed, since this resolution at this size doesn't seem to be widely available, outside of some MIPI panels.

LCD Dev Board

The LCD dev board is an RP2040 carrier board -- based off of the minimal circuit implementation from the RP2040 datasheet -- that is purpose built to test both the screen driver circuitry, as well as the firmware for translating the GBC video signal to SPI for the new LCD.

On the back of the board is a 50-pin FFC socket that connects to a standard Game Boy Color. The video signals from the GBC -- pixel data, pixel clock, H-sync, and V-sync -- are routed to GPIO on the RP2040 through this connector. 3.3V is also carried over the connector to allow the dev board to be powered by the GBC.

The other connector on the back is the 24-pin mezzanine connector that the LCD will plug into. This was actually one of the trickiest parts of the design, as the LCD appears to use an obsolete connector, the OK-22M024-04. It's a 0.4mm pitch 24-pin male connector with a stack height of 0.7-0.9mm. I was unable to find stock of the equivalent female part anywhere, so I had to take measurements and dig through datasheets for similar parts.

After some trial and error, I'm now fairly certain it's a clone of a KYOCERA AVX part. Test fits show it mates well with the 245804024000829+ female connector, so unless I discover later that the pins actually don't connect quite right -- not going to know that until I have the dev board and start powering things up -- that mystery appears to be solved.

The only other interesting parts on the board are LDOs for 2.8V and 1.8V rails. These are required by the LCD, at least according to the datasheet which is somewhat vague on exactly what this thing wants. The SPI lines appear to be 3.3V tolerant according to the datasheet, so I assume there's some level shifting happening internal.

What's Next?

I've ordered the dev boards, so I expect those to arrive in the next couple weeks, and then I can assemble and start testing things out.

In the meantime, I think next I'll start refining the EBC shell, specifically focusing on the buttons since they're still in a bit of a rough shape.

 

[Legend]

After seeing your other projects, im suitably hyped for this one! Good luck and God speed!

 

[MegamindSquared]

Looks awesome!