RedtroMedleyCard Business Card Emulator
This business card-sized emulator can’t quite run DOOM but still has a few tricks up its sleeve.
As outlined here, for the last month or so Eontronics has been working on a big-screen compatible retro emulator built around the business card form factor. While the resulting build can’t quite run DOOM (yet) as originally intended, it can run a Game Boy emulator, tested with Dobert Doman’s Space Crawler demo. It also features a rather unique PCB design, which integrates connectors into the board itself.
Processing-wise, the heart of this PCB business card is an ESP32-S3FH4R2, which provides emulation as well as an HID interface – currently limited to HID keyboards. The device employs an RP2040 chip as a video co-processor, outputting visuals over HDMI. No external memory is implemented for the RP2040, and instructions are loaded into the RP2040s RAM via the ESP32.
Eontronics notes that the ESP32-S3 chip itself has only 2MB of PSRAM, While this is a good amount in microcontroller terms, is only enough to run a Game Boy emulator. Anything more leads to a system panic, which dooms attempts to run... DOOM and the like.
DOOM or no DOOM, where this project really shines – in my humble opinion – is its innovative use of PCB elements to form connections. The HDMI connector plugs directly into the main .8mm board, while USB-C connectors hook up via soldered-on .6mm thickness sub-boards. The SD card is even attached via a series of flexible PCB fingers that clamp down on the connection, and a 3.5mm audio “socket” works in much the same way. Sound output, however, is currently a work in progress.
The result is a total board thickness of 1.7mm with nothing attached. Design files can be found here. Although you might not want to duplicate this particular design, it could certainly inspire your next build!