αSNES (alphaSNES): A modern, zero-compromise, single-PCB Super Nintendo Entertainment System portable.
After getting I2S audio from the SNES in 2020, I thought it would be a shame to build a SNESp with digital audio, yet settle for composite video, a hand-wired cartridge slot, and all the other old-school aspects of SNES portablizing. Not to mention existing commercial SNES handhelds like the SupaBoy and FC16Go have terrible build quality, crunchy audio, noisy composite video, and are based on 2-Chip clone ICs with poor compatibility. (see nauseating images below)
αSNES Design Goals
Here are the features I'm planning on implementing in the portable:
- Reimplemented 1Chip Super Nintendo
- 1Chip because it offers the highest quality native analog video of any SNES revision (at the expense of some minor visual glitches in games I don't care about.)
- 2Chip does have the potential for lossless video quality via the debug digital video bus, but the additional complexity of the 2Chip and CPLD/FPGA work needed to make it work with an LCD isn't worth the hassle vs the solution I've come up with for the 1Chip.
- Internal SD2SNESflashcart with cartridge multiplexing
- An internal flashcart will allow me to carry the entire SNES library with me on trips, without lugging dozens of carts around.
- With cartridge bus multiplexing, I'll be able to swap between the physical cartridge slot and internal SD2SNES at will, letting me play my physical Super Metroid or Super Mario RPG carts without the hassle of dumping their save files and moving them to the flashcart.
- Integrated GBS8200 with GBS Controlfirmware
- The GBS8200 scaler board (based on Trueview 5725) can linedouble 15kHz RGBs sources and output 480p VGA. With the custom GBS Control firmware by ramapcsx2, the video quality approaches that of high end system like the OSSC but for much cheaper. Scans of the board here.
- 5" 640x480 LCD driven with linedoubled VGA from GBS8200
- (Possibly) integrated LCD driver (may not fit on the PCB lol)
- I2S audio mixed with analog cartridge audio,
- My idea here is to use the LM49350 to mix the SNES's I2S with the cartridge's (and internal flashcart's) analog audio for full compatibility with Super Game Boy and MSU-1 romhacks. We'll see if I can manage it.
- Controls: probably an SN30 Pro d-pad or similar, with regular SNES face buttons. Maybe Switch Pro Controller triggers if I can CAD up the case to fit them.
- Case: Recessed cartridge slot, so the cart is flush on the back of the handheld. Need to make some mockups of this to get a feel for it... Perhaps an all-black color scheme? We'll see.
- Miscellanous: Dual 18650s or lipos, AV out
I did some basic preliminary PCB work a long time ago, but only this month have I actually started working on soldering up and testing the prototype PCBs. I have zero MCAD work done, but I'm hoping the structure of a worklog and the summer contest will help motivate me!!!
Next post: Assembly and testing of the initial prototype PCB design seen above
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