Hey there!
So yeah, after seeing that this was pretty much possible (thanks to metroidmaniac's effort) and since this was something that I always wanted but nobody came up with, I decided to give it a shot and try it myself. I've been working on this over the past 2-3 weeks and so far it looks half-decent.
The goal is to create a firmware that is nice, easy to use, has some sane defaults and requires no PC (patches included in the FW). Ideally would be fast, have many features, and be easy to update and mess around. And open source of course! (Will be releasing the code soon!) Other cool things are: using Elm's FatFS lib (so support for FAT32 and extFAT is possible), proper font rendering and unicode support (no more ascii-only filenames!), no limits on file count/directory count, can load GB/GBC roms using goombacolor, etc. Let's make this very 2024.
So far this is a pretty much early demo. Supports many commercial games (haven't done almost any testing) with patches for WAITCNT (aka whitescreen) and EEPROM. Working on getting patches for FLASH next. Has no support for flashing, so you need chainload it from another supercard firmware.
WARNING! ACHTUNG! This is pretty much a demo, almost guaranteed to destroy your sav files, if not your SD card! Please stay away if you want something usable.
I'm posting this since I'm gonna be out for a month on vacation so I wanted to say hi and force myself to pick it up and finish it once I'm back.
The obligatory video:
That's it, below here a long explanation for those interested in the details:
I have worked a bit of gpsp over the past years, so I added some minimal supercard emulation on a branch, so I could develop this without having to test on real hardware (it's so much faster to develop this way). That's how the video was recorded. The support is very minimal, and unlikely to publish it, but I thought about adding some support to mgba, since the developers seem open to the idea.
Another cool topic is patching: I've developed some cool emulation/static-analysis based system that can find patching offsets for WAITCNT. I will be writing a post about this soon, since it is a cool idea and can be repurposed for other things. ATM it only works for the Thumb instruction set, working on adding ARM support. The firmware ships a database of patches (~80KB) and uses it to patch games. It also has support to load patches from the SDcard so updates and alternative patch databases can be distributed (without having to flash a new firmware).
And I'm going to bed, I'll post more tomorrow