Ever wanted to play Game Boy games on your NES? Well it is possible via Retrousb NES Retrovision. Sorry, no audio so you will have to hear my fan going because copyright and my NES is not modified for expansion / extension audio. I also forgot to setup the headphone jack to output.
A few things to note:
-No emulation, original DMG hardware CPU B so games are 100 per cent accurate. Triple buffering to prevent screen tearing.
-Graphics are converted to NES format and controller is read fro the NES controller and written to the Game Boy joypad I/O registers.
-Much like the Super Game Boy, palettes can be set although initially. You are limited to 8 sets of 4 palettes using the internal NES 64 palettes limitation. Game Boy graphics are 2-BIT as is the NES, the format is different enough that they still they need to be converted.
-Audio from the Game Boy can be mono mixed and piped through the NES expansion port using the resistor bridge mod and a 10kohm resistor otherwise you will need to use the headphone jack for stereo audio but this is not easily accessible with the original front-loader NES. Instead, you will need to use an angled 3.5 mm to AV Red and White RCA jack-out. You will also require to attach one Game Genie unit and disable the region lockout CIC otherwise the console will sporadically blink and reset. Using two Game Genies is not recommended due to splitting the voltage differential, but it would allow you to use more common headphone out sources as well as the Game Boy EXT serial port for linking to other Game Boys, the Game Boy Printer, etc.
-The ROM is a modified version of the Famicom Wide-Boy.
-Palette selection is done via pressing Up, Down, left or Right buttons on the second player 2 controller.
-Super Game Boy enhancements such as palettes, special borders, SOUND functions, etc do not functions and are not detected because it is running using original Game boy hardware. The NES would not be able to parse that additional code information as it requires SNES hardware to function.
-Game Boy Color extra RAM and palette data will not be detected for the same reasons.
-Also, here are all 4 border configurations; controlled via pressing A, B, Start or Select buttons on the second player 2 controller.
1. DMG NES Retrovision / modified Famicom Wideboy border
2. Black
3. White
4. Extension of palette 1
-Using a Famicom converter and or clone console such as a Dendy it is possible to play Game Boy games on a Famicom console. There may be some limitations depending on the clone console and I've yet to test this on my AV modded Famicom. Videos soon.
Here is my custom palette list:
.db $38,$28,$18,$09 ;GB Kiosk Wideboy palette 1/8
.db $30,$3D,$2D,$1D ;GB MBL Pocket / black and White
.db $2A,$1A,$0B,$0C ;GB DMG Green spinach
.db $37,$27,$16,$03 ;SGB A-1
.db $30,$16,$1A,$1D ;White, Red,Brown, Black (contrasts well with most games; only 8 palettes so I had to make this work right)
.db $1D,$06,$16,$26 ;Virtual Boy
.db $1D,$1C,$28,$30 ;Reverse CGB GBC Game Boy Color Right + B
.db $02,$21,$18,$28 ;Reverse SGB G-1 SolarStriker default; night space lightning works well with many games)
I have left additional pictures and information on my twitter post:
https://twitter.com/nensondubois_/status/1297989261828947971
