Hello!
I am designing a videocard to use with Atari with my ABEX Extender https://github.com/gianlucarenzi/abex.
At the moment I have two card already designed: a UnoCart Compatible and an expansion memory up to 1024K (can be more if needed).
https://github.com/gianlucarenzi/abex-megaram for the 1Meg Expansion (it uses the various pokey PORTB expansion bit tables)
https://github.com/gianlucarenzi/abex-duocart for the UnoCart compatible card.

At the moment I am building a virtualization mode for atari800 emulator who is emulating the $D5xx access to have access to a videocard with some basic commands. The processor on the videocard is capable of 320×240@256 colors (palette) @ 50Hz. I was thinking (as the memory on board has 192k) having two framebuffers plus a 32 sprites 32×32 pixels (256 colors shared the palette with the screen). If the screen is not bitmapped, the tile mode can be used. Each tile has to be 80×60 pixels, and up to 16 tiles. In that case the tile can be transferred using 4.8k each, so with a very little cpu access to transfer 224 bytes every transfer. Maybe some scrolling can be made. At the beginning I was thinking to have a sort of V9958 emulation mode because it can have 192K as expansion, but I did not found any valuable example using that card on the 6502… So I opted to have a my personal implementation of the video card.
The processor is a STM32F429I running at 180Mhz with FreeRTOS. Actually it can manage the PHI2, R/W, CCTL, DATA and ADDRESS Lines fairly easily in a task and a second task to manage video output.
If you give me all details used in your library, I can optimize my code to fit the Unity Library… Maybe it can be done almost easily.

My personal email is: icjtqr@gmail or gianlucarenzi@eurek.it (job)

Please let me know,
Regards,
Gianluca

At the moment
The biggest issue is the transfer of the video data (sprites, backgrounds) in a very small window (224 bytes each transfer).