A8PicoCart - UnoCart on a Raspberry Pi Pico

Hi All, I got a Raspberry pi pico a few weeks ago to have a play with and forgot about it. Then, after noticing a post here, I realised I couldn't resist having a go at using it to make a multicart for the Atari 8-bit. A couple of PCB revisions later, I'm pretty much done, and proud to announce the A8PicoCart! Unfortunately the official Pico board hasn't got quite enough pins to make a proper multicart - you can emulate 8k and 16k carts, but that's about it. However I dis

I have a UnoCart with updated firmware and just like the official last firmware it does not work in Atari 800. So my questions are: 1.- Since A8PicoCart is based on UnoCart firmware, is A8PicoCart also incompatible with Atari 800? 2.- If that is true?, what is needed to make it compatible? Is it the Atari interface part (the menu) that is using calls that only the XL/XE OS has? I am working in a PCB board for the brown Atari case, and therefore, if compatible with the