In doing research on the Powerpad, it's made me interested in all kinds of AT (Assistive Technology) stuff and I've been reading up on the Adaptive Firmware Card for the Apple II. https://resna.stanford.edu/TopTen/index.htm#1
In this interview they talk a little bit about the Firmware Card at: http://www.inclusive.co.uk/lib/downloads/adaptive-firmware-card.pdf
PAUL: We... [mingled voices]. Yeah, basically it... it was becoming clear to us, and I think at the time it was becoming clear to everybody, uh, and Gregg Vanderheiden, uh, I remember would talk about this very eloquently, that we needed a way to do transparent access to computers, so that we weren’t just running programs that we’d written for special needs but... but that you could run the... that Kris or Steve could run a computer just like anybody else, and they could do anything with a computer. And at that... at that point in time, um, I remember Gregg was espousing an idea of nested computers -- that you would have two computers, and that one computer would run the special-input routine, um, that was, you know, one or two switches, and it would then send its results to the other computer as if you were using the keyboard.
Um, at the same time, I had been doing a lot of adapting programs, and... and I could... I saw that there were advantages to being able to stay within the... the one computer and to be able to have the routine running alongside the program you were adapting, so that it could use the same display and make use of the same resources -- um, sound and the... and if you had an Echo speech synthesizer it could do that.
And so I began thinking about this problem, and I was trying to find a way to combine these two things: to have transparency but also be able to, um,... to make it seem like you’re just adapting the program that you’re running. And ultimately what I came up with was the Adaptive Firmware Card.
Uh, in effect what the Adaptive Firmware Card did was it sort of turned the Apple II, which was a... a single-tasking machine -- you could only run one program at a time -- it sort of turned it into a multi-tasking machine. It was sort of a poor man’s version of a multi-tasking machine, because you might say it was a double-tasking machine -- you... you could run the program plus the input routine as the second routine -- but it was a circuit board that went in the computer, and the adaptive routine that you wanted to run resided on the... on the card, and the hardware played tricks so that when you wanted to use that routine it would interrupt the... the program that was running, and then it would bring up a scanning array or do Morse code or do whatever was necessary, uh, to allow you to generate text with one or two switches. And that was, um,... and I guess that was... that was something new. And ... and I remember, I don’t know how, but somehow Gregg Vanderheiden found out about this. I can’t remember... I might’ve written a letter to the Trace Center, uh, or there was a contest about that time at Johns Hopkins..
There's a great article in the 1982 Byte with all kinds of technical details and schematics:https://archive.org/details/byte-magazine-1982-09-rescan/page/n277https://archive.org/details/byte-magazine-1982-09-rescan/page/n299
is where it talks about how it takes over the Apple II. It's a pretty fascinating read where it emulates keyboard inputs and paddle inputs.
There's also a page where someone gets one running and talks about the history of one switch gaming:http://www.pixsoriginadventures.co.uk/apple-ii-adaptive-firmware-card/
The a2dp has a few docs and pictures:https://mirrors.apple2.org.za/Apple...0Cards/Other/Adaptive%20Firmware%20Card/
The later ones had an onboard 65816 and 32KB of ram, but the very first ones were mainly EPROM and RAM.