Re: Apple 2e - building a simple expansion card and calling it from BASIC (or assembly)?

[David Wilson <mcs6502@gmail.com>]

On Oct 23, 7:11 am, mad.scientist...@gmail.com wrote:
> Has anyone built their own Apple 2 expansion card and programmed it to
> do something?

Yes. Over the years I built a few (using prototyping cards and wire-
wrap wire (soldered rather than wrapped)) including a ROMDisk
(bootable), a dual port serial card (2x 6850 ACIAs) and a clock card.

> If it wouldn't be ridiculously hard, I would like to try etching a
> circuit board to plug into one of the expansion slots on my 2e. The
> board would contain a single relay, which could be opened or closed
> from BASIC code (or if it is not possible from BASIC, from 6502
> assembly).

If that is all you need, a card attached to the game port would be a
lot simpler to build.

> I'd also like to have the board contain 2 leads that the computer
> could tell when they are connected together.

Again, the game port already has that functionality.

> Maybe later I would expand the # of relays or leads, or build an
> additional card or two, for more "inputs" and "outputs".

If you need more than a few inputs and outputs then you will need a
card in a slot.