[Coco] Recreating the CoCo keyboard

Ciaran Anscomb cocomalt at 6809.org.uk
Wed Oct 21 12:38:39 EDT 2020

Rick Ulland wrote:
> I expect CoCo game designers just learned 
> which keys clashed during testing and didn't use those.

Yeah - can be quite difficult to support even just two players
simultaneously...  More so if you then have more on joysticks (because
the firebuttons take out two whole rows of possible keys).

(and said this in a slightly different order):
> Elsewhere, some makers would wire 
> the cursor keys WASD so a double press here was on separate cols and 
> rows and less likely to ghost.
> [...]
> I kind of assume this is all obsolete stuff. Don't modern keyboard 
> controller chips use an N-key (strobed or whatever) matrix so it's up to 
> your interface?

You'd think!  Diodes cost money, so most keyboards still just do what you
described and group stuff such that normal use doesn't cause a problem.

> PS : LTT once demoed an N key rollover usb keyboard that got around the 
> 6 key limit by installing itself as multiple keyboards in device manager.

Neat!  Of course, now I want this from any subsequent keyboard (wishes,
fishes, ...).


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