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Re: Keyboards

In article <1028527966-960630223311@rook.wa.com>,
Steve Townsend <steve.townsend@rook.wa.com> wrote:
>     
> Jack,
>     You wrote:
> Quote|
> Quote|   For that matter, not all mac keyboards work.  The
> Quote|early ones (prior to the SE or SE 30) where the keyboard
> Quote|had the phono plug to connect to the computer do not
> Quote|work...wrong plug to go into the IIGS.  There also seem to
> Quote|be problems with some of the last keyboards....especially
> Quote|the ergonomic (multiple part/moveable) ones as per other
> Quote|online discussion
>     
>     True, but both of these keybards have for wires in their
> cables.

[I assume you mean "four" wires.]

> Is it possible to rewire one of the older Mac keyboards
> to work on the newer Macs or the GS?

No.  Newer Macs and the IIgs use the Apple Desktop Bus to interface to
the keyboard.  This involves a reasonably complicated bidirectional
protocol, making use of one of the four wires in the ADB cable.  Two
of the remaining wires are power and ground, and the last wire is only
used on a Macintosh to turn the machine on (using the Reset/Power key).

I don't know exactly how the original Mac through Mac Plus keyboards
worked, but they certainly were using the ADB protocol.  It is
probably a simple scheme like the PC, with a clocked serial data
stream being generated by the keyboard.  One wire will be clock, one
will be data, and the other two will be power and ground.  The
keyboard simply sends a byte of data to the computer whenever a key
is pressed or released, indicating the "scan code" of the key.  The
Mac transforms this into an appropriate ASCII code.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand