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From: midkiff@portia.Stanford.EDU (Neil Midkiff)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Mac II ADB autostartup
Message-ID: <1990Aug29.103618.6714@portia.Stanford.EDU>
Date: 29 Aug 90 10:36:18 GMT
References: <2109@idunno.Princeton.EDU>
Organization: AIR, Stanford University
Lines: 44

In article <2109@idunno.Princeton.EDU> rlwald@phoenix.Princeton.EDU 
(Robert L. Wald) writes:
>
>  How does the Mac start up from the keyboard and how difficult would
>it be to put something on the ADB bus which would simulate this? I 
>want to set up a timer to autostart my mac. 

From page 291 of _Guide to the Macintosh Family Hardware_ (2nd ed.):

Pin 1 of ADB connector is the bidirectional data bus (open collector,
pulled up to +5V through 470 ohms)
Pin 2 is the power.on line.  A key on the ADB keyboard momentarily
grounds this pin to pin 4 to switch on the power supply on the Mac II
family.  On other models, this pin is not connected.
Pin 3 is +5 volts
Pin 4 is ground.

Here's where it gets tricky.  The picture of the connector doesn't say
whether it's the male or female connector; I would guess that it's the
female chassis connector, but CHECK IT OUT before trying to short pins
together! 

                       ^^XX^^
                     ( 4    3 )
                    (          )
                    ( 2      1 )
                     (X [[]] X)
                       \____/

Wow, that isn't very round, is it?  The 1 2 3 4 are pins (or sockets
for pins), the X's are notches for orientation, the [[]] is the
rectangular alignment plug, and all the other marks are my very
inartistic attempt at an ASCII circle.

Probably the safest test is to unplug the keyboard from the Mac (power
off first, of course) and use an ohmmeter on the pins of the plug that
goes into the Mac, to see which pins get connected when the power-on
switch is depressed on the keyboard.

Then all you need is a relay driven by an alarm-clock chip (most of them
have logic outputs, I think) to make your auto-starting Mac a reality.

Good luck!
-Neil