Game Port Interface Board

The interface board was built by Andrew in November 2011. He made it so Ivan could connect his Apple //e to Snap Circuits, but, it can be used to connect to anything that uses low voltage, like K'NEX motors, sprinkler valves, Estes rocket engine igniters, etc. Below are the pin-outs for the Apple //e game port; and, how PB0 .. PB2 (push-button inputs 0, 1, 2) & AN0 .. AN3 (annunciator outputs 0, 1, 2, 3) map through the external interface keeping the Apple //e electrically isolated by using micro-relays and optocoupler ICs.

  Pinouts for Apple //e Game Port
16-pin DIP (Dual Inline Pin) socket
+5V     | 1   16 | Not used
PB0     | 2   15 | AN0
PB1     | 3   14 | AN1
PB2     | 4   13 | AN2
Strobe  | 5   12 | AN3
GC0     | 6   11 | GC3
GC2     | 7   10 | GC1
Gnd     | 8    9 | Not used
 Pinouts for Interface Connector
20-pin DIP (Dual Inline Pin) plug
    Black -+ nc   nc +- White
off Grey  -+  +SW3-  +- Purple 0v
off Blue  -+  +SW2-  +- Green  0v
off Yellow-+  +SW1-  +- Orange 0v
 o\ Red   -+ncc | ncc+- Brown  /o
  o Black -+ AN3|AN2 +- White  o
 o  Grey  -+noc | noc+- Purple  o
 o\ Blue  -+ncc | ncc+- Green  /o
  o Yellow-+ AN1|AN0 +- Orange o
 o  Red   -+noc | noc+- Brown   o

Don't want to wait for K-Fest 2015 to start connecting your Snap Circuits to your apple //?
Well, that's understandable, although, we promise to make our board available / for sale by then.
In the mean time, here's the very basic design of how we did it - you can do it, too.

Yes, you can do it differently. You can for example drive circuits directly from the output of the optocoupler. But we use a relay because that gives us both Normally Closed and Normally Open contacts which can easily replace any switch in any Snap Circuit (eliminates the need for Dad to have to check the kid's 'wiring' all the time). You can also use other components to create an interface for yourself, which you'll find other folks have done if you search the 'net. But, this is how we did it, and we've had really good luck with it.