So I just happen to have one of the keypads you just added to the store lying around (what are the odds of that?) and was psyched to give the tutorial code a try. Everything behaved as expected with one exception. P9 on socket 9 did not work. When any of the third column of keys was pressed, ReadMatrix() returned false. I went through a bunch of troubleshooting to make sure my keypad was good, extender well soldered, etc… only when I switched to socket 6 did all keys work as expected.
The only other thing plugged into the Spider is the display, which is not used. The code is verbatim from the tutorial, other than the socket number change.
Can somebody smarter than me explain why this might be?