Term of art: " Charlieplexing " Oh, and hey, come to think of it, this has got to be what's going on in the makeymakey firmware, the bits that look like so: pinMode(inputLED_a, INPUT); digitalWrite(inputLED_a, LOW); pinMode(inputLED_b, OUTPUT); digitalWrite(inputLED_b, LOW); pinMode(inputLED_c, OUTPUT); digitalWrite(inputLED_c, HIGH); I was wondering what the hell was up with that. --- Aha, yes, I can see the charlieplexing going on here: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Arduino/Boards/makey_makey-v12.pdf