Adafruit charlieplexed led matrices 16x9 adafruit 2948 the adafruit charlieplexed yellow led 9x16 matrices give you boards full of bling with 144 x 0603 surface mount leds with traditional multiplexing you would need 25 gpio lines 9 16 to drive these boards which would soak up most of the signals on common microcontrollers however these boards are charlieplexed which is a clever way of doing more with less using only 18 gpios they can best be described as lean at only 24mm thick a