Charlieplexing

Do you think it is possible to drive an 8-digit, 7-segment display with only nine (9) connections? Yes certainly, and here we show you how it’s done.
Normally speaking, a 7-segment display has eight LEDs (including the decimal point) that have to be controlled with eight inputs and one common output. The corresponding segments of all the displays are connected together and only one display is activated at a time because each display has its own common anode (or cathode) connection.