Inspired by Charlieplexing, I made a circuit that allows 4 pins to control 12 LEDs.
Not so impressive, but in this way 5 pin control 20 LED, 6 pin control 30 and so on. #Led = n ^ 2-n; n = #pins.
see:https://en.wikipedia.org/wiki/Charlieplexing
Now it is connected in 4 blocks of 3 pins. It is thought that only one pin is High and one is Low. The others should be disconnected, Think input on an MCU.
