3-pin Charlieplexing configuration with common resistors to drive six identical LEDs with the minimal number of port signals. This variant illustrates the rows and columns in an expandable Charlieplexing matrix, however, it still does not allow to reliably power more than one LED at the same time, as multiple LEDs must not shorted in order to drive them through a common resistor. LEDs have manufacturing tolerances and shortening multiple LEDs without individual balancing resistors would significantly reduce their lifetime.
Own work
Matthiaspaul