This is something that I made earlier but rediscovered buried in the mess on my workbench. It is a small three board gadget with four 8-pin ATtiny45 microcontrollers, each driving 6 charlieplexed LED’s.
The ATtinys share a common ISP connector, and use a DIP switch to select the controller whose reset would be triggered by the programmer. The common ISP signals can be used to let the controllers communicate via a shared bus.
Blinkenlights, wooo. If it keeps raining, I might try to make it display Conway’s Game of Life. :)