You've seen LED cubes, they are everywhere, but this one is unique in it's size. The edge of this 4x4x4 is just about 1cm long, the total size including the epoxy casting and the driver circuitry is 13x13x37mm
The LEDs are driven in a charlieplexed arrangement, which allows to group them in "stacks". The custom, assembler optimized code can create true 24bit RGB colors at a flicker-less frame rate of 120hz. In addition to the ATMEGA328PB microcontroller the build includes a step-up converter, a LiPo charger IC, an accelerometer and a 1Mbit EEPROM.
Right now the firmware is missing a few features I had planned. Do to time constraints I decided to publich the completed hardware as well as the fairly robust demo code. The whole project (including more hi-res images) is documented on inctructables.com, link down below.