HACL is a DIY project, where 12, 24 (etc) LEDs are mounted into a surface of an analog clock, and are used to signal incoming MIDI Signals
The firmware defaults to listening on all MIDI channels, but there is a simple interface option provided, consiting with a potentiometer and three buttons, which enables preview only some channels. An alternative mode which unfolds two octaves (To differntiate between alternate octaves)
Created in 2010, First presented on London Music Hackspace meeting in 2011
http://musichackspace.org/arduino-based-harmonic-clock-project/
Hardware consits of a standard Arduino MIDI input, and a set of basic serial shift registers to drive the LEDs (Simplified schematic below, and in the video)
Introduction video (Youtube):
https://www.youtube.com/watch?v=eOKvnIQ3gmY
Usage Demos:
https://www.youtube.com/watch?v=_Yh4oojIDO4
https://www.youtube.com/watch?v=DKcpQGguL5g
There is no schematic as such, as the board was just soldered on a stripboard without much thought, but its simple enough to figure out. Leds are driven via three shift registers connected in serial. Features of the firmware are: parsing midi notes, controlling note flashing and fades, interface control. There is simple midi processing routnie drafted but it doesn't do anything terribly useful at the moment.
Pull requests welcome