The Walcott visualization integrates a set of rewired christmas lights into the Bemix system. A custom XMMS plugin running on Cocoa Table calculates five 0-255 values based on Fourier transform of the music playing in the lounge. These numbers are wrapped into a 4E Network packet and sent to the serial port to a PIC microcontroller. The PIC parses the packet using BemixOS technology and sets the brightness of each color of light using PWM.
The visualization uses a PIC 18F1220 to decode a 4E Network packet containing six 0-255 values. The packet should look something like:
\ H v (ignored) (ignored) (channel 1) (channel 2) (channel 3) (channel 4) (channel 5) (channel 6) \ E
These values become the duty cycles of six software PWMs running in the main loop of the firmware. The latest version of the firmware is available at svn://bemix.mit.edu/var/svn/repos/visualization/pic.
The PWM outputs are fed into TIP110 power darlingtons through 1K base resistor. The power transistors are connected to a set of modified christmas lights in a common emitter configuration. Each TIP110 drives an array of two lights in series and n in parallel. The lights are powered from the +5V rail of a computer power supply.