The Cubatron - LED PingPong 3D Display
The Cubatron is the world’s largest true 3D color graphics display (until the BRC is built in August 2006). It is 8×8x8 feet in size. It consists of 729 voxels (3D pixels) arranged in a 9×9x9 matrix, spaced 10 inches apart from each other. Each voxel is a 40mm diameter ball that can be independently set to display a 21-bit RGB color. The entire display can be updated about 30 times per second. The voxels “float” in space so that the viewer can see through the cube and have a view of most of the voxels from any position.
There are 729 voxels. Each one has a microcontroller on it. There are 27 strings of 27 voxels. The voxels on each string have an address of 1 through 27. They are sent commands using a special synchronous protocol which consists of a frame which contains RGB data for each of the 27 voxels on the string. A frame is sent on every string about 30 times per second. The voxels take the last RGB value they got and PWM the RGB LED to display the proper color.
A PC running FreeBSD generates the patterns to display. The PC converts the RGB data into the 27 streams of data to be sent to each string of voxels. It sends this data across an ethernet connection to an ethernet printer server. The printer server’s parallel port outputs data to the voxel driver board. The voxel driver board has a PIC18F452 which demuxes the incoming data and sends it out to the 27 voxel strings while maintaining proper timing for the synchronous protocol. The Cubatron requires 100K bytes of data per second.
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