PROJECTS:: PIIXELMUSIIC 3000
BEHIND THE MUSIC VISUALIZER
The $12 Propeller microcontroller lacks sufficient RAM for a frame
buffer, so it can’t produce any-and-all video imagery. But it’s powerful
enough to synthesize a real-time NTSC television signal that renders
geometric shapes and colors.
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HARDWARE 3 The potentiometer lets 5 The resistor ladder 7 Pin 16 of the microproces-you manually adjust the divides and recombines sor (not shown) connects to a
1 Stereo signal from the reference voltage that the 3 digital outputs from the red indicator LED (not shown
audio cable is split on the ADC compares left and right microprocessor to produce on breadboard). The software
circuit board. Half is carried channel volume levels to. You an analog NTSC video signal, switches the LED on to show
back out by the A/V cable, may find small increments at the pre-HD standard for TVs that it’s running successfully.
and the other half feeds the the edge have a big effect. in North America, Japan, and
analog-to-digital converter elsewhere. 8 The EEPROM chip (ADC). (electrically erasable
memory) stores the software
on the board between power-ups. The chip is intentionally
installed upside down on
the board so you can easily
ground 4 of its pins at once.
4 The Propeller microprocessor runs software (see
2 The ADC chip converts below) to create visuals
analog value levels into based on input from the
digital values that are usable ADC (pins P0–P2). It out-
by the microprocessor. puts them (pins P12–P14)
as a digital precursor to
6 The A/V cable takes
the original stereo signal
and the generated NTSC
video out to a TV or home
The Pixelmusic software “paints” simple shape layers using a limited palette
of 70s-compatible colors. Their size, orientation, and color palette are controlled by volume changes in the left and right channels of the music. One
of 8 different shape layouts is randomly selected each time there’s a sudden
change in volume. Like the original AVM, the Pixelmusic doesn’t look at frequencies, beats, or anything fancy; just the left and right channel volumes.
But because our brains are wired to make audio-visual correlations, this is
enough to make people swear that the patterns are dancing to the music.
Illustration by Damien Scogin
116 Make:: Vollume 114