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schematic(1.0)
printed
circuit board
(v0.9)
ecasound
boot command
avr
microcontroller code
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Technical
setup:
- Audio
chain
A SHURE SM58 microphone ran to a pre-amp and
then into the on-board soundcard of a VIA
EPIA-V 800mHz K6 motherboard with 512MB of RAM and a 2.1gb hard
drive. Future devices will use a FLASH RAM card for the OS. The
soundcard's output was fed to a splitter, to a headphone amp
and to the voyeur station's amp/speaker. A small tape recorder
inside the voyeur amp recorded segments of the evening for documenation
purposes.
- Control
unit
The dome contained a circuit board with an AVR
microcontroller (AT90LS4433). The microcontroller used its on-board
ADC to convert the three control potentiometer's variable voltage
output, and the four switches binary output into MIDI controller
commands. The knobs outputted continuous controller data on channel
1 (controllers 1, 2, and 3). The switches sent 0x00 or 0x7F on channel
2 (controllers 1,2,3 and 4). The software responded appropriately to
these MIDI commands.
The
code was compiled with the avr-gcc
compiler, and burnt onto the chip using Atmel's AVR STK501
board.
- Software
Ecasound
processed the audio feed using LADSPA
effects. The driver was from the ALSA
package. The system ran Debian
Linux using a low-latency
patched kernel (2.4.25). Boot time was a slow 25s, and could
be improved easily by altering the /etc/rcS.d/ symlinks.
Effects used:
- bodeShifter-
frequency shift was swept up and down at a variable rate by knob
1. North switch is on/off.
- sifter-
cutouff frequency swept up and down at 1/4 rate of bodeShifter.
South switch is on/off.
-
pitch
shift - (ecasound -ei:) frequency manually shiftable by knob
2. West is on/off.
- delay-
75% feedback delay. Time is controlled from 0.2s - 5s with knob
3. East is on/off.
The control
dome sent MIDI signals into the CPU's serial port. The notemidi
driver fed this into ecasound's engine.
- Video
A
black and white security camera (X10) pointed at the confessor's
face, and the image was shown on the television in the voyeur's
station.
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