Transcript Digital Theremin - Computer Engineering

EE 552
High Level ASIC Design Using CAD Tools
Digital
Theremin
Farooq Ahmad
Alesya Bajoria
Tim Church
Nicolas Lauzon
Albert Ma
Celia Valel
Introduction



Traditional Theremin
The Theremin is a musical
instrument invented in 1919
by Russian physicist Lev
Termen.
Two antennas protrude from
the Theremin – they use a
variable capacitance to
measure the proximity of the
musician’s hands.
Approaching vertical antenna
increases pitch while
horizontal antenna controls
volume.
Objective
Our goal is the development of a digital
instrument that can be played without direct
contact.

VHDL and the XSA-100 Spartan-II Prototyping
Board with XST-1 Xstend Protyping Extender
Board were used.

IR sensors measured the distance of the
musician’s hands from the instrument.
Features
 Hands
can be moved
from 10 cm to 80 cm
from the sensors for
volume and pitch
control.
 Minimum
frequency of
980 Hz and maximum
frequency of 2.9 kHz.
 Switch
allows the
musician to sustain a
particular pitch.
 Switches
allow selection
from various wave shapes:
Design
Composed of three main components:
1. Input Interface 2. Numerically Controlled Oscillator 3. Output Interface
Sustain
Frequency
Switch
MC33172P
Operational
Amplifier
GP2YOA21YK
Distance
Measuring
Sensor
(pitch)
ADC974
Analog to Digital
Converter (16-bit)
Input
Interface
(serial-parallel
conversion,
ADC control)
Phase
Accumulator
Look Up Table
(for frequency/
wave shape)
selection
GP2YOA21YK
Distance
Measuring
Sensor
(volume)
ADC974
Analog to Digital
Converter (16-bit)
MC33172P
Operational
Amplifier
Input
Interface
XSA-100 Spartan-II
Prototyping Board
Volume
Modulator
Output
Interface
(parallel-serial
conversion,
Codec control)
20-bit stereo
audio codec
(serial-parallel
conversion,
ADC control)
Wave
Shape
Selector
to speaker
Input Interface
MC33172P
Operational
Amplifier
GP2YOA21YK
Distance
Measuring
Sensor
 Sharp
ADC974
Analog to Digital
Converter (16-bit)
 Op-amp
Input
Interface
(serial-parallel
conversion,
ADC control)
GP2Y0A21YK
distance sensors measure proximity of hand by output
of voltage from 2.5 V to 0.4
V as an object moves from
10 cm to 80 cm from it.
reduces loading.
 Analog Devices AD974,
converts analog output
from the distance sensor to
16-bit serial data stream.
 VHDL module controls
ADC and converts its serial
output to a parallel data
vector to be used by the
numerically controlled
oscillator.
 Nonlinear output of distance measuring
sensor was linearized using a VHDL
module.
IR Sensor Output Voltage vs. Distance From Sensor with Amplifier
4.25
4
Output Voltage (V)
3.75
3.5
3.25
3
2.75
2.5
2.25
2
1.75
1.5
1.25
1
0.75
0
10
20
30
Distance (cm)
40
50
Numerically Controlled Oscillator


This component is responsible for outputting a sine,
square, triangle or sawtooth wave of a frequency and
amplitude controlled by the output of the IR sensors.
It consists of a:
o
Phase accumulator
o
Wave look up table
o
Volume modulator
Phase
Accumulator
Wave Look-Up Table
(on-chip RAM)
Volume
Control
to output
interface
+
volume control
word
wave select
word
Phase Accumulator
 The
first stage of the NCO is a phase
accumulator, which produces an output
dependent on a parallel data word (proportional
to the desired pitch) from the IR sensor.
 A counter is increased in increments of this word,
and wraps around every time it overflows. The
numbers in the counter correspond to the phase
of a sine wave increasing from 0 to 2*pi. The
resulting wave shape is a wave with a frequency
of
fout = fclk x FCW/2j
where fclk = the clock frequency, FCW =
frequency control word from the IR sensor and j =
size of frequency control word.
Wave Look-Up Table


The wave look up table will contain a single phase of each of the
sine, sawtooth, triangle and square waves.
These values, which are stored for the use of the NCO, will be
done so on the 40kbits of block RAM.
Sintable
Frequency
Variable Counter
ROM_address
Lut1
Sound_select
Lut2
Lut3
Lut4
Multiplexor
Output waveform
Lut5
Volume Multiplier


The output from the distance measuring sensor responsible for
volume control will be sent to a multiplier.
In this way, the amplitude of the output signal will be modified.
Sintable
Sound_select
Lut_Controller
Multiplier
Frequency
Output
Waveform
Lut1
Lut2
Lut3
Lut4
Lut5
Volume
Wavemaker
Block RAM
Output Interface
From NCO
Output
Interface
(parallel-serial
conversion,
Codec control)
20-bit stereo
audio codec
To speaker
 The 16-bit parallel output from the
volume modulator is converted into serial
data.
 This serial data will be fed to the 20-bit
stereo codec which is present on the XST2 XStend board.
 The audio codec accepts the serial bit
stream from the XS board and converts it
to two analog output signals.
 The signals are fed into an amplifier and
output through a speaker.
Conclusions
This
project has been successful in
introducing a modern twist to an
instrument that is has had an eightyfive year life span.