Download Auto-Chromatic Instrument Tuner

Auto-Chromatic Instrument
Tuner
Erin Smith
Advisor: Dr. James Irwin
Date: November 20th, 2000
Presentation Overview
Project Summary
 Milestones & Critical Problems
 Future Work

Project Summary
Brief Overview of Operation
 State of Received Tuner
 Proposed Modifications

Overview of Operation

The auto-chromatic tuner is a self
contained tool that is used to determine
the pitch and intonation of a musical
instrument in real time
Functional Description

Inputs
– Microphone
– Pitch selector
– Power/Mode Switch

Outputs
– Pitch indicator
– Digital tuning indicator
– Speaker

8031 Microcontroller
Auto-Chromatic Tuner
LED Display
Pitch
Up
E b 6
Pitch
Down
R
Octave
Up
Y
Auto
Tuning
Off
Pitches:
G: Green LED ± 5 cents
Y: Yellow LED ± 5-15 cents
R: Red
LED ± 15-50 cents
G
Octave
Down
Y
Manual
Tuning
Audible
Pitch
R
Audio
In
Microphone
Threshold
Detector
Amplifier
Timer/
Counter
Automatic Gain Control
Clock
- Parts which do
not work, or have
not been included
yet
Divide By 2 Tree
Power/
Mode
Switch
Switched
DC Power
to all subsystems
Overflow
Mode
Bus
Microprocessor
Bus
Display
Control
Analog Meter
DC Power
Tuning LED’s
Pitch
Selector
Frequency
Look-Up
Table
Function
Generator
Speaker
Driver
Pitch
Indicator
Speaker
Selected
Pitch Out
Audio
In
Microphone
Threshold
Detector
Amplifier
Timer/
Counter
Automatic Gain Control
Clock
Divide By 2 Tree
- Parts which were
modified
Power/
Mode
Switch
Switched
DC Power
to all subsystems
Overflow
Mode
Bus
Microprocessor
Bus
Display
Control
Analog Meter
DC Power
Tuning LED’s
Pitch
Selector
Frequency
Look-Up
Table
Function
Generator
Speaker
Driver
Pitch
Indicator
Speaker
Selected
Pitch Out
Start
Initialization
Mode
Audible Reference
Pitch
Read Mode/
Power Switch
Auto Tune
Manual Tune
Setup and
Start Counter
Display Pitch
No
Read Counter
Tuning
Mode
Display Results
Counter
Overflow
Adjust Frequency
Driver
Yes
State of Received Tuner
Auto-tune worked with pre-selected
octave only
 Manual tune supposedly worked, or had
some portion working
 Analog and Digital Tuning worked
 Display worked correctly
 Pieces of software worked, but not all in
one program

State of Received Tuner
Tuner did not work as expected when
connected to power supply
 Programmer was faulty, PAL’s were
broken
 Unit did not work until mid-March
 Analog meter ceased to work (not sure
if problem with hardware or software)
 No software located for manual tune

Proposed Modifications
Manual Tune completion
 Automatic Gain Control
 Expand Digital Tuning
 Auto-Tune Mode completion

Manual Tune
Software for Manual Tune could not be
located
 Scope was too large, given that no code
was available to work from
 Due to time constraints, was not able to
complete Manual Tune mode

Automatic Gain Control

Attempted several different
configurations in the Spring
– Gain circuit with Varistor
– Circuit with an FET
Varistor
Vin
Vout
LPF
Gain circuit with Varitstor in parallel
Low amplitude signal
Vin
Vout
gnd
Gain circuit with FET in feedback loop
Automatic Gain Control
Found article with an AGC circuit which
involves a digital potentiometer
 Parts did not come in, so AGC could not
be implemented

x(t)
y(t)
CONTROL
E(t)
+ _
Eref
AGC Circuit which utilizes a Digital Potentiometer
Digital Tuning
Wanted to expand digital tuning from 5
LED’s to 9 LED’s
 Intended to take place of analog meter
 Expanded the truth/logic tables
 Not enough memory or bits available to
implement the expansion
 Required major re-design of hardware
and doing the wire wrapping over again

Excerpts of Expansion of the Truth Tables
(formerly only A15-A11 needed)
test_vectors
([A15, A14, A13, A12, A11, A10, A9, A8, A7, WR] -> [dac,pitch])
[ 0,
0,
0,
0,
0,
0, 0, 0, 0, 0] -> [ 0,
0];
[ 0,
0,
0,
0,
0,
0, 0, 0, 1, 0] -> [ 0,
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 0, 0] -> [ 0,
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 1, 0] -> [ 0,
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 0, 0] -> [ 0,
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 1, 0] -> [ 0,
0];
([A15, A14, A13, A12, A11, A10, A9, A8, A7, WR] -> [dbt_en])
[ 0,
0,
0,
0,
0,
0, 0, 0, 0, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 0, 0, 1] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 0, 1, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 0, 1, 1] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 0, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 0, 1] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 1, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 0, 1, 1, 1] -> [
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 0, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 0, 1] -> [
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 1, 0] -> [
0];
[ 0,
0,
0,
0,
0,
0, 1, 0, 1, 1] -> [
0];
Auto-Chromatic Tuner
LED/LCD Display
E b 6
Pitch:
R
O
Y
B
Auto
Tuning
Off
Pitches:
G: Green LED ± 3 cents
B: Blue LED ± 4-10 cents
Y: Yellow LED ± 11-20 cents
O: Orange LED ± 21-30 cents
R: Red
LED ± 31-50 cents
G
Octave:
B
Manual
Tuning
Audible
Pitch
Y
O
R
Auto-Tune Mode
Worked with pre-selected octave only
 Learned how Timer 0 Overflow worked
in relationship to counting the period
 When overflow occurred, decremented
the octave and reset the divide by 2^n
 Once a pitch is successfully detected,
reset the divide by 2^n to the 9th
octave
 Device is then ready to search again

Milestones & Critical
Problems

Critical Problems
– Unit did not work initially
– Not enough memory to expand LED’s
– Lack of software for manual tune
– Parts for AGC did not come in
Milestones & Critical
Problems

Milestones
– Getting unit up and running
– Expanding tables for LED’s
– Determined a good duty cycle and
waveform for the Audible Reference Pitch
with a function generator
– Determined design for AGC circuit
– Successfully implementing Auto Tune Mode
Future Work
Manual Tune
 Audible Reference Pitch
 Expanded LED Display
 Packaging
 Automatic Gain Control
 New Hardware:microphone, speaker,
CPU, and memory

Any Questions?