The digital tuner project involves building a digital tuner board that can sample an analog guitar input signal, convert it to digital, perform digital signal processing to determine the note and tune, and display this information to the user. The team will construct the hardware including a microcontroller, microphone, filters, and LEDs. The microcontroller will implement the digital measurement chain to sample and convert the analog signal, calculate the frequency spectrum using Fourier transforms, and match the frequency to known note values. It will communicate the results to the user via blinking LEDs.

1. Digital Tuner
Project
Team Haribo
Jen, Mihir, Mike, Sami, and Zack

2. Overview
• Project Overview
• Hardware Building
• Digital Measurement Chain Implementation
• Digital Signal Processing
• Digital Tuner Microcontroller Programming

3. Project Overview
The Digital Tuner Project consists of:
• Building a Digital Tuner Board
• Sampling and conditioning input signals
• Converting input analog signals to digital
• Processing and analyzing digital signals
• Determining guitar string note and tune
• Relaying sensor data to the user via LEDs

4. Project Overview

5. Hardware Building
The Digital Tuner Board is constructed from
soldering electronic components, including:
• Atmega1284P microcontroller
o Runs C code ("Brain" of the board)
• USB to UART transmitter
o Thing that connects to the computer and sends/
listens for messages
• Microphone
o Captures input sound signals

6. Hardware Building
Functional components of the Digital Tuner
Board:
• Microphone (input)
• Operational amplifer
• Low-pass filter
• Analog-to-digital converter
• Microcontroller
• LEDs (output)
• USB to UART transmitter (output)

7. Hardware Building
Microcontroller
USB to
UART
transmitter
LED lights Microphone
Buttons

8. Digital Measurement
Chain
The Digital Measurement Chain (DMC)
consists of six stages:
• Signal input
• Signal conditioning
• Anti-aliasing
• Sample & Hold
• Analog to Digital Conversion
• Digital Signal Processing
• Output

9. DMC Implementation

10. DMC Implementation
Digital Tuner Board hardware already achieves:
• Signal Input (Microphone)
• Signal Conditioning (Op amp)
• Anti-aliasing (Low-pass filter removes
erroneous artifacts from input signal)

11. DMC Implementation
Digital Tuner Board microcontroller accomplishes:
• Signal sampling
• Analog-to-digital conversion
o Converts analog signal to digital signal
• Digital signal processing
o Performs transformations and analyzes signal to
determine guitar note and tune
• Output
o Transmits information to computer over bus line or
blinks LEDs to communicate with the user

12. DMC Implementation
Digital Tuner Board microcontroller accomplishes:
• Signal sampling
• Analog-to-digital conversion
o Converts analog signal to digital signal
• Digital signal processing
o Performs transformations and analyzes signal to
determine guitar note and tune
• Output
o Transmits information to computer over bus line or
blinks LEDs to communicate with the user

13. Signal Sampling
Signal sampling: taking measurement of a
signal at a specified rate and number of
sample points

14. Signal Sampling
Goal: reconstruct the original signal as
accurately as possible!

15. Signal Sampling
What happens if we sample too slow?
ALIASING!

16. DMC Implementation
Digital Tuner Board microcontroller accomplishes:
• Signal sampling
• Analog-to-digital conversion
o Converts analog signal to digital signal
• Digital signal processing
o Performs transformations and analyzes signal to
determine guitar note and tune
• Output
o Transmits information to computer over bus line or
blinks LEDs to communicate with the user

17. Analog to Digital
Converter
Goal: convert analog signals to digital signals

18. Analog to Digital
Converter
Why? Simplified and faster signal processing!
Would you rather work with
analog numbers
(1.239454..., 8.323423...)
or digital numbers?
(1, 2, 3, 4, 5, ...)
Drawbacks: Quantization error

19. DMC Implementation
Digital Tuner Board microcontroller accomplishes:
Talked about in
• Signal sampling the
• microcontroller
Analog-to-digital conversion coding section!
o Converts analog signal to digital signal
• Digital signal processing
o Performs transformations and analyzes signal to
determine guitar note and tune
• Output
o Transmits information to computer over bus line or
blinks LEDs to communicate with the user

20. Where are we?

21. Digital Signal Processing
Goal: Determine which guitar note and tune the
input signal corresponds to
How?
1. Convert signal to frequency domain
2. Calculate signal's amplitude spectrum
3. Determine frequency of input signal
4. Match frequency of input signal to known
guitar string frequencies

22. Digital Signal Processing
Goal: Determine which guitar note and tune the
input signal corresponds to
How?
1. Convert signal to frequency domain
2. Calculate signal's amplitude spectrum
3. Determine frequency of input signal
4. Match frequency of input signal to known
guitar string frequencies

23. The Fourier Transform

24. The Fourier Transform
Why? Easier to determine the frequency of the
input signal!

25. Digital Signal Processing
Goal: Determine which guitar note and tune the
input signal corresponds to
How?
1. Convert signal to frequency domain
2. Calculate signal's amplitude spectrum
3. Determine frequency of input signal
4. Match frequency of input signal to known
guitar string frequencies

26. The Amplitude Spectrum

27. Digital Signal Processing
Goal: Determine which guitar note and tune the
input signal corresponds to
How?
1. Convert signal to frequency domain
2. Calculate signal's amplitude spectrum
3. Determine frequency of input signal
4. Match frequency of input signal to known
guitar string frequencies

28. Matching Frequencies
Frequency (Hz) Guitar Note
82.41 Low E
110.0 A
146.8 D
196.0 G
246.9 B
329.6 High E

29. Matching Frequencies
In tune? Frequencies falling
Frequency (Hz) Guitar Note
in between these regions
82.41 Low E
are considered flat or sharp
110.0 A
notes
146.8 D
Digital Tuner Accuracy?
Due to low precision in 196.0 G
the ADC and hardware 246.9 B
limitations, frequency 329.6 High E
calculations are

30. Microcontroller
Programming
The aforementioned digital signal processing
steps all take place in the microcontroller!
C programming!

31. User Interaction
The Digital Tuner Board communicates the guitar
note and accuracy to the user, via LED lights.

32. Questions?