Guitar Tuner

Used to tune your guitar

info

Author: Magureanu Alin
GitHub Project Link : https://github.com/UPB-PMRust-Students/project-Alin1502

Description

The project consists of a guitar tuner that helps the user to accurately tune each guitar string without the need for external devices or application. Firstly, the sound is captured by the MAX9814 microphone and is sent to the microcontroller. The Raspberry Pi Pico analyzes the signal using Fast Fourier Transform in order to determine the dominant frequency. The obtained frequency is compared to the standard tuning values and identifies the closest musical note. After all the computations, the obtained note is shown on the OLED Display and the buzzer replicates the sound of the chord. For simplicity of the user interface, the user can select which string he is currently tuning using a push button.

Motivation

As someone who started to play guitar recently, I found it frustrating that my guitar was getting out of tune frequently. While there are mobile apps available for tuning, I disliked the idea of always depending on a phone and internet access to perform this. By researching how to detect sound frequencies, process them and display them in real time, I was able to create my own, fully functional device for tuning the guitar.

Architecture

1. Raspberry Pi Pico: used for handling the logic of the project. It receives analog audio input from the microphone, makes it digital using ADC and performs signal processing to detect the frequency
2. Microphone Module: captures the sound of the guitar being plucked, which is then sent to the microcontroller
3. OLED Display: displays when the chord is in tune and the current string selected
4. Push Button: prompts the user to select between the 6 chords ( E, A, D, G, B, E) to select what to tune.
5. LED: blinks red when guitar is out of tune, green when it is in tune
6. Buzzer: replicates the sound of the respective chord after it gets in tune

Log

Week 28 April - 4 May

I started working on the documentation for the project. I bought every necessary component and i started to connect them on the breadboard, in order to be able to make the schematics and understand how they interact with eachother.

Week 5-11 May

This week I started looking into how to use the Fast Fourier Transform (FFT) to detect the frequencies from the microphone. I needed this to figure out which string is being played on the guitar.I learned how to take audio samples, remove the DC offset, and apply the FFT using the microfft crate.

Week 12-18 May

I implemented the other components : the push button to select between strings, and the two led's to display the tuning status. I still have issues with computing the correct frequency of each string, as there is a lot of background noise detected. The display is working aswell, displaying if we should tune upwards, downwards or if it's in tune.

Week 19-25 May

I succesfully completed the software part of the project. The tuner is now capable to detect accurately the frequency of each guitar string. I also improved the user interface part, providing clear feedback on the display.

Hardware

1. Raspberry Pi Pico 2
   Main control unit. Coordinates all used components - the microphone, the buzzer, the led's and the display. It performs signal processing to analyze the audio input and determine the string's frequency.
2. MAX9814 Microphone
   Captures audio. Detects the sound and sends the analog signal to the pico's analog-digital converter.
3. Push Button
   User interaction. Allows the user to cycle through guitar strings for tuning and is used to move to the next chord after a string gets tuned.
4. LED's
   Visual tuning indicators. When the correct frequency is detected, it means the guitar is in tune and the green led turns on. Otherwise, the red led is constantly turned on during the process.
5. Active Buzzer
   Audio feedback. Sounds a confirmation tone when a string is tuned correctly, providing audible confirmation alongside the green LED. The tone of the buzzer coresponds the sounds of the respective string.
6. OLED Display
   Display status. Shows messages such as the current string tuned or whether we need to tune up or down.
7. Step Down Power Supply
   Using a battery and the LM2596s, we will power the whole circuit such that it is portable and we can use it anytime

Schematics

Bill of Materials

Device	Usage	Price
Raspberry Pi Pico 2W	The microcontroller	40 RON
Raspberry Pi Pico WH	The Debugger	39 RON
MAX9814	Microphone Module	60 RON
9V Battery	Power the circuit	20 RON
LM2596s Step Down	Power the circuit	13 RON
Push Button	Select Button	0.36 RON
OLED Display	The Display	30 RON
LED	Blink LED	0.4 RON
Buzzer	Replicates Sound	1.4 RON

Software

Library	Description	Usage
defmt, defmtrtt	Efficient Logging	Used for detailed logging and debugging
ssd1306	Display Library	Used for I2C OLED Display
embassy-rp	Pico Peripherals	Used for accessing the peripherals
num-complex	Complex Numbers Library	Used to compute complex part of fourier
microfft	Fourier Transform Library	Used to compute frequency with fourier
embassy-time	Time management library	Used for time-based operations such as delays
embassy-executor	Async/Await executor	Used for asynchronous programming and timers
embedded-graphics	Text library	Used for text and shapes
heapless	Memory allocation	Used for String
libm	Math Library	Used for math functions

Links

1. Clap Switch
2. Fundamentals and Harmonics
3. Video Demo for Tuner