GuitarE Tuner

A real-time guitar tuner using FFT on the Raspberry Pi Pico W

info

Author: Yelyzaveta Basiuk
GitHub Project Link: https://github.com/UPB-PMRust-Students/project-yomotoua

Description

This project is a digital guitar tuner that captures audio signals through a microphone, processes the signal using Fast Fourier Transform (FFT), and displays the nearest musical note in real time. It runs on a Raspberry Pi Pico W using Rust.

Motivation

I recently started learning how to play guitar, and I thought it would be fun and useful to build a tuner myself. I'm also just getting into embedded systems and Rust programming, so this project is a way to explore both while building something real. It’s a learning experience where I get to combine simple electronics, sound processing, and coding.

Architecture

The diagram above shows the overall system architecture of the guitar tuner.

Architecture Details

Raspberry Pi Pico W

Role: Reads the analog signal from the microphone, processes the signal using FFT to extract the frequency, handles note selection from button input, controls the display, and manages LED output.
Connections:

• ADC pin for microphone input
• GPIO pins for button inputs
• GPIO pins for LEDs
• I2C for the LCD display
• Powered via USB or regulated 5V from a battery

Microphone Module (Analog)

Interface: ADC
Role: Captures the sound produced by the guitar strings and converts it to an analog signal.
Connections:

• Signal output connected to ADC pin
• Powered with 3.3V and GND

Push Buttons (x2)

Interface: GPIO
Role: Used to scroll left/right through available tuning notes (E, A, D, G, B, e).
Connections:

• Each button connected to a GPIO pin
• Configured with pull-up/pull-down resistors and interrupts

LEDs (x6)

Interface: GPIO
Role: Indicates which note is currently selected by lighting up the corresponding LED.
Connections:

• Connected to GPIO pins
• Each with a 220Ω current-limiting resistor

LCD Display (I2C)

Interface: I2C
Role: Displays the detected frequency, and a tuning status indicator (flat / in tune / sharp).
Connections:

• SDA, SCL
• Powered from vbus and GND

Power Supply

Interface: USB or battery + regulator
Role: Provides power to the whole system.
Connections:

• USB via micro-USB (for development)
• Optional 9V battery connected via voltage regulator (outputting 5V)

Log

Week 5 - 11 May

This week I finalized the basic design for the project and gathered all the necessary components. I focused on checking that everything works correctly and started outlining the system architecture. I also worked on the initial documentation. I began testing the microphone to see if I can get a stable signal through the ADC. If that works, I’ll move on to the next steps in signal processing and note detection.

Week 12 - 18 May

Week 19 - 25 May

Hardware

The system is built around a Raspberry Pi Pico W. It uses an analog microphone to capture the guitar sound, two push buttons to select the target note, and LEDs to indicate which note is currently selected. A small LCD display shows the detected frequency and tuning status. The project is powered by a 9V battery with proper voltage regulation for portability.

Fig.1 – Prototype setup on breadboard

Fig.2 -

Schematics

Fig.3 – Initial Schematic

Bill of Materials

Device	Usage	Price
Raspberry Pi Pico W	The microcontroller	35 RON
Amplificator Microfon MAX9814	Captures guitar sound	~10 RON
I2C LCD Display	Displays selected note and detected frequency	~25 RON
Push Buttons x2	Used to select target note	~0.35 RON
LEDs x6	Indicate selected note	~3 RON
Resistors & Breadboard Wires	For basic circuit setup	~15 RON
9V Battery + Holder	Power source	~8 RON

Software

Library	Description	Usage
embassy	Async embedded framework for Rust	Used for async task management, timers, and peripherals
microfft	Lightweight FFT implementation	Used to extract frequency from microphone input
hd44780-driver	LCD driver for HD44780-compatible screens	Used to display detected frequency and note
defmt	Embedded logging crate	Used for debugging and printing ADC/frequency values
libm	Math library for no_std environments	Used for floating-point math in signal processing
num-complex	Complex number support	Used to work with FFT results from microfft

Links

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