ESP32 Guitar Tuner

A real-time guitar tuner and chord detector built with ESP32 and an INMP441 I2S microphone. Features a web-based interface with Gruvbox dark theme for visual feedback.

Features

• Real-time Processing
• Guitar Tuning Mode
• Chord Detection Mode
• Web Interface

Hardware Requirements

Component	Description
ESP32	ESP32-S3 is used but any ESP32 board with I2S support should work
INMP441	I2S MEMS microphone
Jumper wires	For connecting microphone to ESP32

Wiring Diagram

INMP441    ESP32
------     -----
VDD        3.3V
GND        GND
WS         GPIO25
SCK        GPIO26
SD         GPIO33
L/R        GND

How It Works

Signal Processing Pipeline

1. Audio Capture: I2S microphone captures audio
2. FFT: FFT realised using ESP-DSP library

Tuning Algorithm

1. Harmonic Product Spectrum (HPS): Compresses spectrum at multiple harmonic ratios to find fundamental frequency
2. Quadratic Interpolation: Refines frequency estimate between FFT bins
3. Octave Correction: Validates detected frequency against harmonic relationships
4. Note Matching: Finds closest note in chromatic scale and calculates cents offset

Chord Detection Algorithm

1. Pitch Class Extraction: Maps frequency components to pitch classes (C, C#, D, etc.)
2. Energy Accumulation: Aggregates pitch energy over multiple frames
3. Template Matching: Compares against major/minor chord templates using dot product
4. Classification: Returns chord with highest match score above threshold

Installation

Prerequisites

• ESP-IDF v5.0 or later

Build and Flash

# Navigate to project directory
cd src

# Build the project
idf.py build

# Flash to ESP32 (replace PORT with your serial port)
# Linux: ls /dev/ttyUSB0 or /dev/ttyACM0
# macOS: ls /dev/cu.usbserial-*
idf.py -p PORT flash

# Monitor serial output
idf.py -p PORT monitor

You could also use the ESP-IDF extension in Visual Studio Code.

Usage

Tuning Mode (Default)

1. Flash the firmware to the ESP32
2. Connect to WiFi network ESP_GUITAR_TUNER (password: 12345678)
3. Open browser and navigate to IP adress provided, usually 192.168.4.1
4. Go to the Tuner page and play a string
5. The display shows detected note, frequency, and cents deviation

Chord Detection Mode

1. Open main/main.c and change the mode flag:

   #define CHORD_DETECTION_MODE  1

2. Rebuild and flash the firmware
3. Connect to the WiFi and web interface as above
4. Strum a chord and view detection in serial monitor

Web

References

• FFT-based Pitch Detection
• ESP-DSP Library
• ESP-IDF Programming Guide