MIDI Keyboard

Project Overview

This project is a fully custom-designed MIDI keyboard, developed end-to-end by designing, fabricating, assembling, and testing a multi-layer PCB. The keyboard uses a microcontroller-based key scanning system and communicates MIDI signals over USB, allowing seamless integration with digital audio workstations (DAWs) and music production software.

Key Functions

• Sensing: Detects which keys are pressed using 4 x 6 key matrix connected to ESP32

• Compute: The ESP32-S2-SOLO-N4 processed key inputs and encodes them as MIDI messages

• Power Management: The USB-C input powers the system, while the voltage regulator steps down from 5V to 3.3V for stable MCU operation

• Output: Sends real-time MIDI signals to a computer or synthesizer for sound generation

Components

1. Sensing: Velocity Detection

• Mechanical key switch

• Tactile switch used for velocity (time-difference) detection

2. Compute: ESP32-S2-Solo-N4

• Sufficient GPIO pins for key matrix scanning

• Native USB-MIDI support

• Low-power, cost-effective microcontroller

3. Power: 5V-3.3V LDO Regulator

• Efficient and clean power delivery

• Provides stable 3.3V supply for MCU and peripherals

Component details

1. Sensing: Velocity Detection

Schematics

Layout & Board Dimensions

Microcontroller and Power Input Section

• The ESP32-S2-SOLO-N4 microcontroller is the core processing unit that scans the key matrix and handles MIDI signal generation.

• The USB-C connector provides both power and communication with the computer.

• A voltage regulator (5V → 3.3V) ensures stable power for the ESP32 and logic-level components

Key Matrix Section

• The 4×6 key matrix consists of 24 keys (switches S1–S24), each connected through row and column traces for efficient scanning.

• This layout reduces the number of GPIO pins needed by allowing the ESP32 to detect key presses through row-column combinations instead of individual wires.

• Each key is associated with a diode to prevent ghosting and ensure accurate key detection when multiple keys are pressed simultaneously.

• The layout is optimized for signal integrity and short trace lengths, minimizing electrical noise in the keyboard circuit.

This PCB integrates compute, sensing, and power management in a single compact design for a functional MIDI keyboard prototype.

Physical Board

Wicki-Hayden Layout

Ease of Use: Layout keeps all different chord types in the same hand pattern, allowing the user to more easily compose their music