MIDIfy — DIY MIDI DJ Controller

A custom-built MIDI DJ controller using an Arduino Uno and repurposed hard disk drive (HDD) components. Physical inputs — buttons, potentiometers, and a scratch mechanism — are converted into MIDI signals that control a DAW in real time.

Built as a group academic project during B.Sc. Electronics at Christ University.

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What it does

• 3 push buttons send MIDI Note ON/OFF messages — mapped to cue points or pads in Ableton Live
• 2 potentiometers/sliders send MIDI Control Change (CC) messages — mapped to volume, pitch, or effects
• An HDD platter mechanism simulates vinyl scratching using repurposed disk components
• All inputs are debounced and noise-filtered for stable, reliable MIDI output

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Hardware used

Component	Purpose
Arduino Uno (ATmega328)	Microcontroller — reads inputs and sends MIDI
3x Push buttons	Trigger MIDI notes (cue points, pads)
2x Potentiometers / sliders	Send MIDI CC for faders and knobs
HDD platter + arm	Scratch mechanism — simulates vinyl
Resistors	Pull-up/pull-down for button circuits

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Software & Libraries

• Arduino IDE
• Hairless MIDI — bridges Arduino serial to MIDI
• loopMIDI — virtual MIDI port on Windows
• Ableton Live 11 — DAW used for mapping and performance
• MIDI.h — Arduino MIDI library
• ResponsiveAnalogRead — smooths potentiometer noise

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How it works

Physical input
      │
      ▼
Arduino reads pin (digital or analog)
      │
      ├── Button pressed?  →  Send MIDI Note ON  (velocity 127)
      │   Button released? →  Send MIDI Note OFF (velocity 0)
      │
      └── Pot moved?       →  Map raw value (0–1023) to MIDI (0–127)
                               Send MIDI Control Change (CC)
      │
      ▼
Serial → Hairless MIDI → loopMIDI → Ableton Live

Potentiometers are smoothed using ResponsiveAnalogRead to eliminate jitter. A movement threshold (varThreshold = 20) and a timeout window (TIMEOUT = 300ms) ensure CC messages are only sent when the pot is genuinely being moved.

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Pin mapping

Pin	Component	MIDI message
D2	Button 1	Note 36 (C2) ON/OFF
D3	Button 2	Note 37 (C#2) ON/OFF
D4	Button 3	Note 38 (D2) ON/OFF
A0	Potentiometer 1	CC 1 (0–127)
A1	Potentiometer 2	CC 2 (0–127)

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How to set up and run

1. Install the Arduino IDE and required libraries (MIDI.h, ResponsiveAnalogRead)
2. Open midify.ino and set #define ATMEGA328 at the top to target Arduino Uno
3. Upload the sketch to your Arduino Uno
4. Open Hairless MIDI — select your Arduino's COM port as the serial input
5. Open loopMIDI — create a virtual MIDI port
6. In Hairless MIDI, route output to the loopMIDI port
7. Open Ableton Live → go to Preferences → MIDI → enable the loopMIDI port
8. Use MIDI Map mode in Ableton to assign buttons and pots to controls
9. Play

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To customise

• Change note = 36 to shift which MIDI notes the buttons trigger
• Change cc = 1 to shift which CC numbers the pots control
• Adjust debounceDelay if buttons feel unresponsive or double-trigger
• Adjust varThreshold and snapMultiplier to tune pot sensitivity

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Project context

Built as part of a B.Sc. Electronics group project at Christ University (2023–2024). The goal was to demonstrate hardware-software integration — combining circuit design, microcontroller programming, and real-world MIDI protocol to build a functional musical instrument.

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Skills demonstrated

Arduino C++ Embedded Systems MIDI Protocol Analog Signal Processing Hardware-Software Integration Circuit Design Ableton Live