Connecting an Arduino directly to a Digital Audio Workstation (DAW) opens up a world of custom MIDI controllers, DIY instruments, and unique performance interfaces. While some newer boards support native USB-MIDI, classic boards like the Arduino Uno and Nano communicate via standard serial data. To bridge the gap between serial messages and the MIDI data your DAW understands, you need a software translator.
This guide will walk you through using the Hairless MIDI to Serial Bridge alongside a virtual MIDI loopback port to connect your Arduino to any major DAW. The Software Toolkit
To get started, you need to download and install three essential components:
The Arduino IDE: Used to write and upload the code to your micro-controller.
Hairless MIDI to Serial Bridge: The lightweight open-source application that receives Arduino serial data and forwards it as standard MIDI.
A Virtual MIDI Loopback Port: Hairless needs a destination to send its MIDI data. Windows users: Download loopMIDI by Tobias Erichsen.
macOS users: No download needed. You can use the built-in IAC Driver found inside the Audio MIDI Setup utility. Step 1: Create a Virtual MIDI Port
Before launching the bridge software, you must create a virtual highway for your MIDI data.
On Windows (loopMIDI): Open the application, click the + button in the bottom left corner to create a new port, and name it something recognizable like “Arduino_MIDI”. Keep loopMIDI running in the background.
On macOS (IAC Driver): Open Finder, navigate to Applications > Utilities, and open Audio MIDI Setup. Go to Window > Show MIDI Studio. Double-click the IAC Driver icon, check the box labeled Device is online, and ensure at least one bus is active. Step 2: Code and Upload the Arduino Sketch
Your Arduino must send data over the serial port at a specific baud rate (speed) that matches the setting you will use in Hairless. Standard MIDI runs at 31,250 bps, but Hairless allows you to use standard, faster USB speeds like 115,200 bps for lower latency.
Here is a simple example sketch that sends a repetitive MIDI note. Upload this to your Arduino:
// Simple Arduino MIDI Serial Example void setup() { // Initialize serial communication at 115200 baud Serial.begin(115200); } void loop() { // MIDI Note On: 0x90 = Note On (Channel 1), 60 = Middle C, 127 = Velocity MIDI_TX(0x90, 60, 127); delay(500); // MIDI Note Off: 0x80 = Note Off (Channel 1), 60 = Middle C, 0 = Velocity MIDI_TX(0x80, 60, 0); delay(500); } void MIDI_TX(byte MESSAGE, byte PITCH, byte VELOCITY) { Serial.write(MESSAGE); Serial.write(PITCH); Serial.write(VELOCITY); } Use code with caution. Step 3: Configure Hairless MIDI to Serial Bridge
With your Arduino plugged into your computer and running the sketch, open Hairless MIDI to Serial Bridge.
Serial Port: Select your Arduino’s COM or USB port from the dropdown menu.
MIDI Out: Select the virtual port you created in Step 1 (e.g., “Arduino_MIDI” or “IAC Driver Bus 1”).
MIDI In: If you want your DAW to send data back to the Arduino (like lighting up LEDs), select the same virtual port here.
Preferences: Go to File > Preferences (or Hairless > Preferences on Mac) and ensure the Baud Rate matches your Arduino code exactly (115200). Connect: Check the box next to Serial <-> MIDI Bridge On.
If everything is working correctly, the green indicator lights in Hairless will flash rapidly, showing that serial data is successfully converting into MIDI data. Step 4: Route the MIDI inside your DAW
The final step is configuring your DAW (such as Ableton Live, FL Studio, Logic Pro, or Reaper) to listen to your new virtual port.
Open your DAW’s Preferences or Settings menu and look for the MIDI tab.
Locate your virtual port name (“Arduino_MIDI” or “IAC Driver”) in the input list.
Enable Track (to play instruments) and Remote (to map knobs and sliders) for that input.
Load a virtual instrument track, arm it for recording, and you should hear the Middle C note triggered by your Arduino code. Troubleshooting Tips
“Serial port is busy” Error: Hairless and the Arduino IDE serial monitor cannot use the COM port at the same time. Always uncheck the “Bridge On” box in Hairless before trying to upload new code from the Arduino IDE.
Garbled Data / Red Lights: If Hairless throws errors or logs weird characters, double-check that the Serial.begin() speed in your Arduino code matches the Baud Rate setting in the Hairless preferences.
Latency Issues: If there is a noticeable delay between pressing a physical button on your Arduino and hearing the sound, ensure your DAW is using an ASIO audio driver (on Windows) and reduce your audio buffer size to 128 or 256 samples.
By mastering the Hairless bridge workflow, you bypass the need for expensive hardware or complex firmware flashing, giving you a fast, reliable method to test and deploy custom MIDI controllers. To help you build out your project, let me know: