Introduction: Digital Synth VRA8-N for Arduino Uno

Made by ISGK Instruments



  • Monophonic Synthesizer (MIDI Sound Module) for Arduino Uno


  • Serial MIDI In (38.4 kbps)
  • PWM Audio Out (Pin 6, Unipolar, Line Level), PWM Rate: 62.5 kHz
  • Sampling Rate: 31.25 kHz, Bit Depth: 8 bits

Demo Audio


  • Exhibited in Maker Faire Tokyo 2018, Ogaki Mini Maker Faire 2018, Maker Faire Kyoto 2019

VRA8 Series

Step 1: Wiring

Required Hardware

  • A1: Arduino Uno
  • U1: 3.5 mm Audio Jack
  • R1: 100 ohm Resistor
  • R2: 100 ohm Resistor
  • C1: 100 nF Capacitor
  • Wires


  • See the image

Step 2: Software Installation

  1. Download Source code and extract it.
  2. Download Hairless MIDI<->Serial Bridge and extract it.
  3. Download loopMIDI and install it.

Step 3: Start Synthesizer

Explanation for Windows

  1. Write DigitalSynthVRA8N.ino to Arduino Uno and quit Arduino IDE.
    • CAUTION: We strongly recommend Arduino IDE 1.8.5, more precisely Arduino AVR Boards core 1.6.20
  2. Start loopMIDI.
  3. Start hairless-midiserial.exe (Hairless MIDI<->Serial Bridge).
    • Select Arduino Uno (COM*) on Serial Port.
    • Select loopMIDI Port on MIDI In.
    • Set [File] > [Preferences] > [Baud rate] to 38400 bps.
  4. Open vra8-n-ctrl.html (VRA8-N CTRL) with Google Chrome.
    • Select a MIDI controller on MIDI IN (if you have it).
    • Select loopMIDI Port on MIDI OUT.
  5. Click (or touch) the Software Keyboard, and you can hear the sound.