Digital Synth VRA8-M for Arduino Uno

Made by ISGK Instruments

• https://github.com/risgk/digital-synth-vra8-m

Concept

• Monophonic Synthesizer (MIDI Sound Module) for Arduino Uno

Features

• Serial MIDI In (38400 bps), PWM Audio Out (Pin 6), PWM Rate: 62500 Hz
• Sampling Rate: 15625 Hz, Bit Depth: 8 bits

Demo Audio

• https://soundcloud.com/risgk/digital-synth-vra8-m-100-demo-recording-from-arduino

Notes

• Exhibited in Maker Faire Tokyo 2015

Required Hardware

• Arduino Uno
• 3.5 mm Audio Jack (or Speaker)
• 330 (150 or more) ohm Resistor
  
• Wires

Wiring

• Audio Jack L or R (or Speaker +) ---- Resistor ---- Arduino Uno Digital Pin 6
• Audio Jack GND (or Speaker -) ---- Arduino Uno GND Pin
• PC ----[USB Cable]---- Arduino Uno

Additional Notes

• We recommend adding a RC filter circuit to reduce PWM ripples
• A cutoff frequency 10.6 kHz (R: 150 ohm, C: 0.1 uF) works well
• Ref. http://sim.okawa-denshi.jp/en/CRlowkeisan.htm
• Ref. http://sim.okawa-denshi.jp/en/CRlowkeisan.htm

1. Download Source code and extract it.
   • From https://github.com/risgk/digital-synth-vra8-m
2. Download Hairless MIDI<->Serial Bridge and extract it.
   • From http://projectgus.github.io/hairless-midiserial/
3. Download loopMIDI and install it.
   • From http://www.tobias-erichsen.de/software/loopmidi.html

Explanation for Windows

1. Write DigitalSynthVRA8M.ino to Arduino Uno and quit Arduino IDE.
2. Start loopMIDI.
3. Start hairless-midiserial.exe (Hairless MIDI<->Serial Bridge).
   • Set [File] > [Preferences] > [Baud rate] to 38400 bps.
   • Select Arduino Uno (COM*) on Serial Port.
   • Select loopMIDI Port on MIDI In.
4. Open vra8-m-ctrl.html (VRA8-M CTRL) with Google Chrome.
   
   • Select loopMIDI Port on MIDI OUT.
   • Select a MIDI controller on MIDI IN (if you have it).
5. Click (or touch) the Software Keyboard, and you can hear the sound.