Arduino Sequencer

An Arduino-based control voltage sequencer for analog synthesizers. Generates precise 1V per octave control voltages using PWM output + filtering.

Features

• Generates 1V per octave control voltages
• 20 kHz PWM frequency (inaudible)
• Cycles through 5 octaves automatically
• Built with PlatformIO for Arduino Uno

Hardware & Circuit

I used an Arduino Uno R3 with the following connections:

• PWM output on pin 9
• GND connected to the circuit ground
• Vin connected to the positive supply (12V)

The PWM signal is converted to clean analog CV using:

1. Two cascaded RC low-pass filters (10kΩ + 100nF each) to smooth the PWM
2. Op-amp buffer for clean output and current drive capability (positive supply at 12V, negative at GND)

Getting Started with PlatformIO

This project uses PlatformIO for development and deployment.

1. Install PlatformIO (VS Code extension recommended)
2. Connect your Arduino Uno via USB
3. Use the PlatformIO interface to build and upload, or run pio run --target upload from the command line

For detailed instructions, see the PlatformIO Quick Start Guide.

Usage

Currently runs an automatic sequence cycling through musical notes with appropriate control voltages based on the 1V per octave standard.

Future Ideas

• MIDI file support - Load and play back MIDI sequences
• Real-time MIDI input - Live MIDI control and sequencing
• Standalone sequence editing - Ability to create and modify sequences in standalone mode with some knobs/buttons and a display