MIDI Theremin

Theory of operation

Converts VL53L1X time-of-flight distance sensor readings into MIDI Control Change messages. Perfect for creating interactive MIDI controllers, gesture-based music interfaces, or experimental instruments.

By positioning the two ToF sensors as the Theremin's antennas, you can create a controller perfect for complimentary parameters such as Frequency and Resonance of a Lowpass Filter.

Features

• Support for multiple VL53L1X distance sensors
• Real-time distance to MIDI CC conversion
• Value filtering for stable readings
• Automatic sensor address management
• Configurable distance range (10mm - 300mm by default)
• Value change detection to minimize MIDI traffic

Hardware Requirements

• Any CircuitPython compatible board (tested with Raspberry Pi Pico)
• One or more VL53L1X Time-of-Flight distance sensors

Pin Connections

Default configuration:

• SDA: GP4
• SCL: GP5
• XSHUT1: GP2
• XSHUT2: GP3

Software Dependencies

Required CircuitPython libraries:

• adafruit_vl53l1x
• adafruit_midi
• busio
• usb_midi

Installation

1. Install CircuitPython on your board
2. Copy the required libraries to the lib folder on your CircuitPython device or use circup
3. Connect your distance sensors following the pin configuration
4. Copy code.py to your CircuitPython device

Usage

The device will appear as a USB MIDI device when connected to your computer. Each sensor sends MIDI CC messages on different control numbers:

• Sensor 1: CC 20
• Sensor 2: CC 21 (and so on...)

The distance values are mapped as follows:

• Minimum distance (10mm) = MIDI value 0
• Maximum distance (300mm) = MIDI value 127

Configuration

You can modify these parameters in the code:

• MIN_DISTANCE and MAX_DISTANCE in the DistanceSensor class
• ALPHA value in ValueFilter class for smoothing (default: 0.3)
• MIDI CC numbers in SensorArray.update()
• I2C and XSHUT pins in SensorArray.__init__()

Class Structure

• ValueFilter: Implements Exponential Moving Average Filtering
• MIDIController: Handles MIDI communication
• DistanceSensor: Manages individual sensor operations
• SensorArray: Coordinates multiple sensors and MIDI output

Troubleshooting I2C errors:

• Verify wire connections
• Check for address conflicts
• Ensure proper power supply

Contributing

Feel free to submit issues and enhancement requests!

License

This project is released under the MIT License. See LICENSE file for details.