Beat Boi

4-Track Drum Machine | Teensy 4.1, C++, Laser Cutting | 2024

Euclidean step sequencer and sample-based drum machine with lo-fi effects. Features modal "rules of 4" interface—4 encoders controlling 4 tracks across 7 pages accessed via 4 mechanical keys—with minimal 8x16 LED matrix feedback using spatial glyphs instead of precise readouts.

Interface & Features

Built on Teensy 4.1 with custom firmware using Teensy Audio Library for sample playback and DSP.

Signal path: 4 sample tracks → mixer → 24dB/oct ladder filter + bitcrusher → reverb → PCM5102A I2S DAC.

Seven control pages follow the signal path:

Sequencer (16-step grid with cursor control)

Euclidean Steps (variable sequence lengths for polyrhythmic phasing)

Sample (16 samples per track), Tune (playback rate/pitch control),

BitCrush (filter + distortion),

Reverb (size/damping)

Mix (4-track volume with visual feedback). Master encoder controls tempo and dry/wet mixing across pages.

LED matrix displays control-specific glyphs designed for building spatial memory rather than showing precise values—users learn the interface through muscle memory and visual impressions.

Hardware & Enclosure

All components (4 encoders, 4 mechanical keys, master encoder, LED matrix) use Feather boards with I2S interface, daisy-chained via STEMMA cables to minimize soldering. Prototyped in cardboard fingerjoint box before final laser-cut acrylic enclosure—deep purple acrylic with contrasting orange encoders, M2 screw assembly. Mechanical keys mounted on acrylic standoff with laser-cut washer stacks for comfortable inset positioning.

Early prototyping on Arduino Uno with Mozzi library validated sequencer logic before migrating to Teensy for processing headroom and audio quality.