Beat Boi is a 4-track sample-based drum machine with a euclidean step sequencer, built around a Teensy 4.1 microcontroller. It features a model interface with 4 encoders control 4 tracks, and 4 mechanical keys switch between control modalities - a common pattern in digital synthesizers that packs a lot of parameters into a small form factor while still letting the user build muscle memory over time. Feedback comes from an 8x16 LED matrix using glyphs rather than precise readouts, just enough visual impression to learn the controls without distracting from playing.
Tech Overview
The OS is built on a Teensy 4.1 with the Teensy Audio Library handling sample playback and DSP. Each encoder and mechanical key runs on its own Feather board over I2S, daisy-chained via STEMMA cables to avoid soldering each input individually. The zero-glue, friction-hold enclosure was designed in Rhino and fabricated using laser cut acrylic with 3D printed binding pieces. The friction hold allows for the unit to be disassembled and updated without glue or screws.
Signal path:
- 4 sample tracks
- Mixer
- Filter / bitcrusher pass
- Reverb pass
- PCM5102A I2S DAC
The 7 control pages roughly follow the signal path:
- Sequencer: 16-step grid per track, encoder-driven cursor, master encoder sets tempo
- Euclidean Steps: per-track sequence length (1 to 16 steps) for phasing polyrhythms; master encoder resets total length
- Sample: 16 samples per track; master encoder swaps all samples at once
- Tune: per-track playback rate/pitch; master encoder pitches everything for rise/fall effects
- BitCrush: 24dB/oct ladder filter into a bitcrusher, for chiptune-style lo-fi distortion
- Reverb: size/decay and damping
- Mix: 4-track volume with visual feedback, master volume on the master encoder
