Untouchable LIMiTS

Looper Instrument & Metronome inside Theremin Synthesizer is a musical instrument that combines the functionality of a synthesizer, an optical-sensor-based theremin, and a loop station, all processed on an ESP32-S3 microcontroller.

• What it does: It generates real-time audio waveforms (sine, square, triangle, sawtooth) that the user can modulate. The pitch (frequency) is controlled either “in the air” by moving a hand over a ToF laser sensor, or via a DIY capacitive touch keyboard. The device allows recording a multi-bar audio sequence and playing it back in a continuous loop, offering the ability to play “over” your own recording (overdubbing).
• The starting idea: The desire to build an electronic instrument that does not rely on expensive physical keyboards, while integrating a “loop pedal” directly into the internal memory to be able to have a jam session with yourself.

The project is structured around the ESP32-S3-WROOM-1 (N16R8) microcontroller, which runs the audio synthesis on one processor core and the user interface/metronome on the other core, ensuring zero-latency performance.

System Architecture (Main Blocks):

• Input & Navigation Module: An I2C OLED display and an EC11 rotary encoder form the graphical user interface for selecting waveforms and ADSR envelope settings.
• Sensory Module (The Instrument):
  • A VL53L1X Time-of-Flight sensor communicates via I2C to measure hand distance with millimeter precision, mapping the data to a musical scale.
  • A capacitive keyboard (aluminum foil strips) connects directly to the ESP32's internal hardware touch pins.
• Looping: Tactile push buttons trigger audio recording directly into the 8MB PSRAM.
• Metronome: An independent active buzzer with volume and bpm configurable. Being separate from the sound generating loop it won't interfere with the recording.
• Audio Output Module (The “Hacky” DAC): The digital signal (PDM/PWM) generated by the ESP32 passes through a 1st-order hardware Low-Pass RC filter for smoothing. It is then amplified by an LM386 module and routed directly to a pair of wired headphones via a modified 3.5mm jack splitter.

Bill of Materials (BoM):

• 1x ESP32-S3-DevKitC-1 (N16R8): The main microcontroller (16MB Flash, 8MB PSRAM for the audio buffer).
• 1x VL53L1X Time-of-Flight Sensor: For the Theremin functionality (I2C).
• 1x 0.96” OLED Display: For the system menu (I2C).
• 1x EC11 Rotary Encoder: With built-in push button, for menu navigation.
• 1x LM386 Audio Amplifier Module: To amplify the filtered signal for headphones.
• 3x 10k Linear Potentiometers (B10K): For dynamic volume control and LFO/filter adjustments.
• 1x Passive Buzzer: For the integrated dual-core metronome.
• 3-4x Tactile Push Buttons (Momentary): 12x12mm, for loop triggering and UI.
• Passive Components (RC Filter & Decoupling):
  • 1x `104` Ceramic Capacitor (0.1µF)
  • 1x `475` Ceramic Capacitor (4.7µF) - For power supply stabilization on the breadboard.
  • Resistors (220Ω - 330Ω for the audio filter, 1kΩ for the buzzer).
• 1x 3.5mm Audio Jack Splitter Cable: to connect headphones to the breadboard without destroying the original headphone plug.
• DIY Materials: Aluminum foil and cardboard for the capacitive keyboard.
• Miscellaneous: Breadboards (minimum 2 tied together), Dupont jumper wires (M-M, M-F)

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