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Hardware Setup Guide

Bill of Materials

Item Purpose Approx Cost Source
Raspberry Pi 5 (4GB) Central compute node ~€80 rs-online.com
4x MEMS mics (ICS-43434 or SPH0645) on breakout boards Acoustic array ~€40 Pimoroni / Adafruit
USB Audio Interface (2ch: Focusrite Scarlett Solo) Clean 2-channel audio capture ~€80 Thomann
USB Audio Interface (4ch: Behringer UMC204HD) Clean 4-channel audio capture ~€80 Thomann
2x Cardioid microphones (Behringer C-2 matched pair, or 2x Rode M3 at ~€70 each) High-fidelity comparison channels ~€55 Thomann
Tripod + mic stand Array mounting at fixed height (1.2m) ~€30 Amazon
Laser distance measurer Precise drone distance marking ~€30 Amazon
Measuring tape 50m Distance markers ~€15 Hardware store
Pi Camera Module 3 Visual confirmation / timestamp sync ~€30 RS
MicroSD 64GB Class 10 Recording storage ~€15 Amazon
3D-printed tetrahedral array mount 4-mic spatial geometry (5cm spacing) ~€5 Printables.com
Portable power bank 20,000mAh Field power ~€40 Amazon
TI AWR1843BOOST (optional) 77GHz mmWave radar ~€300-400 Mouser / TI

Total: ~€400-500 (without radar), ~€700-900 (with radar)

Microphone Array

Tetrahedral Configuration

The 4-mic array uses a regular tetrahedron with ~5cm edge length. This provides 3D spatial resolution for direction-of-arrival estimation.

        Mic 1 (top)
       /    |    \
      /     |     \
   Mic 2  Mic 3  Mic 4  (base triangle)

Mount height: 1.2m on tripod.

Wiring (MEMS I2S mics to Pi)

For ICS-43434 breakout boards:

Mic Pin Pi GPIO
VDD 3.3V
GND GND
SCK GPIO 18 (PCM_CLK)
WS GPIO 19 (PCM_FS)
SD GPIO 20 (PCM_DIN)

For multi-mic I2S, use L/R select pins to multiplex. Or use the USB audio interface approach below.

USB Audio Interface Approach (Recommended)

Connect MEMS mics via preamp circuits to the USB audio interface inputs. This gives cleaner ADC conversion and works on both Pi and Mac.

2-channel setup (Focusrite Scarlett Solo):

  • Input 1 (XLR, mic preamp): Cardioid reference mic or MEMS via preamp
  • Input 2 (1/4" instrument/line): Requires external preamp for MEMS mic
  • Note: Only input 1 has a mic preamp with phantom power

4-channel setup (Behringer UMC204HD):

  • Input 1-2 (XLR/TRS combo, mic preamps): MEMS mics via preamp or cardioid reference mics
  • Input 3-4 (TRS, line-level only): Require external mic preamps for MEMS mics
  • Note: Inputs 3-4 have no mic preamp gain or phantom power

Radar Setup (Optional)

TI AWR1843BOOST

  1. Flash the out-of-box demo firmware using UniFlash
  2. Connect CLI port (typically /dev/ttyACM0 on Pi, /dev/cu.usbmodem* on Mac)
  3. Connect data port (typically /dev/ttyACM1)
  4. The software auto-configures for drone detection profile

Radar + Acoustic Sync

Both systems use system clock timestamps. For tight sync:

  • Start radar and audio capture within the same Python process
  • Log timestamps in both data streams
  • Post-processing aligns by nearest timestamp

Field Setup Checklist

  • Array mounted at 1.2m on tripod
  • Distance markers placed at 25m, 50m, 75m, 100m, 150m, 200m
  • Ambient noise measured (SPL meter app)
  • Wind speed noted (Beaufort scale)
  • Temperature noted
  • GPS coordinates logged
  • Test recording made and verified
  • Battery levels checked (Pi power bank, drone batteries)
  • Pi Camera recording visual reference