ESP32 Sound Direction Demo

Dual INMP441 microphones on an ESP32 using ESP-IDF v6. The firmware captures stereo I2S audio, estimates approximate SPL for each mic, and computes a rough arrival angle from inter-mic delay.

Current firmware behavior:

• 16 kHz stereo capture
• GPIO 2 LED turns on when either mic exceeds the SPL threshold
• CSV metrics over UART
• Optional Wi-Fi UDP forwarding for logs and metrics
• Optional browser monitor in web_monitor/

Hardware

Both microphones share clocks and the same SD data line.

Mic	INMP441 Pin	ESP32 Pin
Left mic	SD / DOUT	GPIO 19
Left mic	WS / LRCLK	GPIO 32
Left mic	SCK / BCLK	GPIO 33
Left mic	L/R	GND
Right mic	SD / DOUT	GPIO 19
Right mic	WS / LRCLK	GPIO 32
Right mic	SCK / BCLK	GPIO 33
Right mic	L/R	3V3
Both mics	VDD	3V3
Both mics	GND	GND

One mic must be strapped left and the other right when they share the same SD line.

Build

idf.py build
idf.py flash monitor

Serial Output

The app prints a CSV header followed by one metrics row about every 100 ms.

Current columns:

dBSPL1,dBSPL2,level_diff_db,corr_peak,delay_samples,delay_samples_frac,delay_us,angle_deg,delay_confidence,load_core0,load_core1,min_free_heap

When the input is too quiet for direction estimation, the direction-related fields are emitted as nan.

Browser Monitor

The repository includes a small local monitor in web_monitor/ for the angle_deg stream.

Run it with:

python3 web_monitor/serve.py

Then open http://127.0.0.1:8765 in Chrome or Edge and choose:

• Connect Serial to read UART directly with Web Serial
• Connect Wi-Fi to read UDP-forwarded metrics through the local bridge

By default the bridge listens for metrics on UDP port 30501.

Optional Wi-Fi Forwarding

To forward logs and CSV metrics over Wi-Fi:

1. Copy main/include/secrets_example.h to main/include/secrets.h.
2. Fill in WIFI_SSID, WIFI_PASSWORD, and UDP_DEST_IP.
3. Build with Wi-Fi forwarding enabled:

idf.py -DENABLE_WIFI_LOGGING=1 build

Defaults:

• Log UDP port: 30500
• Metrics UDP port: 30501

You can override the ports at build time:

idf.py -DENABLE_WIFI_LOGGING=1 -DUDP_LOG_PORT=30500 -DUDP_METRICS_PORT=30501 build

main/include/secrets.h is gitignored and should not be committed.

License

MIT. See LICENSE.