Hardware

Detector

Component	Notes
Heltec WiFi LoRa 32 V3 / V4	ESP32-S3 + SX1262 on-board
ICS-43434 or INMP441 I2S MEMS microphone	3.3 V, L/R → GND (left channel)

Wiring (ICS-43434 / INMP441 → Heltec V3 / V4)

Mic pin	GPIO	Function
VDD	3.3V	Power
GND	GND	Ground
SCK	4	I2S bit clock (BCLK)
WS	5	I2S word select (LRCLK)
SD	6	I2S data input (DIN)
L/R	GND	Left channel select

ICS-43434 vs INMP441

Both mics share the same pinout and I2S protocol, so they're drop-in interchangeable on this wiring. ICS-43434 is preferred for drone detection (higher sensitivity at −38 dBFS, 130 dB SPL AOP); INMP441 is cheaper and easier to source, but has lower sensitivity (−26 dBFS) and a 120 dB SPL AOP, which can clip on close, loud sources.

Battery monitoring (optional)

Heltec V3 / V4 ship with an on-board LiPo jack, charger, and a resistor divider that taps VBAT onto GPIO1 (ADC1_CH0), gated by GPIO37 (ADC_Ctrl, active low). The firmware drives the gate low only during a ~2 ms measurement window on every LoRa TX, so the divider's ~100 µA current drain is effectively eliminated between reads.

No extra wiring is required — plug a 1S LiPo into the JST connector and the detector reports battery_v (plus a low-battery flag below 3.4 V) in every telemetry packet. Boards without this divider can simply leave BOARD_HAS_VBAT at 0 in pin_config.h and the battery module compiles down to no-ops (readings are reported as 0 V).

Wired Detector (Ethernet/PoE)

Component	Notes
LILYGO T-ETH-Lite S3	ESP32-S3 + W5500 Ethernet on-board, optional PoE expansion
ICS-43434 or INMP441 I2S MEMS microphone	3.3 V, L/R → GND (left channel)

Wiring (ICS-43434 / INMP441 → T-ETH-Lite S3)

Mic pin	GPIO	Function
VDD	3.3V	Power
GND	GND	Ground
SCK	38	I2S bit clock (BCLK)
WS	39	I2S word select (LRCLK)
SD	40	I2S data input (DIN)
L/R	GND	Left channel select

See the ICS-43434 vs INMP441 note above for sensitivity / AOP differences when choosing between the two mics.

Tip

GPIO 38/39/40 are on the extension headers of the T-ETH-Lite S3. These pins avoid conflicts with the on-board W5500 Ethernet (GPIO 9–14) and the SD card slot (GPIO 5/6/7/42, see below).

On-board microSD slot

The T-ETH-Lite S3 routes its TF slot to a 4-pin SPI footprint (not SDMMC), and the firmware drives it through the FATFS SDSPI driver on SPI3_HOST so it doesn't conflict with W5500 on SPI2_HOST.

Slot pin	GPIO	Function
MISO	5	SDSPI MISO
MOSI	6	SDSPI MOSI
SCK	7	SDSPI clock
CS	42	SDSPI chip select (SD's D3 line in 4-bit mode)

Use a FAT32-formatted card ≤ 32 GB (SDHC). SDXC cards are typically pre-formatted exFAT, which the IDF SDSPI mount won't accept — reformat to FAT32 first. Don't pull the card while a recording is in progress — wait for the REC stop: …_alarm.wav dur=…s log line on the serial console so the FATFS directory entry is committed.

BOOT button (push-to-talk)

The on-board BOOT button (GPIO 0, the small button beside the RST button) doubles as a push-to-talk capture trigger when BATEAR_TF_MANUAL_ENABLE=y. Press = start recording, release = stop. The button has internal pull-up enabled at runtime; the strap reading at next reset is unaffected so idf.py flash keeps working unattended.

The wired detector connects directly to your network via Ethernet (RJ45). If you use a PoE expansion board, power and data come through a single cable — ideal for permanent outdoor installations.

IP addressing

By default the wired detector uses DHCP. For fixed installations you can assign a static IP via the serial console (set eth_ip 192.168.1.50) or at build time in sdkconfig.wired_detector. See Configuration → Ethernet static IP for details.

OTA firmware updates

The wired detector includes a built-in REST API (port 8080) that supports over-the-air firmware updates with automatic rollback. Upload a new binary with curl -X POST --data-binary @firmware.bin http://<ip>:8080/api/ota. See the REST API reference for all endpoints.

Gateway

Component	Notes
Heltec WiFi LoRa 32 V3 / V4	Uses on-board SX1262, SSD1306 OLED, and LED

No external wiring needed — everything is on-board.