qtalker---/firmware/esp32p4-sensor-node

Quantumancy ESP32-P4 Sensor Node

Firmware for the paired hardware sensor node described in docs/superpowers/specs/2026-07-23-esp32-sensor-node-design.md ("Workstream I — firmware, ESP-IDF C — core sensor node"). Real ESP-IDF C (FreeRTOS-based), not Arduino, not pseudocode. Connects to the seeker's home Wi-Fi, samples a small set of sensors, and POSTs readings to the Quantumancy backend's POST /api/device/telemetry endpoint, which feeds them into the séance's live anomaly-detection pipeline as a sixth signal source alongside wire/evp/radio/emf.

Honesty policy — READ THIS FIRST

This app's whole ethos is "real signal processing on real data, and it says so when something is unverified."

Nobody working on this had physical ESP32-P4 hardware, a BME280, or an LD2410 module to flash and test against. Everything in this directory is real, structurally-correct ESP-IDF C, written against ESP-IDF's documented APIs and each sensor's public datasheet/protocol documentation, and reasoned about carefully — but it has never been compiled with a real ESP-IDF toolchain, never been flashed, and never talked to real hardware. Treat every claim below as "should work, per the docs" rather than "confirmed working." See What's verified vs. not for the specific, itemized breakdown — this mirrors the same convention frontend/src/lib/sdr.ts's HARDWARE PASS REQUIRED header comment uses elsewhere in this repo.

Directory layout

firmware/esp32p4-sensor-node/
├── CMakeLists.txt              top-level ESP-IDF project file
├── sdkconfig.defaults          seed config (idf.py generates the real sdkconfig)
├── README.md                   this file
├── components/                 reserved for Workstream J (RTL-SDR), empty here
└── main/
    ├── CMakeLists.txt          component registration
    ├── app_main.c              entry point / boot sequence
    ├── device_config.h.example template you copy to device_config.h
    ├── wifi_manager.{h,c}      Wi-Fi station mode connect/reconnect
    ├── telemetry_client.{h,c}  HTTP POST task -> /api/device/telemetry
    ├── sensor_driver.h         the sensor_driver_t registry interface
    ├── sensor_registry.{h,c}   the concrete list of compiled-in drivers
    ├── bme280.{h,c}            temperature/humidity/pressure over I2C
    └── ld2410.{h,c}            presence/distance over UART

Build instructions

Requires an ESP-IDF install (v5.3 or newer — ESP32-P4 target support landed around v5.2/5.3; this was written without a toolchain available to pin an exact tested version, see honesty section). With idf.py on your PATH (e.g. after sourcing ESP-IDF's export.sh):

cd firmware/esp32p4-sensor-node

# 1. Fill in your Wi-Fi + pairing details (see next section) — the build
#    will fail on a missing #include until you do this.
cp main/device_config.h.example main/device_config.h
$EDITOR main/device_config.h

# 2. Target and build.
idf.py set-target esp32p4
idf.py build

# 3. Flash + monitor (adjust the port for your machine).
idf.py -p /dev/ttyUSB0 flash monitor

Manual configuration (no provisioning UI — by design)

A full BLE/Wi-Fi-AP provisioning flow is explicitly out of scope for this spec (see the spec's "Explicitly out of scope" section). Instead, you hand-edit one header before building:

1. In the Quantumancy web app, sign in and create a device from your account (name + optional sensor-type hint). The backend shows you a raw pairing token exactly once — copy it immediately, it cannot be retrieved again (same one-time-secret convention as the site's session tokens).
2. cp main/device_config.h.example main/device_config.h
3. Edit main/device_config.h and fill in:
   • DEVICE_WIFI_SSID / DEVICE_WIFI_PASSWORD — your home Wi-Fi.
   • DEVICE_BACKEND_BASE_URL — the backend's base URL, no trailing slash.
   • DEVICE_PAIRING_TOKEN — the raw token from step 1.
   • DEVICE_REPORT_INTERVAL_SEC — optional, defaults to 15s.
4. main/device_config.h is listed in .gitignore — it will never be committed. Never put real credentials in device_config.h.example itself; that file is the template everyone else copies.

There is deliberately no other config path (no NVS-based captive portal, no BLE provisioning) in this build — see the spec's scope boundary.

What's verified vs. not

Structurally verified (reasoned through carefully against ESP-IDF's documented API surface and each sensor's public protocol docs; internally consistent; no known syntax errors or obviously-wrong API usage):

• Project skeleton (CMakeLists.txt × 2, sdkconfig.defaults, idf_component_register call) follows ESP-IDF's standard project layout.
• Wi-Fi station-mode connect/reconnect (wifi_manager.c) follows ESP-IDF's documented event-driven pattern (WIFI_EVENT/IP_EVENT handlers + EventGroupHandle_t), extended with an exponential-backoff reconnect timer instead of giving up after N tries.
• HTTP client (telemetry_client.c) builds the exact JSON shape the spec's contract defines and POSTs it via esp_http_client with Authorization: Bearer <token> and Content-Type: application/json.
• BME280 driver (bme280.c): register map and the double-precision compensation formulas are transcribed from Bosch's public BME280 datasheet (rev 1.23, §4.2.2–4.2.3) — this is well-trodden, publicly documented territory, and the formulas are checkable line-by-line against the datasheet. Uses ESP-IDF's newer driver/i2c_master.h API (the current idiomatic choice; the older driver/i2c.h is being phased out).
• LD2410 driver (ld2410.c): UART frame envelope (header/footer magic bytes, length-prefixed payload) follows the shape consistently reported across public LD2410 protocol write-ups. The exact payload byte offsets for target state / distances / energies are the single least-certain piece of code in this entire firmware — see the detailed note in ld2410_parse_payload(). The driver defends itself with a head/tail marker sanity check (0xAA/0x55) and silently skips anything that doesn't match rather than reporting garbage, but that check catches gross corruption, not subtle off-by-one offset errors.
• Sensor driver registry (sensor_driver.h, sensor_registry.c): a sensor_driver_t { name, init, read } struct, a compile-time array of them, and generic init/collect functions that app_main.c and telemetry_client.c call without knowing which concrete sensors exist.

NOT verified — requires real hardware bring-up:

• idf.py build has never actually been run in this environment (no ESP-IDF toolchain installed here) — there could be a typo, a missing include, or an API signature mismatch against whatever exact ESP-IDF version you build with that only a real compile will surface.
• I2C timing/electricals: pull-up resistor values, bus speed headroom, cable length — none of this has been bench-tested.
• BME280 compensation formula correctness in practice: the math is transcribed carefully, but "matches the datasheet" and "produces a plausible number when this exact C runs on this exact silicon" are different claims until someone compares a real reading to a reference thermometer/barometer.
• LD2410 frame parsing, as above — verify against a logic analyzer capture or a known-good reference implementation (e.g. the ncmreynolds/ld2410 or iavorvel/MyLD2410 Arduino libraries, cross-checked) before trusting field values.
• Wi-Fi reconnect behavior under real-world conditions (router reboot, weak signal, captive portals) — the backoff logic is reasoned about, not soak-tested.
• HTTP client behavior against the real backend: TLS handshake against its actual certificate, real latency, real error responses. The sdkconfig.defaults enables mbedTLS's full certificate bundle for this, but that's untested against the live deploy.
• Timing/power: task stack sizes (telemetry_task's 8192 words, etc.) are reasonable guesses, not measured high-water-marks from a real run.
• The ESP32-P4-has-no-integrated-Wi-Fi caveat below — this is a real hardware architecture question, not just an untested detail.

Important hardware caveat: ESP32-P4 has no integrated Wi-Fi radio

The ESP32-P4 SoC (per Espressif's own published specs) has no built-in 2.4GHz radio. A real deployment needs one of:

• A companion Wi-Fi chip (e.g. ESP32-C6) wired to the P4 via SDIO or SPI, running Espressif's "esp-hosted" firmware/driver stack. Critically, esp-hosted presents the same esp_wifi/esp_netif API this firmware already uses — so wifi_manager.c should not need to change, only board wiring and sdkconfig (host-side esp-hosted config) would.
• Building this same code against a Wi-Fi-native target instead, e.g. idf.py set-target esp32s3 or esp32c6. The application code (wifi_manager.c, telemetry_client.c, the sensor drivers) is written against the standard API surface and doesn't reference P4-specific peripherals for anything except I2C/UART GPIO numbers, so it should be largely target-portable.

This wasn't in the original spec's framing but matters enough for a real build that it's called out here explicitly, in the honesty-policy spirit — better to flag a real hardware-architecture gap than let someone discover it after ordering a bare P4 dev board expecting it to just join Wi-Fi.

Wiring / pinout

BME280 (I2C) — temperature, humidity, pressure

Chosen as the concrete default sensor per the spec ("a common, well-documented sensor... pick this as the concrete default since no specific part number was given").

BME280 pin	Connects to
VCC	3V3
GND	GND
SDA	GPIO8 (BME280_I2C_SDA_GPIO)
SCL	GPIO9 (BME280_I2C_SCL_GPIO)
CSB	VCC (selects I2C mode, not SPI)
SDO	GND → I2C address 0x76 (default assumed; tie to VCC + change BME280_I2C_ADDR for 0x77)

GPIO numbers are #defines at the top of bme280.h — override them there (or via a future idf.py menuconfig entry) to match your actual wiring. 100kHz I2C clock by default (BME280_I2C_CLK_HZ); the part supports faster modes if your wiring/pull-ups support it.

LD2410 (UART) — presence, distance, motion

Chosen over a plain PIR — see the rationale in ld2410.h's header comment: the LD2410 reports moving-target and stationary-target distance and energy separately, not just a boolean, which is richer signal for the anomaly pipeline and better matches this app's "believable" ethos (it can distinguish "someone crossed the room" from "the sitter shifted in their chair" in a way a boolean PIR cannot). The tradeoff is a materially more complex protocol than a PIR's single GPIO pin — see the honesty note in What's verified vs. not about the LD2410 frame parser being the least-certain code in this firmware. If you'd rather start with a boolean PIR for a faster, more certain first bring-up, it fits the same sensor_driver_t interface — see Adding a new sensor below.

LD2410 pin	Connects to
VCC	5V (sensor front-end runs at 5V; confirm your board revision's UART logic level before wiring directly to a 3.3V-only UART pin)
GND	GND
TX	GPIO17 (LD2410_UART_RX_GPIO, ESP32 RX)
RX	GPIO18 (LD2410_UART_TX_GPIO, ESP32 TX)

Default UART settings: 256000 baud, 8N1 (module factory default), reporting in "basic" (non-engineering) mode. GPIO numbers and baud rate are #defines at the top of ld2410.h.

Sensor driver registry — the extensibility pattern

sensor_driver.h defines:

typedef struct {
    char sensor_type[SENSOR_READING_TYPE_MAXLEN];
    double value;
    char unit[SENSOR_READING_UNIT_MAXLEN];
    cJSON *metadata; // nullable; NULL serializes as {}
} sensor_reading_t;

typedef struct sensor_driver {
    const char *name;
    esp_err_t (*init)(void);
    esp_err_t (*read)(sensor_reading_t *out, size_t max_out, size_t *out_count);
} sensor_driver_t;

sensor_registry.c holds a compile-time array of these (currently BME280 and LD2410) and two generic functions, sensor_registry_init_all() and sensor_registry_collect(), that app_main.c and telemetry_client.c call without ever referencing bme280.c/ld2410.c directly. One driver failing init() or read() is logged and skipped — it doesn't take the whole node offline.

Adding a new sensor

1. Write main/my_sensor.h / main/my_sensor.c implementing init() and read() matching sensor_driver_t's function pointer signatures.
2. Add "my_sensor.c" to the SRCS list in main/CMakeLists.txt.
3. #include "my_sensor.h" in sensor_registry.c and add one line to the s_drivers[] array:

   { .name = "my_sensor", .init = my_sensor_init, .read = my_sensor_read },
   

Nothing in app_main.c, telemetry_client.c, or the main reporting loop's control flow needs to change — that's the whole point of this structure per the spec.

Backend contract this firmware targets

From the spec (binding, see the spec file for the authoritative version):

POST /api/device/telemetry
Authorization: Bearer <raw pairing token>
Content-Type: application/json

{
  "readings": [
    {"sensor_type": "presence", "value": 1, "unit": "bool", "metadata": {}},
    {"sensor_type": "temperature", "value": 21.4, "unit": "c", "metadata": {}},
    {"sensor_type": "humidity", "value": 47.2, "unit": "pct", "metadata": {}},
    {"sensor_type": "pressure", "value": 1013.2, "unit": "hpa", "metadata": {}}
  ]
}

This firmware's BME280 driver emits temperature/humidity/pressure exactly as shown; its LD2410 driver emits presence as a 0/1 boolean in value with the richer distance/energy data folded into metadata (moving_distance_cm, moving_energy, stationary_distance_cm, stationary_energy, detection_distance_cm, target_state).

Out of scope here

Per the spec: thermal camera support, a full BLE/Wi-Fi-AP provisioning UX, on-device spectrum analysis/FFT (the RTL-SDR module below forwards raw IQ upstream rather than analyzing on-device), and anything on the backend/frontend side (Workstreams G, H, K).

---

Workstream J — RTL-SDR experimental module

⚠️ This is the least certain part of the entire firmware build. Read this whole section before touching it.

What this is

A clearly-separated, opt-in, experimental module exploring USB-host communication with an RTL2832U-based SDR dongle over the ESP32-P4's native USB-OTG host controller (USB Host Library, usb_host.h — a real, documented capability of this specific chip, unlike most ESP32 variants). The idea, per the design spec: attach a cheap RTL-SDR dongle to the sensor node, treat "spirit radio scanning" as a hardware-backed mode instead of only a browser WebUSB feature.

Be honest about the real constraint (this is the spec's framing, and it's correct): wideband IQ sample rates and FFT processing are demanding relative to an MCU's compute, even one with ESP32-P4's AI accelerator. On-device spectrum analysis is not what this module attempts. The realistic architecture — and the one implemented here — is: pull raw IQ samples off the dongle via USB host, and forward them upstream for the backend to FFT/analyze (the same job the browser already does client-side today via frontend/src/lib/fft.ts + frontend/src/lib/sdr.ts's SpectrumAnomalyDetector). Even that "just pass the bytes through" architecture needs real USB throughput numbers to know if it's viable — see "What's unverified" below.

Primary reference

frontend/src/lib/sdr.ts — this repo's existing browser-based (WebUSB) RTL2832U + R820T driver. It's real, already-researched protocol detail against the public librtlsdr register documentation (vendor commands, I2C-repeater tuner access, the demod/tuner init sequence), itself marked HARDWARE PASS REQUIRED since it's never been run against a real dongle either. This firmware module is a direct port of that file's control- transfer sequence from WebUSB JS calls to ESP-IDF USB Host Library C calls — line-by-line correspondences are called out in code comments (e.g. rtlsdr_run_init_sequence() mirrors open() in sdr.ts almost register-for-register). It intentionally does not re-derive any register math from scratch; wherever sdr.ts says "simplified" or "HARDWARE PASS REQUIRED" (e.g. the R820T PLL frequency math, the demod resample-ratio math), this module carries the exact same simplification forward with the exact same caveat, rather than inventing new unverified math on top of already-unverified math.

What's implemented (structurally — see caveats below)

1. USB Host Library lifecycle (rtlsdr_exp_start() / rtlsdr_usb_lib_daemon_task() / rtlsdr_exp_client_task()): usb_host_install(), usb_host_client_register() with an async event callback, and the two-task pump pattern the USB Host Library's async model requires (one task for usb_host_lib_handle_events(), one for usb_host_client_handle_events() — the latter also being how this module's own control- and bulk-transfer completion callbacks get dispatched, since the Library calls them synchronously from whichever task is pumping events, not from a hidden thread or ISR).
2. RTL2832U/Terratec device enumeration and vendor-ID matching (rtlsdr_try_bring_up(), rtlsdr_vendor_id_matches()): on a USB_HOST_CLIENT_EVENT_NEW_DEV event, opens the device, reads its device descriptor, and matches idVendor against 0x0BDA (RTL2832U) / 0x0CCD (Terratec-rebadged) — ported directly from sdr.ts's requestDevice() filter list (RTL2832U_VENDOR, TERRATEC_VENDOR). Faithfully carries over that file's specific choice to filter by vendor ID only, not product ID (its comment: "many dongles report product ids outside the handful we know, so filtering by productId hides them from the picker") — the known product-id list (RTLSDR_EXP_KNOWN_PRODUCT_IDS) is kept as an informational log line only, never a hard filter, exactly mirroring how RTL2832U_PRODUCTS is exported-but-unused-as-a-filter in sdr.ts.
3. RTL2832U init vendor-command sequence over USB control transfers (rtlsdr_run_init_sequence(), rtlsdr_demod_write(), rtlsdr_reg_write(), rtlsdr_i2c_write(), rtlsdr_exp_set_frequency(), rtlsdr_exp_set_sample_rate()): the same demod soft-reset → demod_ctl/ suspend-off block → standby-off → AGC-mode → R820T tuner power-up (through the I2C repeater) → sample-rate program → initial tune → streaming-endpoint reset → test-mode-off sequence as sdr.ts's open(), with the same register addresses/values and the same wValue/wIndex encoding ((block<<8)|0x10 / (page<<8)|address), translated from USBDevice.controlTransferOut() to usb_host_transfer_submit_control() with a manually-built usb_setup_packet_t.
4. A basic bulk-transfer read loop structure for pulling IQ sample data off the device (rtlsdr_start_bulk_streaming(), rtlsdr_bulk_xfer_cb()): unlike sdr.ts (which does one-shot await dev.transferIn(...) calls from inside its own async sweep() loop), the USB Host Library is callback-driven, so continuous streaming here is a small pipeline — N transfers (bulk_read_queue_ depth, default 4) of a fixed chunk size (bulk_read_chunk_bytes, default 16384B, enforced as a multiple of 512 the same way sdr.ts's readSamples() comment requires) are kept perpetually in flight; each completion callback copies the received bytes into a heap block, hands it to a FreeRTOS queue for the forward task, and immediately resubmits itself to keep the pipe full. This is the part most likely to need real-hardware tuning — see below.
5. A stub/structure for forwarding raw IQ data upstream (rtlsdr_exp_forward_iq_block(), rtlsdr_forward_task()) — see the architecture decision writeup immediately below.

IQ-forwarding architecture decision

The spec explicitly leaves this as a product-judgment call ("your call on whether this warrants a separate endpoint/stream vs. reusing the sensor telemetry shape with a binary/base64 payload"). Decision made here: a separate binary stream/endpoint, not a reuse of the JSON telemetry shape. Reasoning:

• Raw throughput is the wrong order of magnitude for the telemetry contract. Even a modest 2.048 Msps capture at 8 bits/sample/channel (RTL2832U's native ADC format) is interleaved I/Q bytes at roughly 4.1 MB/s. The design spec's POST /api/device/telemetry contract caps the readings array at ~64 entries, caps the request body at ~16KB, and rate-limits ingestion to roughly 1 request/second sustained per device — sized for a handful of scalar sensor readings (temperature, humidity, presence booleans), not a continuous multi-megabyte/second binary stream. Forcing IQ data through that shape would mean either violating those caps (defeating their whole purpose — bounding what a misbehaving/malicious device can push at the backend) or chopping IQ into thousands of tiny requests per second, which is worse for both sides than one continuous stream.
• Base64-in-JSON adds ~33% size overhead on top of a payload that's already too large for the telemetry shape, for no benefit — there's no reason to pay text-encoding tax on a payload nothing needs to eyeball as text.
• It's a fundamentally different kind of data with different backend handling needs. Telemetry readings feed the anomaly-detection baseline/threshold pipeline directly and cheaply (a few floats per sensor). IQ data needs FFT processing before it's useful for anything — an entirely different backend code path (closer to how the browser's own powerSpectrumDb() + SpectrumAnomalyDetector work today, server-side instead of client-side). Conflating the two request shapes would couple two things that should scale, rate-limit, and fail independently.

Given that, this module's stub (rtlsdr_exp_forward_iq_block()) targets a separate, currently-hypothetical endpoint (iq_upload_url in rtlsdr_exp_config_t, suggested path /api/device/iq-stream in code comments) carrying a small fixed binary header (magic, sequence number, center frequency, sample rate, payload length — see rtlsdr_iq_chunk_header_t) followed by the raw IQ bytes, POSTed as application/octet-stream with the same Authorization: Bearer <device token> auth as the regular telemetry loop. This endpoint does not exist anywhere in this repo. Building it is explicitly out of scope for this workstream (it's backend work, not firmware, and the spec doesn't assign a backend workstream to receive IQ data at all — only to receive scalar telemetry). The stub is inert by default (rtlsdr_exp_forward_ iq_block() returns ESP_OK immediately unless iq_upload_url is configured) specifically so this module can be compiled/enabled for its USB-host/bring-up behavior without requiring a backend that doesn't exist.

A real product decision here — genuinely open, not resolved by this workstream — is whether a POST-per-chunk model is even right versus a persistent WebSocket stream (the spec's /ws/device-feed design already establishes a WS pub/sub pattern on the backend for telemetry; a /ws/device-iq sibling might fit that architecture better than repeated HTTP POSTs, especially if backpressure/flow-control matters, which for a continuous stream it very much does). That's flagged here rather than silently decided, because it depends on backend design judgment as much as firmware judgment.

What's unverified — an honest, specific list for real hardware bring-up

Nothing below has run against real hardware. In rough order of "most likely to break first":

1. USB Host Library API surface. Function names, struct field names, and callback signatures (usb_host_client_config_t's .async. client_event_callback shape in particular — ESP-IDF has changed this API's shape across versions) are written from documented/remembered API shape, not checked against a real ESP-IDF checkout (none available in this environment). First thing a real bring-up needs: does this even compile against the ESP-IDF version Workstream I's project targets?
2. RTL2832U enumeration over a real ESP32-P4 USB-OTG host port — does usb_host_device_open() / usb_host_get_device_descriptor() actually see the dongle at all on this specific chip's USB-OTG controller (power delivery to the dongle over USB-host mode is itself a hardware question — does the ESP32-P4 dev board supply VBUS in host mode, does the dongle draw more current than it can supply).
3. The init vendor-command sequence itself — carried over unchanged from sdr.ts, which is itself unverified. Two layers of "reasoned, not tested." A logic analyzer / USB protocol analyzer trace against a real dongle (or cross-checking against real librtlsdr -T verbose output) is needed to confirm register values, not just transfer plumbing.
4. R820T PLL frequency math and demod resample-ratio math — both are the same simplified integer-N approximation sdr.ts uses (its own comment: "real librtlsdr computes the exact sdm/vco from a 28.8MHz crystal reference. Simplified... Marked for hardware."). Likely wrong or imprecise until replaced with the real librtlsdr formula and checked against an actual received signal.
5. Bulk transfer chunk size, pipeline depth, and timeout=0 choice (RTLSDR_EXP_BULK_CHUNK_BYTES/RTLSDR_EXP_BULK_QUEUE_DEPTH Kconfig, defaults 16384B / depth 4) — these are guesses. Real ESP32-P4 USB Host Library heap/DMA limits, achievable sustained throughput at 2.048 Msps (~4.1 MB/s), and whether timeout_ms = 0 (no timeout, i.e. "block until data or disconnect") is even the right transfer mode for this endpoint all need real measurement.
6. Drop-on-full backpressure policy (iq_blocks_dropped stat) — is silently dropping IQ blocks when the forward task falls behind acceptable, or does it need real flow control (e.g. throttling the bulk read rate itself)? Depends on (5) and on real WiFi uplink bandwidth from a real device on a real seeker's home network.
7. The proposed IQ-forwarding wire format and endpoint — entirely hypothetical (see architecture section above); no backend exists to validate the framing against, and the POST-vs-WebSocket question above is unresolved.
8. Concurrent USB Host Library ownership with the rest of the firmware project. rtlsdr_exp_start()/rtlsdr_exp_stop() call usb_host_ install()/usb_host_uninstall() directly, assuming this module is the only USB Host client in the project. If Workstream I's skeleton (or anything else) also needs USB host for something, this needs to change to a shared-ownership model (install once, both modules register as clients) — impossible to resolve without seeing that code, flagged here for whoever does the merge.
9. Memory footprint. Multiple in-flight 16KB bulk transfer buffers plus a forward queue plus esp_http_client buffers, alongside whatever Workstream I's WiFi/HTTP/BME280/presence stack already needs, on a single ESP32-P4's RAM — not sized or measured against a real linker map.

Build / integration notes

This component is off by default (RTLSDR_EXP_ENABLE Kconfig option, default n) so it cannot affect Workstream I's core build unless explicitly turned on via idf.py menuconfig → "RTL-SDR Experimental Module." To include it in a real project once Workstream I's skeleton exists:

1. Add this directory's components/ to the consuming project's EXTRA_COMPONENT_DIRS in the top-level CMakeLists.txt (or copy components/rtlsdr_experimental/ into that project's own components/).
2. From wherever app_main() sets up its other sensor drivers, e.g.:

   #include "rtlsdr_experimental.h"
   
   rtlsdr_exp_config_t sdr_cfg;
   rtlsdr_exp_config_default(&sdr_cfg);
   sdr_cfg.iq_upload_url = NULL; /* leave unset until a real backend
                                     endpoint exists — see README */
   sdr_cfg.device_bearer_token = DEVICE_BEARER_TOKEN; /* from
                                     main/device_config.h, same token
                                     used for the telemetry POST loop */
   rtlsdr_exp_handle_t sdr_handle;
   if (rtlsdr_exp_init(&sdr_cfg, &sdr_handle) == ESP_OK) {
       rtlsdr_exp_start(sdr_handle); /* non-blocking; watches for a dongle */
   }
   

3. idf.py build — not run in this environment (no ESP-IDF toolchain available); this module has only been reasoned about, not compiled. Treat "compiles" as an open question for the next person with a real toolchain, not a claim made here.

Verified in this environment: none of it, against hardware or a real compiler. What has been done: careful structural translation of a real, already-partially-researched protocol (sdr.ts) to the documented shape of a real, chip-specific API (ESP32-P4's USB Host Library), with every simplification and open question called out rather than hidden.