PiPod

PiPod — Raspberry Pi 5 SDR sensor pod (v0.2)

Pi-side host for the v0.2 hardware pivot. Each pod runs an SDR + a two-stage detector and forwards classified DetectPacket payloads over UART to an ESP32-C6 companion that owns the SX1262 and runs the existing RadioLib / AES-128-EAX firmware unchanged.

Rationale, SDR selection, and milestones: ../docs/V02_PIVOT.md. Issue/change backlog: ../V02_GAP_ANALYSIS.md.

Status: scaffold. Files here establish structure and contracts. DSP bodies are skeletons with TODOs — they have not been run against real SDR hardware.

Option B — the Pi does NOT have a LoRa HAT

The SX1262 is owned by the ESP32-C6 companion, not a Pi HAT. Keeping crypto on the bare-metal ESP32-C6 holds the trusted computing base to ~30 KB; a compromised Pi cannot exfiltrate session keys because they never reach it. The Pi↔ESP32-C6 link is one-way (Pi → ESP32-C6) carrying detection metadata only — never key material. See ../SECURITY.md (Pi pod threat model — gap A4, pending) and the HAT survey in ../docs/V02_PIVOT.md §2 (reference only; we reject the Pi-side-RadioLib "Option A").

Layout

Path	Purpose	Gap
detector/	Always-on C energy detector (librtlsdr/libhackrf + FFTW, /dev/shm ring buffer)	E1
classifier/	Python signature classifiers, invoked only on energy-threshold trigger	E2
uart_bridge/	Pi→ESP32-C6 framing — uart_proto.{md,h}	E3
docs/pps.md	GPS PPS distribution to both Pi (chrony) and ESP32-C6	C3
systemd/	Service unit + chrony example	A1
REFERENCES.md	Upstream projects we build on	E4
.github/workflows/build.yml	arm64 C build + Python lint/test	F1

Base image

Use DragonOS Pi64 (Beta42 or newer) — it ships RTL-SDR/HackRF/bladeRF drivers, GNU Radio, SDR++, and rtl-433 preconfigured for Pi 5. See REFERENCES.md.

Pi 5 GPIO / SPI gotchas (from pivot doc §2)

• Pi 5 uses the RP1 I/O chip: GPIO character device is /dev/gpiochip4 (not 0).
• Use lgpio (chardev API), not the deprecated wiringPi/pigpio.
• GPS UART is /dev/ttyS0 on Pi 5 (was /dev/ttyAMA0 on Pi ≤4).
• PPS is GPIO-only on Pi 5: dtoverlay=pps-gpio,gpiopin=18.

Power & thermal

~4.2 W idle, ~7–9 W active. Active cooling is mandatory (throttles at ~86.7 °C without it). Battery life and solar options: ../ModuleDesign/BOM.md.

Per-pod SDR (see BOM)

Pod	Band	SDR
A	5.8 GHz FPV video	HackRF One
B	2.4 GHz FPV control / OcuSync / ELRS 2.4	HackRF One
C	GNSS L1 jam	RTL-SDR Blog V3 + active L1 patch
D	868 MHz EU ISM	RTL-SDR Blog V3 + 868 BPF
E	Tactical VHF 30–88 MHz	RTL-SDR Blog V3