After external IPEX antennas were added to the ESP32-S3 mesh nodes, a confirmed-empty
room read "present" indefinitely. Two root-cause bugs:
1. motion_score saturation. `variance_motion` and `mbp_motion` used fixed divisors
(/10, /25) calibrated for the antenna-less regime. Antennas raised amplitudes ~5x
and these amplitude^2 energies ~30x, pinning both terms at the 1.0 clamp — so
raw_motion could not fall near the presence floor and the adaptive baseline
subtraction in smooth_and_classify was defeated. Normalize both by signal power
(mean_amp^2) — the same dimensionless sqrt-of-power-ratio form already used by
temporal_motion_score — making motion_score amplitude-scale-invariant. This fixes
the single shared extract_features_from_frame used by BOTH the aggregate and the
per-node paths, so room-level presence benefits too. (csi.rs carries the identical
change in its dead mirror copy to keep the two in sync.)
2. parse_esp32_frame header offsets were 2 bytes early vs the firmware layout
(csi_collector.c csi_serialize_frame: seq @ [12..16), rssi @ [16], noise_floor @
[17]). rssi was decoded from sequence-counter byte 2 — which stays 0 for the first
65,536 frames — yielding an impossible rssi=0 dBm that zeroed the RSSI fusion
weights and the SNR-based signal_quality. The I/Q payload at byte 20 was already
correct (CSI_HEADER_SIZE == 20), so amplitude-derived features were unaffected.
Adds regression tests asserting motion_score is amplitude-scale-invariant and that a
quiet high-amplitude signal does not saturate. Full binary suite green (103 tests).
Validated live on the 2-node mesh: RSSI now reports real values (-28..-74 dBm, was 0)
and an empty room now produces genuine low-motion frames. A residual over-read remains
(real multi-subcarrier CSI reads elevated even when empty) — that intrinsic empty-vs-
still ambiguity needs a learned reference (adaptive classifier retrain), tracked separately.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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