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Ben Meadors b565a07a83 Remove proprietary Bosch BSEC blob; open in-tree IAQ estimator for BME680 (#11381 )

* Remove proprietary Bosch BSEC blob; open in-tree IAQ estimator for BME680

BSEC2 cost ~37-39 KB flash and ~4-5 KB static RAM on ~190 of ~240 build
targets, linked whether or not a BME680 was attached, and was a no-source
proprietary archive inside GPLv3 release binaries. The firmware consumed
exactly one BSEC-exclusive output: the IAQ value.

- New BME680IaqEstimator: clean-room log-domain baseline tracker
  (humidity-compensated gas resistance vs a rise-fast/decay-slow ceiling,
  0-500 scale matching the existing UI bands), pure math, unit-tested on
  native (test_bme680_iaq, 15 tests incl. a deep-sleep reboot simulation).
  Warm-up/burn-in progress persists to /prefs/bme680.dat via SafeFile so
  one-sample-per-wake SENSOR nodes converge across reboots; stale
  /prefs/bsec.dat is removed once.
- BME680Sensor: single-path rewrite on Adafruit_BME680 with async
  once-per-minute sampling (~20x lower heater duty than BSEC LP mode),
  a hard 2-minute publish-freshness bound (a dead sensor stops reporting
  instead of freezing its last reading on the wire), and suppression of
  bogus gas_resistance=0 points from heater-unstable cycles.
- platformio.ini: environmental_extra_common/_extra/_no_bsec collapsed
  into one section; Bosch BSEC2 + BME68x deps deleted; per-variant BSEC
  link-path hacks and the TEMPORARY promicro lib_ignore removed.
  nrf52_promicro_diy_tcxo regains BME680 support at 36 KB clear of the
  warm-store cap; rak4631 lands at 75 KB clear.
- EnvironmentTelemetry: iaq rendering gates on has_iaq (a genuine IAQ of
  0 now displays); stale BSEC comments rewritten.
- rak4631 size budgets tightened (113000->108000 RAM, 786000->746000
  flash) to lock in the reclaimed headroom.
- bin/bme680_iaq_replay.cpp: host-side replay harness for tuning the
  estimator against captured BSEC traces (mean abs error + band
  agreement), no reflashing needed.

Measured (develop -> this branch): rak4631 -38.8 KB flash / -4.9 KB RAM;
heltec-v3 -36.4 KB / -4.0 KB; tlora-v2-1-1_6 +1.3 KB (its IAQ
approximation had been dead code since #9663 due to an inverted isfinite
check and now actually runs).

Note: gas_resistance stays kOhm on the wire for fleet compatibility; the
proto comment claiming MOhm gets a separate meshtastic/protobufs docs PR.

* Address CodeRabbit review feedback

- Use Throttle::isWithinTimespanMs for all elapsed-time predicates in
  BME680Sensor per coding guidelines (deadline math for the async reading
  completion stays raw, as it targets an absolute timestamp)
- Make the state file name members static constexpr
- Replay tool: cast uint16_t before %u (default argument promotion), report
  malformed input lines instead of silently skipping, and fail non-zero on
  stream read errors

* Address CodeRabbit nitpicks

- Replace the local clampf helper with std::clamp (meshUtils.h's clamp drags
  in Arduino.h, which would break the estimator's standalone host build that
  the replay harness depends on)
- Trim the replay tool's file header to a two-line summary; the full build,
  capture, and tuning workflow moves to docs/bme680_iaq_replay.md

2026-08-13 13:21:16 -04:00

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BME680 IAQ replay harness

bin/bme680_iaq_replay.cpp replays a captured sensor trace through the in-tree BME680IaqEstimator on a dev machine, for tuning the estimator's constants against recorded Bosch BSEC output. The estimator is pure math with no platform dependencies, so a trace replays in milliseconds - edit the constants in src/modules/Telemetry/Sensor/BME680IaqEstimator.h, recompile, rerun.

Build

From the repo root:

c++ -std=c++17 -O2 -I src -o /tmp/iaq_replay \
    bin/bme680_iaq_replay.cpp src/modules/Telemetry/Sensor/BME680IaqEstimator.cpp

Input

CSV on stdin or as a file argument, one sample per line:

gas_ohms,relative_humidity[,bsec_iaq]

Lines starting with # are ignored; a single non-numeric header row is tolerated; any other malformed line is reported on stderr and skipped.

Capturing a trace

On a firmware build that still links BSEC (any release tag before the BSEC removal), add one log line to BME680Sensor::getMetrics in the BSEC branch:

LOG_INFO("IAQCSV,%.0f,%.2f,%.0f", bme680.getData(BSEC_OUTPUT_RAW_GAS).signal,
         bme680.getData(BSEC_OUTPUT_SENSOR_HEAT_COMPENSATED_HUMIDITY).signal,
         bme680.getData(BSEC_OUTPUT_IAQ).signal);

then extract the columns from the serial log:

grep -o 'IAQCSV,.*' serial.log | cut -d, -f2- > trace.csv

BSEC's RAW_GAS and heat-compensated humidity are exactly the estimator's inputs, so one physical sensor feeds both algorithms identically.

Output

Per-sample CSV n,gas_ohms,rh,est_iaq,bsec_iaq on stdout (empty est_iaq during the estimator's warm-up/burn-in window), plus a stderr summary with the mean absolute error and UI-band agreement against the bsec_iaq column, using the same 0-500 band thresholds the device screen applies.

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