MeshCore

Nick Dunklee 59cee5c8a0 feat: Integrate BME680 Bosch BSEC support for RAK4631

This is a consolidation of my changes for BME680 on RAK4631 nodes.
I will close my other PRs related to this and link back to this one.

*Background on change:*

This change replaces the Adafruit BME680 driver on RAK4631 with the
Bosch BSEC library. Other boards continue to use the existing
Adafruit path via ENV_INCLUDE_BME680.

This makes the IAQ portion of the sensor functional, and more accurate.
It also contains the math and/or CayenneLPP fixes from my other PRs.
The Bosch code also appears to handle calibrating sensor aging as well,
whereas the Adafruit code is just looking at blind values that can drift
with time. Pretty cool to see this shooting out useful data!

RAK4631 platform.io is set to override to ENV_INCLUDE_BME680_BSEC while
leaving the Adafruit code for other node types. (If this becomes applicable
for other node types in future, awesome! I just don't have hardware
to test against.)

Using the BSEC library introduces IAQ sensor calibration, and saves
the calibration state periodically so it does not have to calibrate
again later.

At startup the IAQ sensor takes 30 minutes to heat and to hit a baseline,
then starts calibrating. Once calibrated, it will save those settings
and will only write settings again if calibration falls back and restores
back to state 3.

This fix also has the gas resistance math fix that was in
[pull 2146](https://github.com/meshcore-dev/MeshCore/pull/2146) so
the adafruit path also can at least show accurate values instead
of looping negative.

Also includes the fix from [pull 2149](https://github.com/meshcore-dev/MeshCore/pull/2149) so the pressure output isn't truncated to 1hPa steps.

*Fixes/Changes:*
- Add bsec_config_iaq[] with the 3.3V/3s-LP/28d calibration profile
- BSEC init applies setConfig() for voltage-correct heater targeting
- IAQ, heat-compensated temperature/humidity, pressure, and altitude
reported over CayenneLPP
- IAQ accuracy reported as analog input over CayenneLPP (0,1,2,3)
- Calibration state persisted to /bsec_state.bin on nRF52 internal
flash; written only when iaqAccuracy improves to >= 2, should
keep write frequency well within flash endurance over device lifetime
- Fix non-BSEC query_bme680: float pressure division, addGenericSensor
for gas resistance (was addAnalogInput, overflows at > 327 Ohm)
- loop() correctly gated for both GPS and BSEC-only builds
- Add fix_bsec_lib.py extra_script to resolve nRF52840 hard-float ABI
mismatch in Bosch's PlatformIO packaging, silly Bosch

One general note outside of this code change: I noticed while BME680
_functions_ in companion nodes, since companion nodes run Bluetooth,
BLE preempts the CPU, and can do so mid-I2C-transaction.

This can cause the BME680 to see an anomaly and drop calibration and
start a recalibrate. This is behavior that will exist (and has existed)
regardless of using the Adafruit or Bosch paths.

This particular companion behavior does not seem to occur in sensor
or repeater nodes since their BLE is off. Probably affects other
I2C devices as well.

*Tests:*

- RAK19003
- RAK19007
- RAK19001
- repeater, sensor, companion

2026-05-27 15:33:48 -06:00