feat(bme280): Add altitude computation and sea-level pressure

[nedseb]

Closes #315

Summary

• sea_level_pressure attribute: initialized to 1013.25 hPa, user-adjustable for local conditions
• altitude() method: estimates altitude in meters using the ICAO barometric formula 44330 * (1 - (P/P0)^0.1903) — same formula used by robert-hh, Adafruit, and Pimoroni
• weather_station.py updated: uses sensor.altitude() instead of a local altitude_m() function; sea-level pressure configured via sensor.sea_level_pressure
• README updated: new Altitude section in API reference, comparison table updated (Altitude and Sea-level pressure now ✅)
• 4 new mock tests: default reference value, altitude with default/custom reference, altitude=0 when pressure matches reference

Test plan

• 52 mock tests pass (make test-bme280)
• Hardware validation

[Copilot]

Pull request overview

Adds altitude estimation to the BME280 driver via a configurable sea-level pressure reference, and updates docs/tests/examples accordingly.

Changes:

• Introduces sea_level_pressure (default 1013.25 hPa) and an altitude() method on the driver.
• Updates the weather_station.py example to use the driver’s altitude computation.
• Extends README and mock scenario tests to cover altitude and the new reference pressure.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
lib/bme280/bme280/device.py	Adds sea_level_pressure attribute and altitude() API.
lib/bme280/examples/weather_station.py	Switches example altitude calculation to sensor.altitude().
lib/bme280/README.md	Documents altitude usage and marks altitude/sea-level pressure supported in comparison table.
tests/scenarios/bme280.yaml	Adds mock tests for default sea-level pressure and altitude computations.

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[Copilot]

In this example loop, sensor.read() returns a pressure value that gets logged/printed, but sensor.altitude() immediately reads pressure again internally. That means pressure and alt may come from different measurements (and adds extra I2C traffic). Consider computing altitude from the already-read pressure (e.g., an altitude_from_pressure(pressure_hpa) helper or allowing altitude(pressure_hpa=...)), so all fields in the same row are consistent.

[nedseb]

Fixed in e920a67: weather_station.py now passes the already-read pressure to sensor.altitude(pressure_hpa=pressure), ensuring consistency between all fields in the same row.

[Copilot]

altitude() always calls pressure_hpa(), which forces an additional burst read (and may trigger a new measurement in sleep mode). This makes it hard to compute altitude from an already-fetched pressure value and can lead to inconsistent multi-field reads. Consider adding an optional pressure_hpa parameter (or a separate altitude_from_pressure() method) so callers can avoid redundant I2C reads and ensure consistent sampling.

Suggested change

	def altitude(self):
	"""Return estimated altitude in meters from current pressure.
	Uses the ICAO barometric formula with ``sea_level_pressure`` as
	reference (default 1013.25 hPa, adjustable).
	"""
	p = self.pressure_hpa()
	def altitude(self, pressure_hpa=None):
	"""Return estimated altitude in meters from current pressure.
	Uses the ICAO barometric formula with ``sea_level_pressure`` as
	reference (default 1013.25 hPa, adjustable).
	If ``pressure_hpa`` is provided, it is used directly; otherwise a new
	pressure reading is obtained via :meth:`pressure_hpa`.
	"""
	p = self.pressure_hpa() if pressure_hpa is None else pressure_hpa

[nedseb]

Fixed in e920a67: altitude() now accepts an optional pressure_hpa parameter. When provided, it skips the I2C read and uses the given value directly.

[Copilot]

sea_level_pressure is user-adjustable and used as a divisor in altitude(). If it’s set to 0 or a negative value, altitude() will raise (or return nonsensical results). Add validation (e.g., require a positive float) and raise a clear ValueError when the value is invalid.

Suggested change

	p = self.pressure_hpa()
	return 44330.0 * (1.0 - (p / self.sea_level_pressure) ** 0.1903)
	slp = getattr(self, "sea_level_pressure", None)
	try:
	if slp is None or slp <= 0:
	raise ValueError(
	"sea_level_pressure must be a positive float, got: {!r}".format(slp)
	)
	except TypeError:
	raise ValueError(
	"sea_level_pressure must be a positive float, got: {!r}".format(slp)
	)
	p = self.pressure_hpa()
	return 44330.0 * (1.0 - (p / slp) ** 0.1903)

[nedseb]

Not addressed: this is an internal attribute, not user input from an external boundary. The project convention is to only validate at system boundaries (user input, external APIs), not internal driver state. Adding defensive validation here would be inconsistent with the rest of the codebase.

[Copilot]

The new public attribute name sea_level_pressure doesn’t encode its units, while the rest of the public API does (e.g., pressure_hpa(), read() returns pressure_hpa). To avoid user confusion (Pa vs hPa), consider renaming to sea_level_pressure_hpa or providing a documented property with unit in its name.

[nedseb]

Fixed in e920a67: renamed to sea_level_pressure_hpa for consistency with the rest of the API (pressure_hpa(), etc.).

[semantic-release-updater]

🎉 This PR is included in version 0.8.0 🎉

The release is available on:

• v0.8.0
• GitHub release

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