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Merged
nedseb merged 2 commits into from
Mar 29, 2026
Merged

feat(bme280): Add measurement modes and sensor configuration #313

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8b142fc
feat(bme280): Add measurement modes and sensor configuration.
nedseb Mar 29, 2026
f63099a
fix(bme280): Rewrite ctrl_meas after ctrl_hum to latch humidity config.
nedseb Mar 29, 2026
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71 changes: 71 additions & 0 deletions lib/bme280/bme280/device.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,22 +7,26 @@
CALIB_H_SIZE,
CALIB_TP_SIZE,
DATA_BLOCK_SIZE,
FILTER_SHIFT,
MODE_FORCED,
MODE_MASK,
MODE_NORMAL,
MODE_SLEEP,
OSRS_P_SHIFT,
OSRS_T_SHIFT,
OSRS_X1,
REG_CALIB_HUM,
REG_CALIB_TEMP_PRESS,
REG_CHIP_ID,
REG_CONFIG,
REG_CTRL_HUM,
REG_CTRL_MEAS,
REG_DATA_START,
REG_SOFT_RESET,
REG_STATUS,
RESET_DELAY_MS,
SOFT_RESET_CMD,
STANDBY_SHIFT,
STATUS_IM_UPDATE,
STATUS_MEASURING,
)
Expand Down Expand Up @@ -139,6 +143,73 @@ def reset(self):
self._read_calibration()
self._configure_default()

# --------------------------------------------------
# Power and mode control
# --------------------------------------------------

def power_off(self):
"""Enter sleep mode. Stops all measurements."""
ctrl = self._read_reg(REG_CTRL_MEAS)
self._write_reg(REG_CTRL_MEAS, ctrl & ~MODE_MASK)

def power_on(self):
"""Enter normal mode. Continuous measurements at configured standby rate."""
ctrl = self._read_reg(REG_CTRL_MEAS)
self._write_reg(REG_CTRL_MEAS, (ctrl & ~MODE_MASK) | MODE_NORMAL)

def set_continuous(self, standby=None):
"""Start continuous measurements in normal mode.

Args:
standby: standby time constant (STANDBY_0_5_MS .. STANDBY_1000_MS).
If None, the current config register value is kept.
"""
if standby is not None:
self.set_standby(standby)
self.power_on()

# --------------------------------------------------
# Sensor configuration
# --------------------------------------------------

def set_oversampling(self, temperature=None, pressure=None, humidity=None):
"""Configure oversampling for one or more channels.

Args:
temperature: OSRS_SKIP .. OSRS_X16 (None = keep current).
pressure: OSRS_SKIP .. OSRS_X16 (None = keep current).
humidity: OSRS_SKIP .. OSRS_X16 (None = keep current).
"""
if humidity is not None:
self._write_reg(REG_CTRL_HUM, humidity)
if temperature is not None or pressure is not None:
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set_oversampling() writes REG_CTRL_HUM when humidity is provided, but if only humidity is changed (temperature/pressure are None) it never writes REG_CTRL_MEAS. On BME280, ctrl_hum updates take effect only after a subsequent write to ctrl_meas (your own _configure_default() comment notes this), so humidity-only changes won't actually apply. Fix by performing a (read-modify-)write to REG_CTRL_MEAS after writing REG_CTRL_HUM even when temperature/pressure are unchanged (preserving the existing mode/oversampling bits).

Suggested change
if humidity is not None:
self._write_reg(REG_CTRL_HUM, humidity)
if temperature is not None or pressure is not None:
update_ctrl_meas = False
if humidity is not None:
# On BME280, changes to ctrl_hum take effect only after
# a subsequent write to ctrl_meas.
self._write_reg(REG_CTRL_HUM, humidity)
update_ctrl_meas = True
if temperature is not None or pressure is not None or update_ctrl_meas:

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@nedseb nedseb Mar 29, 2026

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Already fixed in f63099a: set_oversampling() now always rewrites ctrl_meas after ctrl_hum, even when only humidity is changed. The comment in the code references datasheet section 5.4.3.

ctrl = self._read_reg(REG_CTRL_MEAS)
if temperature is not None:
ctrl = (ctrl & ~(0x07 << OSRS_T_SHIFT)) | (temperature << OSRS_T_SHIFT)
if pressure is not None:
ctrl = (ctrl & ~(0x07 << OSRS_P_SHIFT)) | (pressure << OSRS_P_SHIFT)
self._write_reg(REG_CTRL_MEAS, ctrl)

def set_iir_filter(self, coefficient):
"""Configure the IIR filter coefficient.

Args:
coefficient: FILTER_OFF .. FILTER_16.
"""
config = self._read_reg(REG_CONFIG)
config = (config & ~(0x07 << FILTER_SHIFT)) | (coefficient << FILTER_SHIFT)
self._write_reg(REG_CONFIG, config)

def set_standby(self, standby):
"""Configure the standby time for normal mode.

Args:
standby: STANDBY_0_5_MS .. STANDBY_1000_MS.
"""
config = self._read_reg(REG_CONFIG)
config = (config & ~(0x07 << STANDBY_SHIFT)) | (standby << STANDBY_SHIFT)
self._write_reg(REG_CONFIG, config)

# --------------------------------------------------
# Status
# --------------------------------------------------
Expand Down
132 changes: 132 additions & 0 deletions tests/scenarios/bme280.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -274,3 +274,135 @@ tests:
result = triggered and abs(t - 25.08) < 0.1
expect_true: true
mode: [mock]

# ----- Power and mode control -----

- name: "power_off sets sleep mode"
action: script
script: |
i2c.clear_write_log()
dev.power_off()
log = i2c.get_write_log()
wrote_sleep = any(reg == 0xF4 and (data[0] & 0x03) == 0x00 for reg, data in log)
result = wrote_sleep
expect_true: true
mode: [mock]

- name: "power_on sets normal mode"
action: script
script: |
i2c.clear_write_log()
dev.power_on()
log = i2c.get_write_log()
wrote_normal = any(reg == 0xF4 and (data[0] & 0x03) == 0x03 for reg, data in log)
result = wrote_normal
expect_true: true
mode: [mock]

- name: "power_off preserves oversampling bits"
action: script
script: |
from bme280.const import OSRS_X4, OSRS_T_SHIFT, OSRS_P_SHIFT
dev.set_oversampling(temperature=OSRS_X4, pressure=OSRS_X4)
i2c.clear_write_log()
dev.power_off()
log = i2c.get_write_log()
ctrl = [data[0] for reg, data in log if reg == 0xF4][-1]
osrs_t = (ctrl >> 5) & 0x07
osrs_p = (ctrl >> 2) & 0x07
result = osrs_t == OSRS_X4 and osrs_p == OSRS_X4 and (ctrl & 0x03) == 0x00
expect_true: true
mode: [mock]

- name: "set_continuous enters normal mode"
action: script
script: |
dev.power_off()
i2c.clear_write_log()
dev.set_continuous()
log = i2c.get_write_log()
wrote_normal = any(reg == 0xF4 and (data[0] & 0x03) == 0x03 for reg, data in log)
result = wrote_normal
expect_true: true
mode: [mock]

- name: "set_continuous with standby configures both"
action: script
script: |
from bme280.const import STANDBY_500_MS, STANDBY_SHIFT
i2c.clear_write_log()
dev.set_continuous(standby=STANDBY_500_MS)
log = i2c.get_write_log()
wrote_config = any(reg == 0xF5 for reg, data in log)
wrote_normal = any(reg == 0xF4 and (data[0] & 0x03) == 0x03 for reg, data in log)
result = wrote_config and wrote_normal
expect_true: true
mode: [mock]

# ----- Configuration -----

- name: "set_oversampling configures temperature and pressure"
action: script
script: |
from bme280.const import OSRS_X2, OSRS_X4, OSRS_T_SHIFT, OSRS_P_SHIFT
i2c.clear_write_log()
dev.set_oversampling(temperature=OSRS_X2, pressure=OSRS_X4)
log = i2c.get_write_log()
ctrl_writes = [data[0] for reg, data in log if reg == 0xF4]
ctrl = ctrl_writes[-1]
osrs_t = (ctrl >> OSRS_T_SHIFT) & 0x07
osrs_p = (ctrl >> OSRS_P_SHIFT) & 0x07
result = osrs_t == OSRS_X2 and osrs_p == OSRS_X4
expect_true: true
mode: [mock]

- name: "set_oversampling configures humidity"
action: script
script: |
from bme280.const import OSRS_X8
i2c.clear_write_log()
dev.set_oversampling(humidity=OSRS_X8)
log = i2c.get_write_log()
hum_writes = [data[0] for reg, data in log if reg == 0xF2]
result = len(hum_writes) == 1 and hum_writes[0] == OSRS_X8
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This test asserts set_oversampling(humidity=...) only writes REG_CTRL_HUM (0xF2). However, BME280 latches ctrl_hum changes only after a write to REG_CTRL_MEAS (0xF4), so the correct behavior should include a REG_CTRL_MEAS write as well. Update the expectation to also require (at least) one write to 0xF4 following the 0xF2 write.

Suggested change
hum_writes = [data[0] for reg, data in log if reg == 0xF2]
result = len(hum_writes) == 1 and hum_writes[0] == OSRS_X8
hum_index = None
for idx, (reg, data) in enumerate(log):
if reg == 0xF2 and data[0] == OSRS_X8:
hum_index = idx
break
if hum_index is None:
result = False
else:
wrote_ctrl_after = any(reg == 0xF4 for reg, data in log[hum_index + 1:])
result = wrote_ctrl_after

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Already fixed in f63099a: the test now verifies that both ctrl_hum (0xF2) and ctrl_meas (0xF4) are written, and that 0xF2 comes before 0xF4 in the write log.

expect_true: true
mode: [mock]

- name: "set_iir_filter writes config register"
action: script
script: |
from bme280.const import FILTER_16, FILTER_SHIFT
i2c.clear_write_log()
dev.set_iir_filter(FILTER_16)
log = i2c.get_write_log()
config_writes = [data[0] for reg, data in log if reg == 0xF5]
result = len(config_writes) == 1 and ((config_writes[0] >> FILTER_SHIFT) & 0x07) == FILTER_16
expect_true: true
mode: [mock]

- name: "set_standby writes config register"
action: script
script: |
from bme280.const import STANDBY_250_MS, STANDBY_SHIFT
i2c.clear_write_log()
dev.set_standby(STANDBY_250_MS)
log = i2c.get_write_log()
config_writes = [data[0] for reg, data in log if reg == 0xF5]
result = len(config_writes) == 1 and ((config_writes[0] >> STANDBY_SHIFT) & 0x07) == STANDBY_250_MS
expect_true: true
mode: [mock]

- name: "set_iir_filter preserves standby bits"
action: script
script: |
from bme280.const import STANDBY_500_MS, STANDBY_SHIFT, FILTER_4, FILTER_SHIFT
dev.set_standby(STANDBY_500_MS)
i2c.clear_write_log()
dev.set_iir_filter(FILTER_4)
log = i2c.get_write_log()
config = [data[0] for reg, data in log if reg == 0xF5][-1]
standby = (config >> STANDBY_SHIFT) & 0x07
filt = (config >> FILTER_SHIFT) & 0x07
result = standby == STANDBY_500_MS and filt == FILTER_4
expect_true: true
mode: [mock]
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