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feat: add IIR filter configuration via BME280_IIR_FILTER env var #14

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Merged
guillaumedelre merged 1 commit into from
May 14, 2026
+8 −0
Merged

feat: add IIR filter configuration via BME280_IIR_FILTER env var #14

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2 changes: 2 additions & 0 deletions .env.example
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
# I2C configuration
BME280_I2C_BUS=1
BME280_I2C_ADDRESS=0x77
# IIR filter coefficient: 0=off 1=2x 2=4x 3=8x 4=16x (recommended: 2 for indoor use)
BME280_IIR_FILTER=0

# MQTT broker
MQTT_BROKER_HOST=192.168.1.x
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2 changes: 2 additions & 0 deletions README.md
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Expand Up @@ -111,6 +111,7 @@ All settings are driven by environment variables. Copy `.env.example` to `.env`
|----------|---------|-------------|
| `BME280_I2C_BUS` | `1` | I²C bus number (`1` for Pi Rev 2+, `0` for Rev 1) |
| `BME280_I2C_ADDRESS` | `0x77` | Sensor I²C address (`0x77` or `0x76` depending on SDO pin) |
| `BME280_IIR_FILTER` | `0` | IIR filter coefficient: `0`=off, `1`=2×, `2`=4×, `3`=8×, `4`=16× (recommended: `2` for indoor use) |
| `MQTT_BROKER_HOST` | `localhost` | IP or hostname of your MQTT broker |
| `MQTT_USERNAME` | _(empty)_ | MQTT username (leave empty for anonymous) |
| `MQTT_PASSWORD` | _(empty)_ | MQTT password |
Expand All @@ -123,6 +124,7 @@ All settings are driven by environment variables. Copy `.env.example` to `.env`
```ini
BME280_I2C_BUS=1
BME280_I2C_ADDRESS=0x77
BME280_IIR_FILTER=0

MQTT_BROKER_HOST=192.168.1.10
MQTT_USERNAME=homeassistant
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4 changes: 4 additions & 0 deletions bme280.py
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Expand Up @@ -7,6 +7,9 @@
I2C_BUS = int(os.environ.get('BME280_I2C_BUS', '1'))
DEVICE_ADDRESS = int(os.environ.get('BME280_I2C_ADDRESS', '0x77'), 16)

# IIR filter coefficient: 0=off, 1=2, 2=4, 3=8, 4=16 (see datasheet table 28)
IIR_FILTER = int(os.environ.get('BME280_IIR_FILTER', '0'))


def _get_short(data: list[int], index: int) -> int:
return c_short((data[index + 1] << 8) + data[index]).value
Expand Down Expand Up @@ -54,6 +57,7 @@ def read_all(addr: int = DEVICE_ADDRESS) -> tuple[float, float, float]:
time.sleep(0.002) # 2ms startup delay (datasheet section 4.2)
_wait_nvm_copy(bus, addr)

bus.write_byte_data(addr, 0xF5, IIR_FILTER << 2) # config: filter bits [4:2]
bus.write_byte_data(addr, 0xF2, OVERSAMPLE_HUM)
bus.write_byte_data(addr, 0xF4, OVERSAMPLE_TEMP << 5 | OVERSAMPLE_PRES << 2 | MODE)

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