Environmental Hardware I/O

The hardware_io.environmental package provides hardware interfaces and concrete implementations for environmental sensors such as barometric pressure sensors.

The goal of this package is to expose raw environmental measurements from physical devices while remaining independent of any application, user interface, or higher-level processing. Environmental calculations such as weather prediction, altitude estimation, sensor fusion, or trend analysis belong in higher-level controllers.

Design Goals

• Hardware abstraction through common interfaces
• Application-independent design
• Consistent units across all implementations
• Support multiple sensor vendors and communication methods
• Simple, primitive getter-based API
• Suitable for embedded and Raspberry Pi platforms

Current Sensors

Future implementations may include:

• BMP280
• BME280
• BME680
• SHT31
• Other environmental sensors

Directory Layout

environmental/
├── __init__.py
├── barometric_sensor_if.py
├── bmp3xx.py
├── bmp388.py
├── bmp390.py
├── component_test/
└── README.md

Bmp3xx contains the shared BMP388/BMP390 implementation. Bmp388 and Bmp390 remain available as compatibility names for existing configuration and imports.

Responsibilities

This module is responsible for:

• Initializing environmental sensors
• Reading pressure measurements
• Reading temperature measurements
• Managing hardware resources
• Reporting sensor status

This module is not responsible for:

• Altitude calculations
• Weather forecasting
• Pressure trend analysis
• Sensor fusion
• Navigation
• Data logging
• User interface

Those responsibilities belong to higher-level controllers.

Units

The hardware interfaces expose measurements using SI units.

Returning consistent units allows higher-level software to perform calculations without needing device-specific conversions.

Example

from hardware_io.environmental import Bmp388

sensor = Bmp388()

try:
    sensor.start()

    pressure = sensor.get_pressure_pa()
    temperature = sensor.get_temperature_c()

    print(f"Pressure: {pressure:.1f} Pa")
    print(f"Temperature: {temperature:.1f} °C")

finally:
    sensor.stop()

Raspberry Pi Dependencies

The BMP388 and BMP390 implementations use Adafruit’s CircuitPython driver.

python3 -m pip install \
    adafruit-blinka \
    adafruit-circuitpython-bmp3xx

The project installer can install the same system and Python dependencies. Choose exactly one driver:

scripts/installers/host_setup.sh --feature bmp388

or:

scripts/installers/host_setup.sh --feature bmp390

The interactive host_setup_tui.sh installer provides the same choice under Environmental sensors.

Hardware Setup

Connect the BMP388 or BMP390 breakout to the Raspberry Pi I²C bus:

Check the voltage requirements of the specific breakout board before wiring it. Enable I²C through sudo raspi-config, then verify that the sensor is visible:

i2cdetect -y 1

The default address is 0x77. A board configured with SDO low commonly appears at 0x76.

Component Testing

Run the live BMP388 hardware test from the project root:

python3 -m hardware_io.environmental.component_test.barometric_cli

The CLI reports pressure in pascals and temperature in degrees Celsius once per second. Press Ctrl+C to stop it.

Read one sample and exit:

python3 -m hardware_io.environmental.component_test.barometric_cli --once

Display pressure in inches of mercury and temperature in Fahrenheit:

python3 -m hardware_io.environmental.component_test.barometric_cli --imperial

Use address 0x76 or change the sampling interval:

python3 -m hardware_io.environmental.component_test.barometric_cli \
    --address 0x76 \
    --interval 0.5

The same component test can exercise a BMP390:

python3 -m hardware_io.environmental.component_test.barometric_cli \
    --sensor bmp390

Run the CLI with --help to see all options.

Troubleshooting

• If i2cdetect does not show 76 or 77, check power, ground, SDA, SCL, and whether I²C is enabled.
• If initialization fails at 0x77, scan the bus and pass --address 0x76 when that is the reported address.
• If Python reports a missing board or adafruit_bmp3xx module, install the dependencies above in the same Python environment used to run the test.
• If access to /dev/i2c-* is denied, check the device permissions and the current user’s group membership.

Future Expansion

This package is intended to grow as additional environmental sensors are supported.

Potential future capabilities include:

• Humidity sensors
• Ambient light sensors
• Air quality sensors
• Carbon dioxide sensors
• Volatile organic compound (VOC) sensors
• Multiple sensor implementations sharing common interfaces

The public interfaces should remain stable while allowing additional hardware implementations to be added without affecting client applications.