hm3301 0.0.2

Python driver for the Seeed HM3301 laser PM2.5 dust sensor (I²C)

hm3301

A Python driver for the Seeed HM3301 laser PM2.5 dust sensor, communicating over I2C.

Features

• Read PM1.0, PM2.5, and PM10 concentrations (standard & atmospheric)
• Read particle counts per 0.1 L in six size bins (0.3 / 0.5 / 1.0 / 2.5 / 5.0 / 10 um)
• Average multiple readings for stability
• AQI category helper (US EPA breakpoints)
• JSON-serialisable data model
• Command-line tool (hm3301-read)
• Typed (PEP 561) and tested

Installation

Requires Python 3.12+.

pip install hm3301

Prerequisites (Raspberry Pi)

sudo apt install python3-smbus i2c-tools
sudo raspi-config   # Interface Options -> I2C -> Enable

Wiring (Raspberry Pi)

HM3301 pin	RPi pin
VCC	3.3 V (pin 1)
GND	GND (pin 6)
SDA	GPIO 2 / SDA (pin 3)
SCL	GPIO 3 / SCL (pin 5)

Quick Start

Python API

from hm3301 import HM3301

with HM3301(i2c_bus=1) as sensor:
    reading = sensor.read()
    print(reading)
    # AirQualityReading(PM1.0=5ug/m3, PM2.5=8ug/m3, PM10=9ug/m3, AQI='Good')

    print(f"PM2.5 = {reading.pm2_5_atm} ug/m3 [{reading.aqi_category}]")

Averaged Readings

with HM3301(i2c_bus=1) as sensor:
    reading = sensor.read_average(samples=10, delay=1.0)
    print(reading.to_dict())

Command-Line Tool

# Single reading
hm3301-read

# Average 5 readings, output as JSON
hm3301-read --samples 5 --json

# Use a different I2C bus or address
hm3301-read --bus 0 --address 0x40

# All options
hm3301-read --help

API Reference

HM3301(i2c_bus=1, i2c_address=0x40)

Method	Description
read()	Return one AirQualityReading
read_average(samples=5, delay=0.5)	Return averaged reading
close()	Release the I2C bus

Supports context manager (with statement).

AirQualityReading

Attribute	Type	Description
pm1_0_std / pm1_0_atm	int	PM1.0 ug/m3
pm2_5_std / pm2_5_atm	int	PM2.5 ug/m3
pm10_std / pm10_atm	int	PM10 ug/m3
count_0_3um ... count_10um	int	Particle counts per 0.1 L
aqi_category	str	US EPA AQI category
timestamp	datetime	Time of reading

Method	Returns	Description
to_dict()	dict	JSON-serialisable dict

Exceptions

Exception	Description
HM3301Error	Base exception
HM3301ConnectionError	I2C bus or sensor unreachable
HM3301ReadError	Read failed or unexpected frame length
HM3301ChecksumError	Frame checksum mismatch

from hm3301 import HM3301, HM3301ConnectionError

try:
    sensor = HM3301(i2c_bus=1)
except HM3301ConnectionError as e:
    print(f"Sensor not found: {e}")

---

Development

Setup

git clone https://github.com/ParthSanepara/hm3301.git
cd hm3301
pip install -e ".[dev]"

Project Structure

src/
  hm3301/
    __init__.py       # Public API exports
    driver.py         # HM3301 I2C driver
    models.py         # AirQualityReading data model
    exceptions.py     # Custom exceptions
    cli.py            # CLI entry point
tests/
    test_driver.py    # Driver tests (mocked I2C)
    test_models.py    # Model + AQI tests

Running Tests

# All tests with coverage
pytest

# Single test
pytest tests/test_models.py::test_aqi_good

# Verbose output
pytest -v

Linting & Type Checking

# Lint
ruff check .

# Lint with auto-fix
ruff check --fix .

# Type check (strict)
mypy .

License

MIT