It's easy to use the PMSA300I and the Adafruit CircuitPython PM25 module. This library allows you to easily write Python code that reads particle concentrations, and particle diameter and the number of particles with different diameters per unit volume.

You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.

CircuitPython Microcontroller Wiring

Wire up a PMSA300I to your board exactly as shown below. Here's an example of wiring a Feather M4 to the sensor with I2C using STEMMA QT and a solderless breadboard.

  • Board 3V to PMSA300I VIN (red wire)
  • Board GND to PMSA300I GND (black wire)
  • Board SCL to PMSA300I SCL (yellow wire)
  • Board SDA to PMSA300I SDA (blue wire)

Python Computer Wiring

Since there's dozens of Linux computers/boards you can use, we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported

Here's the Raspberry Pi wired to the sensor with I2C using STEMMA QT and a solderless breadboard.

  • Pi 3V to PMSA300I VIN (red wire)
  • Pi GND to PMSA300I GND (black wire)
  • Pi SCL to PMSA300I SCL (yellow wire)
  • Pi SDA to PMSA300I SDA (blue wire)

CircuitPython Installation of PM25 Library

You'll need to install the Adafruit CircuitPython PM25 library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle

Our CircuitPython starter guide has a great page on how to install libraries from the bundle.

Load the the following libraries into the lib folder on your CIRCUITPY drive:

  • adafruit_pm25.mpy
  • adafruit_bus_device

Before continuing make sure your board's lib folder or root filesystem has the adafruit_pm25.mpy file and adafruit_bus_device folder copied over.

Next connect to the board's serial console so you are ready to see the example output.

Python Installation of PM25 Library

You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3.

Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!

Once that's done, from your command line run the following command:

pip3 install adafruit-circuitpython-pm25

If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

CircuitPython & Python Usage

To demonstrate the usage of the PMSA300I, we'll use a complete code example to read the particle data.

Save the following code to your CIRCUITPY drive as code.py:

"""
Example sketch to connect to PM2.5 sensor with either I2C or UART.
"""

# pylint: disable=unused-import
import time
import board
import busio
from digitalio import DigitalInOut, Direction, Pull
import adafruit_pm25

reset_pin = None
# If you have a GPIO, its not a bad idea to connect it to the RESET pin
# reset_pin = DigitalInOut(board.G0)
# reset_pin.direction = Direction.OUTPUT
# reset_pin.value = False


# For use with a computer running Windows:
# import serial
# uart = serial.Serial("COM30", baudrate=9600, timeout=1)

# For use with microcontroller board:
# (Connect the sensor TX pin to the board/computer RX pin)
# uart = busio.UART(board.TX, board.RX, baudrate=9600)

# For use with Raspberry Pi/Linux:
# import serial
# uart = serial.Serial("/dev/ttyS0", baudrate=9600, timeout=0.25)

# For use with USB-to-serial cable:
# import serial
# uart = serial.Serial("/dev/ttyUSB0", baudrate=9600, timeout=0.25)

# Connect to a PM2.5 sensor over UART
# pm25 = adafruit_pm25.PM25_UART(uart, reset_pin)

# Create library object, use 'slow' 100KHz frequency!
i2c = busio.I2C(board.SCL, board.SDA, frequency=100000)
# Connect to a PM2.5 sensor over I2C
pm25 = adafruit_pm25.PM25_I2C(i2c, reset_pin)

print("Found PM2.5 sensor, reading data...")

while True:
    time.sleep(1)

    try:
        aqdata = pm25.read()
        # print(aqdata)
    except RuntimeError:
        print("Unable to read from sensor, retrying...")
        continue

    print()
    print("Concentration Units (standard)")
    print("---------------------------------------")
    print(
        "PM 1.0: %d\tPM2.5: %d\tPM10: %d"
        % (aqdata["pm10 standard"], aqdata["pm25 standard"], aqdata["pm100 standard"])
    )
    print("Concentration Units (environmental)")
    print("---------------------------------------")
    print(
        "PM 1.0: %d\tPM2.5: %d\tPM10: %d"
        % (aqdata["pm10 env"], aqdata["pm25 env"], aqdata["pm100 env"])
    )
    print("---------------------------------------")
    print("Particles > 0.3um / 0.1L air:", aqdata["particles 03um"])
    print("Particles > 0.5um / 0.1L air:", aqdata["particles 05um"])
    print("Particles > 1.0um / 0.1L air:", aqdata["particles 10um"])
    print("Particles > 2.5um / 0.1L air:", aqdata["particles 25um"])
    print("Particles > 5.0um / 0.1L air:", aqdata["particles 50um"])
    print("Particles > 10 um / 0.1L air:", aqdata["particles 100um"])
    print("---------------------------------------")

If you haven't already, connect to the serial console to see the example output.

That's all there is to reading air quality data from the PSMA300I!

This guide was first published on Jul 22, 2020. It was last updated on Jul 22, 2020.
This page (Python & CircuitPython) was last updated on Sep 18, 2020.