The AttNode v3 firmware now has support for the HM3301 particulate matter sensor from Seeed Studios. At the moment the PM1, PM2.5 and PM10 values in µg/m³ for atmospheric environment will be added to the payload if the sensor is connected and enabled.
The sensor can be connected to the regular I2C-pins (Vin, GND, SCL, SDA) and will run from a 3.3V power source. Be aware that the sensor can use up to 120mA of current, so your power source has to be able to provide at least 250mA (combined current of the sensor and the RFM95W while sending).
The firmware support can be enabled with
#define HAS_HM330x in config.h as usual.