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Dustnet Node

This is the firmware for a dustnet-node. It has been build especially for the Dustmap project. It uses LoRaWAN and The Things Network (short: TTN) to transmit sensor measurements.

This documentation is a work-in-progress.

This open source project has been generously supported by netidee.

Hardware

A dustmap-node is usually equipped with an air quality sensor (SDS011) and a temperature and humidity sensor (DHT22).

Software

The firmware can be installed on most Arduino-compatible devices. For the Dustmap-project we use a custom board based on the Arduino Pro Mini.

Configuration

The configuration can be found in the config.h file. Please be advised that we do not recommend to change anything in here. Except you know exactly, what you are doing. Than you will properly be fine.

Key Description
ENABLE_DEBUG Enables debug output via serial interface. This will significantly increase the filesize. Uncomment to enable
APPEUI The Things Network Application EUI. See The Things Network Integration for more information.
DEVEUI The Things Network Device EUI. See The Things Network Integration for more information.
APPKEY The Things Network Application Key. See The Things Network Integration for more information.
TX_INTERVAL Delay in seconds between measurements. Default: 600
MEASSURE_INTERVAL Delay in seconds between samples of one measurement. Default: 5
SAMPLE_COUNT Number of samples taken during one measurement. Default: 11
SDS011_PIN_RX Pin mapping for RX-pin of the SDS011 Default: 8
SDS011_PIN_TX Pin mapping for TX-pin of the SDS011 Default: 9
DHT22_PIN Pin mapping for the DHT22 Default: 2
LMIC_PIN_NSS
LMIC_PIN_DIO

To compile this code, you need to have the Arduino-LMIC library by Matthijs Kooijman installed. We recommend to check it out directly from Github as using "Manage Libraries..." in the Arduino IDE will most likely fail.

The Things Network Integration

To contribute data to the dustmap project, you need to obtain DevEUI, AppEUI and AppKey from the dustmap API. See Expert-Mode if you want to use this firmware with your own TTN application.

Expert-Mode: Setup your own The Things Network Application To use this firmware in Expert-Mode you have to setup your own TTN-application.

Decoder & Converter

Sensor values are converted into int and packed into bytes. The following functions will help you to convert them back into useful values. If you plan on using your node with the provided AppEUI and AppKey, you can safely ignore this part.

Payload decoder function for the TTN applications:

function Decoder(bytes, port) {
    // Decode bytes to number
    // - First byte: Battery State
    // - Second + Third byte: PM2.5 Sensor value
    // - Fourth + Fifth byte: PM10 Sensor value
    // - sixth + seventh byte: Humidity & Temperature Sensor value

    var batteryInt = bytes[0];
    var sensorPM25Int = (bytes[1] << 8) | bytes[2];
    var sensorPM10Int = (bytes[3] << 8) | bytes[4];
    var sensorHumidityInt = bytes[5] & 0x7F;
    var sensorTemperatureInt = ((bytes[5] >> 7) & 0x1) | (bytes[6] << 1);

    return {
        battery: batteryInt,
        sensorPM25: sensorPM25Int,
        sensorPM10: sensorPM10Int,
        sensorHumidity: sensorHumidityInt,
        sensorTemperature: sensorTemperatureInt,
    };
}

Payload converter function for the TTN applications:

function Converter(decoded, port) {
    decoded.sensorPM25 = Math.round(decoded.sensorPM25 / 10);
    decoded.sensorPM10 = Math.round(decoded.sensorPM10 / 10);

    // Map temperature from 0-512 to -40-80°C
  	decoded.sensorTemperature = Math.round((decoded.sensorTemperature - 0) * (800 - (-400)) / (512 - 0) + (-400));
  	decoded.sensorTemperature /= 10;

  	return decoded;
}

Licence

Copyright 2018 Dustmap.org. All rights reserved.

This work is licensed under the terms of the MIT license. For a copy, see https://opensource.org/licenses/MIT.