Golioth Air Quality Monitor Reference Design

The Air Quality Monitor demonstrates how to measure ambient air quality within an indoor environment using the Golioth IoT platform. Specifically, the following environmental parameters can be monitored:

• 🦠 Airborne particulate matter (μg/m³ and #/cm³)
• 😷 CO₂ (ppm)
• 💦 Relative humidity (%RH)
• 🌡️ Temperature (°C)
• 💨 Pressure (kPa)

From the Golioth web console you may view data, deploy OTA firmware updates, adjust device Settings, and issue Remote Procedure Calls (RPCs).

Business use cases and hardware build details are available on the Air Quality Monitor Project Page.

This repository contains the firmware source code and pre-built release firmware images.

Supported Hardware

• Nordic nRF9160-DK
• Golioth Aludel Elixir

Additional Sensors/Components

• Sensirion SCD41 carbon dioxide sensor
• Sensirion SPS30 particulate matter sensor
• Bosch BME280 digital humidity, pressure, and temperature sensor

Golioth Features

This app implements:

• Device Settings Service
• Remote Procedure Call (RPC)
• Stream Client
• LightDB State Client
• Over-the-Air (OTA) Firmware Upgrade
• Backend Logging

Settings Service

The following settings should be set in the Device Settings menu of the Golioth Console.

• LOOP_DELAY_S Adjusts the delay between sensor readings. Set to an integer value (seconds).

  Default value is 60 seconds.

• CO2_SENSOR_TEMPERATURE_OFFSET Adjusts the temperature offset setting for the SCD4x CO₂ sensor. Set to an integer value (milli °C).

  Default value is 0 m°C.

• CO2_SENSOR_ALTITUDE Adjusts the altitude setting for the SCD4x CO₂ sensor. Set to an integer value(meters above sea level).

  Default value is 0 meters.

• CO2_SENSOR_ASC_ENABLE Enables or disables the automatic self-calibration setting for the SCD4x CO₂ sensor. Set to a boolean value.

  Default value is true.

• PM_SENSOR_SAMPLES_PER_MEASUREMENT Adjusts the number of samples averaged together when fetching a measurement from the particulate matter sensor. Set to an integer value (samples).

  Note that each sample requires ~1s to fetch, so there is a tradeoff between getting a good average sample and the time required to fetch the measurement.

  Default value is 30 samples per measurement.

• PM_SENSOR_AUTO_CLEANING_INTERVAL Adjusts the automatic fan cleaning interval setting for the SPS30 particulate matter sensor. Set to an integer value (seconds).

  Default value is 604800 seconds (168 hours or 1 week).

Remote Procedure Call (RPC) Service

The following RPCs can be initiated in the Remote Procedure Call menu of the Golioth Console.

• get_network_info Query and return network information.

• reboot Reboot the system.

• set_log_level Set the log level.

  The method takes a single parameter which can be one of the following integer values:

  • 0: LOG_LEVEL_NONE
  • 1: LOG_LEVEL_ERR
  • 2: LOG_LEVEL_WRN
  • 3: LOG_LEVEL_INF
  • 4: LOG_LEVEL_DBG

• clean_pm_sensor Initiate the SPS30 particulate matter fan-cleaning procedure manually. The fan cleaning procedure takes approximately 10s to complete.

• reset_pm_sensor Reset the SPS30 particulate matter sensor.

Time-Series Stream data

Sensor data is periodically sent to the following sensor/* endpoints of the LightDB Stream service:

• sensor/tem: Temperature (°C)
• sensor/pre: Pressure (kPa)
• sensor/hum: Humidity (%RH)
• sensor/co2: CO₂ (ppm)
• sensor/mc_1p0: Particulate Matter Mass Concentration 1.0 (μg/m³)
• sensor/mc_2p5: Particulate Matter Mass Concentration 2.5 (μg/m³)
• sensor/mc_4p0: Particulate Matter Mass Concentration 4.0 (μg/m³)
• sensor/mc_10p0: Particulate Matter Mass Concentration 10.0 (μg/m³)
• sensor/nc_0p5: Particulate Matter Number Concentration 0.5 (#/cm³)
• sensor/nc_1p0: Particulate Matter Number Concentration 1.0 (#/cm³)
• sensor/nc_2p5: Particulate Matter Number Concentration 2.5 (#/cm³)
• sensor/nc_4p0: Particulate Matter Number Concentration 4.0 (#/cm³)
• sensor/nc_10p0: Particulate Matter Number Concentration 10.0 (#/cm³)
• sensor/tps: Typical Particle Size (μm)

{
  "sensor": {
    "co2": 1419,
    "hum": 35.804687,
    "mc_10p0": 0.117215,
    "mc_1p0": 0.110846,
    "mc_2p5": 0.117215,
    "mc_4p0": 0.117215,
    "nc_0p5": 0.748922,
    "nc_10p0": 0.885024,
    "nc_1p0": 0.881767,
    "nc_2p5": 0.884648,
    "nc_4p0": 0.884848,
    "pre": 98.689242,
    "tem": 23.01,
    "tps": 0.439595
  }
}

If your board includes a battery, voltage and level readings will be sent to the battery path.

Note

Your Golioth project must have a Pipeline enabled to receive this data. See the Add Pipeline to Golioth section below.

Stateful Data (LightDB State)

The concept of Digital Twin is demonstrated with the LightDB State example_int0 and example_int1 variables that are subpaths of the desired and state paths.

• desired values may be changed from the cloud side. The device will recognize these, validate them for [0..65535] bounding, and then reset these values to -1
• state values will be updated by the device to reflect the device's actual stored value. The cloud may read the state endpoints to determine device status. In this arrangement, only the device should ever write to the state endpoints.

{
  "desired": {
    "example_int0": -1,
    "example_int1": -1
  },
  "state": {
    "example_int0": 0,
    "example_int1": 1
  }
}

By default the state values will be 0 and 1. Try updating the desired values and observe how the device updates its state.

OTA Firmware Update

This application includes the ability to perform Over-the-Air (OTA) firmware updates. To do so, you need a binary compiled with a different version number than what is currently running on the device.

Note

If a newer release is available than what your device is currently running, you may download the pre-compiled binary that ends in _update.bin and use it in step 2 below.

1. Update the version number in the VERSION file and perform a pristine (important) build to incorporate the version change.

2. Upload the build/app/zephyr/zephyr.signed.bin file as a Package for your Golioth project.

   • Use main as the package name.
   • Use the same version number from step 1.

3. Create a Cohort and add your device to it.

4. Create a Deployment for your Cohort using the package name and version number from step 2.

5. Devices in your Cohort will automatically upgrade to the most recently deployed firmware.

Visit the Golioth Docs OTA Firmware Upgrade page for more info.

Add Pipeline to Golioth

Golioth uses Pipelines to route stream data. This gives you flexibility to change your data routing without requiring updated device firmware.

Whenever sending stream data, you must enable a pipeline in your Golioth project to configure how that data is handled. Add the contents of pipelines/json-to-lightdb.yml as a new pipeline as follows (note that this is the default pipeline for new projects and may already be present):

1. Navigate to your project on the Golioth web console.
2. Select Pipelines from the left sidebar and click the Create button.
3. Give your new pipeline a name and paste the pipeline configuration into the editor.
4. Click the toggle in the bottom right to enable the pipeline and then click Create.

All data streamed to Golioth in JSON format will now be routed to LightDB Stream and may be viewed using the web console. You may change this behavior at any time without updating firmware simply by editing this pipeline entry.

Local set up

Important

Do not clone this repo using git. Zephyr's west meta tool should be used to set up your local workspace.

Install the Python virtual environment (recommended)

cd ~
mkdir golioth-reference-design-air-quality
python -m venv golioth-reference-design-air-quality/.venv
source golioth-reference-design-air-quality/.venv/bin/activate
pip install wheel west ecdsa

Use west to initialize and install

cd ~/golioth-reference-design-air-quality
west init -m git@github.com:golioth/reference-design-air-quality.git .
west update
west zephyr-export
pip install -r deps/zephyr/scripts/requirements.txt

Building the application

Build the Zephyr sample application for the Nordic nRF9160 DK (nrf9160dk_nrf9160_ns) from the top level of your project. After a successful build you will see a new build directory. Note that any changes (and git commits) to the project itself will be inside the app folder. The build and deps directories being one level higher prevents the repo from cataloging all of the changes to the dependencies and the build (so no .gitignore is needed).

Prior to building, update VERSION file to reflect the firmware version number you want to assign to this build. Then run the following commands to build and program the firmware onto the device.

Warning

You must perform a pristine build (use -p or remove the build directory) after changing the firmware version number in the VERSION file for the change to take effect.

$ (.venv) west build -p -b nrf9160dk/nrf9160/ns --sysbuild app
$ (.venv) west flash

Configure PSK-ID and PSK using the device shell based on your Golioth credentials and reboot:

uart:~$ settings set golioth/psk-id <my-psk-id@my-project>
uart:~$ settings set golioth/psk <my-psk>
uart:~$ kernel reboot cold

External Libraries

The following code libraries are installed by default. If you are not using the custom hardware to which they apply, you can safely remove these repositories from west.yml and remove the includes/function calls from the C code.

• golioth-zephyr-boards includes the board definitions for the Golioth Aludel-Elixir
• libostentus is a helper library for controlling the Ostentus ePaper faceplate
• zephyr-network-info is a helper library for querying, formatting, and returning network connection information via Zephyr log or Golioth RPC

Have Questions?

Please get in touch with Golioth engineers by starting a new thread on the Golioth Forum.