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Air Quality Monitor Reference Design

This repository contains the firmware source code and pre-built release firmware images for the Golioth Air Quality Monitor reference design.

The full project details are available on the Air Quality Monitor Project Page, including follow-along guides for building an IoT Air Quality Monitor yourself using widely available off-the-shelf development boards.

We call this Follow-Along Hardware, and we think it's one of the quickest and easiest ways to get started building an IoT proof-of-concept with Golioth. In the follow-along guides, you will learn how to assemble the hardware, flash a pre-built firmware image onto the device, and connect to the Golioth cloud in minutes.

Once you have completed a follow-along guide for one of our supported hardware platforms, the instructions below will walk you through how to build and configure the firmware yourself.

Supported Hardware

This firmware can be built for a variety of supported hardware platforms.

Important

In Zephyr, each of these different hardware variants is given a unique "board" identifier, which is used by the build system to generate firmware for that variant.

When building firmware using the instructions below, make sure to use the correct Zephyr board identifier that corresponds to your follow-along hardware platform.

Follow-Along Hardware
Hardware Zephyr Board Follow-Along Guide
images/air_quality_monitor_fah_nrf9160_dk.jpg nrf9160dk_nrf9160_ns nRF9160 DK Follow-Along Guide
Custom Golioth Hardware
Hardware Zephyr Board Project Page
images/air_quality_monitor_aludel_mini_v1_photo_top.jpg aludel_elixir_ns Air Quality Monitor Project Page

Firmware Overview

This reference design firmware 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)

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

Use west to initialize and install

cd ~/golioth-reference-design-air-quality
west init -m [email protected]: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.

Important

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

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.

Golioth Features

This app implements:

Settings Service

The following settings can 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).

LightDB Stream Service

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)

On hardware platforms with support for battery monitoring, battery voltage and level readings are periodically sent to the following battery/* endpoints:

  • battery/batt_v: Battery Voltage (V)
  • battery/batt_lvl: Battery Level (%)

LightDB State Service

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

  • desired values may be changed from the cloud side. The device will recognize these, validate them for [0..65535] bounding, and then reset these endpoints to -1
  • state values will be updated by the device whenever a valid value is received from the desired endpoints. The cloud may read the state endpoints to determine device status, but only the device should ever write to the state endpoints.

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.

Hardware Variations

This reference design may be built for a variety of different boards.

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.

Golioth Aludel Elixir

This reference design may be built for the Golioth Aludel Elixir board. By default this will build for the latest hardware revision of this board.

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

To build for a specific board revision (e.g. Rev A) add the revision suffix @<rev>.

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

OTA Firmware Update

This application includes the ability to perform Over-the-Air (OTA) firmware updates:

  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 an artifact for your Golioth project using main as the package name.
  3. Create and roll out a release based on this artifact.

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

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