Golioth AC Power Monitor Reference Design

Overview

The Golioth AC Power Monitor reference design includes two channels for monitoring electrical equipment. Whether applied to machine tools on a production floor, or the electrical circuits in a commercial/residential setting, having data about electrical usage is a powerful tool for making business decisions.

Readings from each channel are passed up to Golioth for tracking usage over time. Live "run" time is also reported to show how long a machine has currently been running. This data is also used to report the lifetime "run" time of the equipment being monitored. The delay between readings and the threshold at which the equipment is considered "off" are configurable from the Golioth cloud.

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-ac-power-monitor
python -m venv golioth-reference-design-ac-power-monitor/.venv
source golioth-reference-design-ac-power-monitor/.venv/bin/activate
pip install wheel west

Use west to initialize and install

cd ~/golioth-reference-design-ac-power-monitor
west init -m git@github.com:golioth/reference-design-ac-power-monitor.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/cbor-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 CBOR 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:

• Over-the-Air (OTA) firmware updates
• LightDB State for tracking live runtime and cumulative runtime
• LightDB Stream for recording periodic readings from each channel
• Settings Service to adjust the delay between sensor readings and the ADC floor ("off" threshold above which a device will be considered "running")
• Remote Logging
• Remote Procedure call (RPC) to reboot the device or set logging levels

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.

ADC_FLOOR_CH0 (raw ADC value)

ADC_FLOOR_CH1 (raw ADC value)

Filter out noise by adjusting the minimum reading at which a channel will be considered "on".

Default values are 0

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.

reset_cumulative

Reset the cumulative "on time" values stored on the device. After executing, the device will update the cloud's state/cumulative values using the LightDB State service.

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

LightDB State and LightDB Stream data

Time-Series Data (LightDB Stream)

Raw Current data for both channels is reported as time-series data on the sensor endpoint. There readings can each be multiplied by 0.00125 to convert the values to Amps.

{
  "sensor": {
       "ch0": 11,
       "ch1": 447
    }
}

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

Stateful Data (LightDB State)

The concept of Digital Twin is demonstrated with the LightDB State via the state path.

{
  "state": {
    "cumulative": {
      "ch0": 138141,
      "ch1": 1913952
    },
    "live_runtime": {
      "ch0": 0,
      "ch1": 913826
    }
  }
}

• state values will be updated by the device. The cloud may read the state path to determine device status, but only the device should ever write to that path.

Hardware Variations

Nordic nRF9160 DK

This reference design may be built for the Nordic nRF9160 DK.

Use the following commands to build and program. (Use the same console commands from above to provision this board after programming the firmware.)

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

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-Mini
• 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