Golioth DC Power Monitor Reference Design

Overview

The Golioth DC Power Monitor is an IoT reference design that includes two channels for monitoring equipment that is powered by Direct Current (DC). This is commonly needed for battery management systems like electric cars or bikes. Having reliable data on the state of the charge/discharge cycles over a period of time makes it possible to perform predictive maintenance and alert when levels are running low.

This reference design uses two ina260 current/voltage/power measurement chips to measure the circuits passing through them. Readings from each channel are passed up to Golioth via a Nordic nRF9160 cellular modem for tracking usage over time. Live "run" time is also reported to show how long a device 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.

The full details of the end-to-end project are available on the Golioth DC Power Monitor Project Page. This includes additional details about:

Supported Hardware

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
	nrf9160dk/nrf9160/ns	nRF9160 DK Follow-Along Guide

Custom Golioth Hardware

Hardware	Zephyr Board	Project Page
	aludel_mini/nrf9160/ns	DC Power Monitor Project Page
	aludel_elixir/nrf9160/ns	Aludel Elixir

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

Use west to initialize and install

cd ~/golioth-reference-design-powermonitor
west init -m git@github.com:golioth/reference-design-powermonitor.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.

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)

Current, Voltage, and Power data for both channels are reported as time-series data on the sensor endpoint. These readings can each be multiplied by 0.00125 to convert the values to Amps, Volts, and Watts.

{
  "sensor": {
    "cur": {
       "ch0": 1,
       "ch1": 292
    },
    "pow": {
      "ch0": 0,
      "ch1": 187
    },
    "vol": {
      "ch0": 4106,
      "ch1": 4110
    }
  }
}

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 desired and actual endpoints.

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

• desired.reset_cumulative values may be changed from the cloud side. The device will recognize when this endpoint is set to true, clearing the stored cumulative values and writing the reset_cumulative value to false to indicate the operation was completed.
• actual values will be updated by the device. The cloud may read the actual endpoints to determine device status, but only the device should ever write to the actual endpoints.

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 Mini

This reference design may be built for the Golioth Aludel Mini board.

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

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-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