Golioth DC Power Monitor Reference Design

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.

Business use cases and hardware build details are available on the DC Power Monitor Project Page.

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

Supported Hardware

• Nordic nRF9160-DK
• Golioth Aludel Elixir
• Golioth Aludel Mini

Additional Sensors/Components

• Texas Instruments INA260 current/voltage/power monitor (x2)

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.

• 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 path. These readings can each be multiplied by 0.00125 to convert the values to Amps, Volts, and Watts.

• sensor/cur/ch0: Current for channel 0
• sensor/cur/ch0: Current for channel 1
• sensor/pow/ch0: Power for channel 0
• sensor/pow/ch0: Power for channel 1
• sensor/vol/ch0: Voltage for channel 0
• sensor/vol/ch0: Voltage for channel 1

{
  "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.

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 via the desired and actual endpoints.

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

• desired/reset_cumulative values may be changed from the cloud side. The device will recognize when this path is set to true, clearing the stored cumulative values and writing the reset_cumulative value to false to indicate the operation was completed.
• state/cumulative values indicate the sum of all time a current is detected on a channel throughout all on/off cycles.
• state/live_runtime values reflect the time a current has been continuously detected on the channel since the state of the equipment being monitored changed from "off" to "on".

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

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

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.

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-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

Have Questions?

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