Device Data and Configuration

The data published by the device and the configuration options are described in detail in the state JSON schema file for AWS, and Azure. See this state JSON document for an AWS example, and this state JSON document for an Azure example.

Sending and receiving this data is different per cloud-operator, see implementation details for AWS here .

State vs Messages

Most data is stored in the digital twin of the device, this is useful to be able to quickly query the last known data from the device. However some data does not fit well into this model, e.g. because of its ephemeral nature. In the Cat Tracker example we send the button pushes as a message and do not store it in the digital twin; after all it is a UI element and it in case of push buttons has no state which could be restored on the device or persists over a longer time.

The messages published by the device are described in detail in the messages JSON schema file. See this messages JSON document example for an example device state.

Batch data

The firmware may send data as batch, using the schema described in this JSON schema file. See this JSON document for an example batch message.

For sending batched data from the device, the topic <deviceId>/batch is used.

Tracking Modes

The firmware implements two tracking modes: passive and active.

Passive Mode

This is the default mode.

In passive mode the device publishes data based on movement: if it registers movement on the accelerometer, it will publish data. It will wait the amount of seconds configured in cfg.mvres before publishing the next time.

If it detects no movement for the amount of seconds specified in cfg.mvt, it will also publish data once.

The nRF9160 DK (PCA10090) does not support passive mode by default. The passive mode depends on an external accelerometer (Analog Devices ADXL362) being connected to the GPIO ports specified in the nrf9160_pca10090ns.overlay file.

Active Mode

In active mode the device publishes data based on elapsed time. It will wait the amount of seconds configured in cfg.actwt before publishing the next time.

The device can be put in active mode by setting the cfg.act to true.

GPS Timeout configuration

Since the firware currently does not support A-GPS depending on the device location acquiring a GPS fix can take a long time. Therefore a timeout of at least 1000 seconds should be chosen.