nRF Cloud

The nRF Cloud library enables applications to connect to Nordic Semiconductor’s nRF Cloud. It abstracts and hides the details of the transport and the encoding scheme that is used for the payload and provides a simplified API interface for sending data from supported sensor types to the cloud. The current implementation supports the following technology:

  • GPS and FLIP sensor data

  • TLS secured MQTT as the communication protocol

  • JSON as the data format

Initializing

Before using any other APIs of the module, the application must call nrf_cloud_init(). If this API fails, the application must not use any APIs of the module.

Note

Initialize the module before starting any timers, sensor drivers, or communication on the link.

Connecting

The application can use nrf_cloud_connect() to connect to the cloud. This API triggers a series of events and actions in the system. If the API fails, the application must retry to connect.

First, the library tries to establish the transport for communicating with the cloud. This procedure involves a TLS handshake that might take up to three seconds. The API blocks for the duration of the handshake.

Next, the API subscribes to an MQTT topic to start receiving user association requests from the cloud. The cloud uses the device’s certificates for authentication. See nRF Connect for Cloud Certificate Update and the Modem key management library for more information on modem credentials. The certificates are generated using the device’s ID and PIN/HWID.

Every time nRF Cloud starts a communication session with a device, it verifies whether the device is uniquely associated with a user. If not, the user association procedure is triggered. When adding the device to an nRF cloud account, the user must provide the correct device ID and PIN (for Thingy:91) or HWID (for nRF9160 DK) to nRF Cloud.

The following message sequence chart shows the flow of events and expected application responses to each event during the user association procedure:

msc {
hscale = "1.3";
Module,Application;
Module<<Application      [label="nrf_cloud_connect() returns successfully"];
Module>>Application      [label="NRF_CLOUD_EVT_TRANSPORT_CONNECTED"];
Module>>Application      [label="NRF_CLOUD_EVT_USER_ASSOCIATION_REQUEST"];
 ---                     [label="Add the device to nRF Cloud account"];
Module>>Application      [label="NRF_CLOUD_EVT_USER_ASSOCIATED"];
Module<<Application      [label="nrf_cloud_disconnect() returns successfully"];
Module>>Application      [label="NRF_CLOUD_EVT_TRANSPORT_DISCONNECTED"];
Module<<Application      [label="nrf_cloud_connect() returns successfully"];
Module>>Application      [label="NRF_CLOUD_EVT_TRANSPORT_CONNECTED"];
Module>>Application      [label="NRF_CLOUD_EVT_USER_ASSOCIATED"];
Module>>Application      [label="NRF_CLOUD_EVT_READY"];
}

Note

This chart shows the sequence of successful user association of an unassociated device. Currently, nRF Cloud requires that communication is re-established to update the device’s permission to send user data. The application must disconnect using nrf_cloud_disconnect() and then reconnect using nrf_cloud_connect().

When the device is successfully associated with a user on the cloud, subsequent connections to the cloud (also across power cycles) follow this sequence:

msc {
hscale = "1.3";
Module,Application;
Module<<Application      [label="nrf_cloud_connect() returns successfully"];
Module>>Application      [label="NRF_CLOUD_EVT_TRANSPORT_CONNECTED"];
Module>>Application      [label="NRF_CLOUD_EVT_USER_ASSOCIATED"];
Module>>Application      [label="NRF_CLOUD_EVT_READY"];
}

After receiving NRF_CLOUD_EVT_READY, the application can start sending sensor data to the cloud.

Sending sensor data

The library offers two APIs, nrf_cloud_sensor_data_send() and nrf_cloud_sensor_data_stream(), for sending sensor data to the cloud. Currently, the supported sensor types are GPS and FLIP (see nrf_cloud_sensor).

Use nrf_cloud_sensor_data_stream() to send sensor data with best quality.

Before sending any sensor data, call the function nrf_cloud_sensor_attach() with the type of the sensor. Note that this function must be called after receiving the event NRF_CLOUD_EVT_READY. It triggers the event NRF_CLOUD_EVT_SENSOR_ATTACHED if the execution was successful.

Using Cloud API with nRF Cloud library

You can use this library in conjunction with Cloud API. The following sections describe the various stages in the process of connection to the nRF Cloud.

Initialization

To use a defined Cloud API backend, a binding must be obtained using the Cloud API function cloud_get_binding() to which you can pass the name of the desired backend. The nRF Cloud library defines the Cloud API backend as NRF_CLOUD via the CLOUD_BACKEND_DEFINE macro.

The backend must be initialized using the cloud_init() function, with the binding, and a function pointer to user defined Cloud API event handler as parameters. If cloud_init() returns success, the backend is ready for use. The return values for a failure scenario of the cloud_init() function are described below for the nRF Cloud backend:

  • -EACCES: invalid state; already initialized

  • -EINVAL: invalid event handler provided

  • -ENOMEM: error building MQTT topics; the given client ID of the device could be too long

Note

If CONFIG_NRF_CLOUD_PROVISION_CERTIFICATES is enabled, error values could be different or have different error descriptions.

Connecting to the Cloud

The nRF Cloud library offers two ways to handle backend connections when the cloud_connect() function is called. If the CONFIG_NRF_CLOUD_CONNECTION_POLL_THREAD Kconfig option is enabled, a cloud backend thread monitors the connection socket. If the option is not enabled, the user application is responsible for monitoring the socket.

The dual functionalities of the cloud_connect() function in the two scenarios are described below:

CONFIG_NRF_CLOUD_CONNECTION_POLL_THREAD enabled

Function does not block and returns success if the connection monitoring thread has started. Below are some of the error codes that can be returned:

Upon success, the monitoring thread sends an event of type CLOUD_EVT_CONNECTING to the user’s cloud event handler, with the err field set to success. If an error occurs, another event of the same type is sent, with the err field set to indicate the cause. These additional errors are described in the following section.

CONFIG_NRF_CLOUD_CONNECTION_POLL_THREAD disabled

Function blocks and returns success when the MQTT connection to the cloud has completed. The connection socket is set in the backend binding and it becomes available for the application to use. Below are some of the error codes that can be returned:

For both connection methods, when a device with JITP certificates attempts to connect to nRF Cloud for the first time, the cloud rejects the connection attempt so that it can provision the device. When this occurs, the Cloud API generates a CLOUD_EVT_DISCONNECTED event with the err field set to CLOUD_DISCONNECT_INVALID_REQUEST. The device should restart the connection process upon receipt of the CLOUD_EVT_DISCONNECTED event.

Connected to the Cloud

When the connection between the device and the cloud has been successfully established, the Cloud API dispatches a CLOUD_EVT_CONNECTED event. If the device is not associated with an nRF Cloud account, a CLOUD_EVT_PAIR_REQUEST event is generated. The device must wait until it is added to an account, which is indicated by the CLOUD_EVT_PAIR_DONE event. If a device pair request is received, the device must disconnect and reconnect after receiving the CLOUD_EVT_PAIR_DONE event. This is necessary because the updated policy of the cloud becomes effective only on a new connection. Following the CLOUD_EVT_PAIR_DONE event, the Cloud API sends a CLOUD_EVT_READY event to indicate that the cloud is ready to receive data from the device.

Disconnection from the Cloud

The user application can generate a disconnect request with the cloud_disconnect() function. A successful disconnection is indicated by the CLOUD_EVT_DISCONNECTED event. The err field in the event message is set to CLOUD_DISCONNECT_USER_REQUEST. If an unexpected disconnect event is received, the err field contains the cause. If CONFIG_NRF_CLOUD_CONNECTION_POLL_THREAD is not enabled, the only cause of disconnection is CLOUD_DISCONNECT_MISC. The user application should use the connection socket to determine a reason.

If the socket is being monitored by the backend thread, the following causes of disconnection can occur:

API documentation

Header file: include/net/nrf_cloud.h
Source files: subsys/net/lib/nrf_cloud/src/
group nrf_cloud

Typedefs

typedef void (*nrf_cloud_event_handler_t)(const struct nrf_cloud_evt *evt)

Event handler registered with the module to handle asynchronous events from the module.

Parameters
  • [in] evt: The event and any associated parameters.

Enums

enum nrf_cloud_evt_type

Asynchronous nRF Cloud events notified by the module.

Values:

NRF_CLOUD_EVT_TRANSPORT_CONNECTED = 0x1

The transport to the nRF Cloud is established.

NRF_CLOUD_EVT_USER_ASSOCIATION_REQUEST

There was a request from nRF Cloud to associate the device with a user on the nRF Cloud.

NRF_CLOUD_EVT_USER_ASSOCIATED

The device is successfully associated with a user.

NRF_CLOUD_EVT_READY

The device can now start sending sensor data to the cloud.

NRF_CLOUD_EVT_SENSOR_ATTACHED

A sensor was successfully attached to the cloud. Supported sensor types are defined in nrf_cloud_sensor.

NRF_CLOUD_EVT_RX_DATA

The device received data from the cloud.

NRF_CLOUD_EVT_SENSOR_DATA_ACK

The data sent to the cloud was acknowledged.

NRF_CLOUD_EVT_TRANSPORT_DISCONNECTED

The transport was disconnected.

NRF_CLOUD_EVT_FOTA_DONE

The device should be restarted to apply a firmware upgrade

NRF_CLOUD_EVT_ERROR = 0xFF

There was an error communicating with the cloud.

enum nrf_cloud_sensor

Sensor types supported by the nRF Cloud.

Values:

NRF_CLOUD_SENSOR_GPS

The GPS sensor on the device.

NRF_CLOUD_SENSOR_FLIP

The FLIP movement sensor on the device.

NRF_CLOUD_SENSOR_BUTTON

The Button press sensor on the device.

NRF_CLOUD_SENSOR_TEMP

The TEMP sensor on the device.

NRF_CLOUD_SENSOR_HUMID

The Humidity sensor on the device.

NRF_CLOUD_SENSOR_AIR_PRESS

The Air Pressure sensor on the device.

NRF_CLOUD_SENSOR_AIR_QUAL

The Air Quality sensor on the device.

The RSPR data obtained from the modem.

NRF_CLOUD_DEVICE_INFO

The descriptive DEVICE data indicating its status.

Functions

int nrf_cloud_init(const struct nrf_cloud_init_param *param)

Initialize the module.

Warning

This API must be called exactly once, and it must return successfully.

Parameters
  • [in] param: Initialization parameters.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_connect(const struct nrf_cloud_connect_param *param)

Connect to the cloud.

In any stage of connecting to the cloud, an NRF_CLOUD_EVT_ERROR might be received. If it is received before NRF_CLOUD_EVT_TRANSPORT_CONNECTED, the application may repeat the call to nrf_cloud_connect to try again.

Parameters
  • [in] param: Parameters to be used for the connection.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_sensor_attach(const struct nrf_cloud_sa_param *param)

Attach a sensor to the cloud.

This API should only be called after receiving an NRF_CLOUD_EVT_READY event. If the API succeeds, wait for the NRF_CLOUD_EVT_SENSOR_ATTACHED event before sending the sensor data.

Parameters
  • [in] param: Sensor information.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_sensor_data_send(const struct nrf_cloud_sensor_data *param)

Send sensor data reliably.

This API should only be called after receiving an NRF_CLOUD_EVT_SENSOR_ATTACHED event. If the API succeeds, you can expect the NRF_CLOUD_EVT_SENSOR_DATA_ACK event.

Parameters
  • [in] param: Sensor data.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_shadow_update(const struct nrf_cloud_sensor_data *param)

Update the device shadow with sensor data.

Parameters
  • [in] param: Sensor data.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_sensor_data_stream(const struct nrf_cloud_sensor_data *param)

Stream sensor data.

This API should only be called after receiving an NRF_CLOUD_EVT_SENSOR_ATTACHED event.

Parameters
  • [in] param: Sensor data.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

int nrf_cloud_disconnect(void)

Disconnect from the cloud.

This API may be called any time after receiving the NRF_CLOUD_EVT_TRANSPORT_CONNECTED event. If the API succeeds, you can expect the NRF_CLOUD_EVT_TRANSPORT_DISCONNECTED event.

Return Value
  • 0: If successful. Otherwise, a (negative) error code is returned.

void nrf_cloud_process(void)

Function that must be called periodically to keep the module functional.

struct nrf_cloud_data
#include <nrf_cloud.h>

Generic encapsulation for any data that is sent to the cloud.

Public Members

uint32_t len

Length of the data.

const void *ptr

Pointer to the data.

struct nrf_cloud_topic
#include <nrf_cloud.h>

MQTT topic.

Public Members

uint32_t len

Length of the topic.

const void *ptr

Pointer to the topic.

struct nrf_cloud_sensor_list
#include <nrf_cloud.h>

Sensors that are supported by the device.

Public Members

uint8_t size

Size of the list.

nrf_cloud_sensor *ptr

Supported sensor types.

struct nrf_cloud_connect_param
#include <nrf_cloud.h>

Connection parameters.

Public Members

const struct nrf_cloud_sensor_list *sensor

Supported sensor types. May be NULL.

struct nrf_cloud_sa_param
#include <nrf_cloud.h>

Parameters of attached sensors.

Public Members

nrf_cloud_sensor sensor_type

The sensor that is being attached.

struct nrf_cloud_sensor_data
#include <nrf_cloud.h>

Sensor data transmission parameters.

Public Members

nrf_cloud_sensor type

The sensor that is the source of the data.

struct nrf_cloud_data data

Sensor data to be transmitted.

uint32_t tag

Unique tag to identify the sent data. Useful for matching the acknowledgment.

struct nrf_cloud_evt
#include <nrf_cloud.h>

Asynchronous events received from the module.

Public Members

nrf_cloud_evt_type type

The event that occurred.

uint32_t status

Any status associated with the event.

struct nrf_cloud_data data

Received data.

struct nrf_cloud_topic topic

Topic on which data was received.

struct nrf_cloud_init_param
#include <nrf_cloud.h>

Initialization parameters for the module.

Public Members

nrf_cloud_event_handler_t event_handler

Event handler that is registered with the module.