RT Streaming - Android

TerraRTAndroid

This packages uses Bluetooth Low Energy (BLE) and Bluetooth services. These will be requested as permissions upon initialisation of the package.

The package streams real time data to your backend through WebSockets. You can learn more about it at the Terra WebSocket API guide.

The data streamed to your WebSocket connection will follow the following format:

{
  "op":5,
  "d":
    {
      "ts": <String> (In ISOFormat Date Form)
       "val": <Double>
       "d" <Array<Double>>
    },
    "uid": <String> (user ID)
    "seq": <Int>,
    "t": <String> (Datatype name: Exactly the same as the name of `DataTypes` enum)
}

ts is the timestamp of the record. For each datatype, either val or d is populated. See the Terra Streaming Protocol Reference for full details about the payload format.

Installation

The library is part of mavenCentral! Follow the steps to install:

  1. Open your project in Android Studio.
  2. Navigate to your project's build.gradle file located in the root directory of your project.
  3. Inside the dependencies section of the build.gradle file, add the following line of code. This will add the TerraAndroid SDK as a dependency to your project.
implementation 'co.tryterra:terra-rtandroid:0.4.1'

Usage

The package revolves mainly around a single class: TerraRT.

First, import it into your code:

import co.tryterra.terrartandroid.TerraRT

Then, initialise an instance of the class:

terraRT = TerraRT(
  context: Context = this,
)

Arguments:

  • context: Context => The app context for which you call this function from (usually from a class that extends from Activity types)

Initialising Connections

After initialisation of this class, you can initialise different connections. You can do this as follows:

terraRT.initConnection(token: String, callback: (Boolean) -> Unit)

Arguments:

  • token => an authentication token that should be generated in your backend from the Mobile SDK Token endpoint
  • callback => a function that is called when the initialisation is complete with a boolean depicting if it's successful or not

Upon running this initConnection function, any necessary permission request will be requested.

You may now scan for a device to con

terraRT.startDeviceScan(type: Connections,  useCache: Boolean = false, callback: (Boolean) -> Unit)

Arguments:

  • connection: Connections => This argument takes a Connections enum, indicating the connection you wish to make. This includes BLE, Wear OS (Bluetooth) (Please check out our WearOS SDK for this!), etc. See the Connections Enum reference for a full list
  • useCache parameter can be used if you wish to let the user simply connect the previous connected device.

This will pull a widget up to allow the user to scan and connect to a device.

N.B You will have to download 2 plugins from ANT+ services to use this function, otherwise the connections will return false in the callback (Error logs will be printed). You can find the 2 plugins here: Ant+ Plugins Service and Ant Radio Service

πŸ“˜

For 0.2.x versions and below you can start scans using the following:

  • For Bluetooth/BLE related connections, you will also be required to run
terraRT.startBluetoothScan(type: Connections, callback: (Boolean) -> Unit)

type: Connections => The same Connections enum as before! However this function will only take connections that uses Bluetooth: Connections.BLE and Connections.WEAR_OS

This will cause Bluetooth connection widget will pop up asking you to select the Bluetooth device you wish to connect to. Connecting to any other devices will simply fail if not supported!

The callback is to check whether the connection is successful or not. Please wait for the callback before proceeding!

  • For ANT+ related connections, you can do something similar to BLE connections by running
terraRT.startAntPlusScan(callback: (Boolean) -> Unit)

Streaming Data

Each streaming session requires a token for authentication to Websocket API. This can be generated from the Streaming User Token endpoint. Note: this is a different token from the Mobile SDK token used earlier. The request requires the following fields:

  • dev_id - found at your Terra Dashboard
  • x_api_key - found at your Terra Dashboard
  • user_id - the user_id of the connection you wish to stream

Get the user_id of the current connection as such:

terraRT.getUserId()

Here comes the fun part. You can now start streaming data by running:

terraRT.startRealtime(type: Connections, token: String, dataTypes: DataTypes)

Arguments

  • connection: Connections => This argument takes a Connections enum, indicating the connection you wish to start realtime for
  • token: String => A Streaming User Token for authentication to Websocket API. This can be generated from the Streaming User Token endpoint.
  • dataTypes: DataTypes => This argument takes a DataTypes enum indicating the datatype you wish to stream for.

Similarly, to stop streaming, run the following function:

terraRT.stopRealtime(type: Connections)

N.B Streaming from WEAR OS is handled on the Watch itself!!

Disconnecting

Finally, disconnecting a device is done as:

terraRT.disconnect(type: Connections)