Using Bluetooth Low Energy Devices with Flutter Capture

Device Manager

The Socket Mobile devices use Bluetooth Low Energy (D600, S550. S370 and S320) to communicate with the host.

CaptureSDK provides a new Device Manager object in order to provide some control over the Bluetooth Low Energy transport.

The Device Manager UUID and reference are received in the 2 notifications CaptureEventIds.DeviceManagerArrival and CaptureEventIds.DeviceManagerRemoval.

Here is an example of such a notification in a sample app:

_onCaptureEvent(e, handle) {

    if (e == null) {
      return;
    } else if (e.runtimeType == CaptureException) {
      print("${e.code}" + ': ' + e.message;
      return;
    }

    logger.log('onCaptureEvent from: ', '$handle');

    switch (e.id) {
      case CaptureEventIds.DeviceManagerArrival:
        print('Open the device: ' + event.value.guid);

        setState(() {
            _deviceCapture = deviceCapture;
        });

        try {
            dynamic res = await captureDevice.openDevice(event.value.guid, capture);
            print('opening device returns: ' + result);
            CaptureProperty property = new CaptureProperty(
                CapturePropertyIds.Favorite,
                CapturePropertyTypes.none,
                {}
            );
            try {
                dynamic response = await captureDevice.getProperty(property);
                if (favorite.length === 0) {
                  CaptureProperty property = new CaptureProperty(
                    CapturePropertyIds.Favorite,
                    CapturePropertyTypes.String,
                    '*'
                  );

                  return captureDeviceManager.setProperty(property);
                }
            } catch (err){
                print(err);
            }

        break;
      ...
    }
  }

In this example the assumptions are a capture reference set to the main capture is already open with the app credentials, and the captureDeviceManager is declared in a scope accessible to this Capture notification handler.

Favorite Devices

To facilitate the operations of discovering and connecting to a Bluetooth Low Energy device, a concept of favorite devices has been introduced.

The Device Manager has a property to configure in a persistent way the favorite devices.

As soon as the Device Manager favorite devices is set to either a device identifier or "*" the auto discovery and connect mode starts automatically.

In this mode, the Device Manager starts a discovery and connects to the device corresponding to the identifier found in the favorite devices property or to the first device it finds in the case where the favorite devices is set to "*".

Note

Using auto discovery and connect mode can increase power consumption. Once the device is connected, the consumption level drops. But as soon as the discovery restarts when, for example when the device is no longer ON or in range, then the power consumption increases slightly. Setting the favorite devices to an empty string will stop the auto discovery and connect mode, and Bluetooth Low Energy discovery won’t happen again until the favorite devices is set or the discovery is implicitly started by using the Bluetooth Low Energy Device Manager startDiscovery property.

Starting Bluetooth Low Energy Devices Auto Discovery Mode

The following code sample shows how to turn on by default in an app the auto discovery and connect mode to support device, so that as soon as there is a device turned on in the vicinity, the app will automatically connect to it:

_onCaptureEvent(e, handle) {

    if (e == null) {
      return;
    } else if (e.runtimeType == CaptureException) {
      print("${e.code}" + ': ' + e.message;
      return;
    }

    logger.log('onCaptureEvent from: ', '$handle');

    switch (e.id) {
      case CaptureEventIds.DeviceManagerArrival:
        print('Open the device: ' + event.value.guid);

        setState(() {
            _deviceCapture = deviceCapture;
        });

        try {
            dynamic res = await captureDevice.openDevice(event.value.guid, capture);
            print('opening device returns: ' + result);
            CaptureProperty property = new CaptureProperty(
                CapturePropertyIds.FavoriteDevice,
                CapturePropertyTypes.none,
                {}
            );
            try {
                dynamic response = await captureDevice.getProperty(property);
                if (favorite.length === 0) {
                  CaptureProperty property = new CaptureProperty(
                    CapturePropertyIds.FavoriteDevice,
                    CapturePropertyTypes.String,
                    '*'
                  );

                  return captureDeviceManager.setProperty(property);
                }
            } catch (err){
                print(err);
            }

        break;
      ...
    }
  }

To turn off this feature, just set the favorite devices to an empty string:

const property = new CaptureProperty(
  SocketMobile.CapturePropertyIds.FavoriteDevice,
  SocketMobile.CapturePropertyTypes.String,
  ''
);

try {
  dynamic result = await deviceCapture.setProperty(property)
  print('device manager favorite has been reset')
} on CaptureException catch (exception){
  print('error while setting device manager favorite: ' + exception.code.toString() + ': ' + exception.message);
}

Presence of a Bluetooth Low Energy Device

The presence of device reference is handled by the application by handling in the notification handler, the ids CaptureEventIds.DeviceArrival and CaptureEventIds.DeviceRemoval indicate if a device has been connected and ready or when a device has disconnected and is no longer available.

Note

These CaptureEventIds.DeviceArrival and CaptureEventIds.DeviceRemoval events are received for any Socket Mobile device connects or disconnects from the host. The device type parameter helps to identify which device is available or no longer available.

To keep a particular device a favorite device, its device unique identifier can be retrieved using the Device Manager getDeviceUniqueIdentifierFromDeviceGuid API and it can then be used to set the Device Manager favorite devices as shown below:

async function setThisDeviceAsFavorite(deviceManager, deviceGuid) {
    // first get the unique device ID of the device identified
    // by its GUID, then set this unique device ID as favorite
    // in the device manager to connect only to that device
    let property = new CaptureProperty(
      CapturePropertyIds.UniqueDeviceIdentifier,
      CapturePropertyTypes.String,
      deviceGuid
    );

    const result = await deviceManager.getProperty(property);

    property = new SocketMobile.CaptureProperty(
      SocketMobile.CapturePropertyIds.Favorite,
      SocketMobile.CapturePropertyTypes.String,
      result.value
    );

    return deviceManager.setProperty(property);
}

_onCaptureEvent (event, handle) {
  if(event) {
    print('event: ', event);
    String eventName = getEventName(event.id);
    print(`received ${eventName}`);
    if(event.id === CaptureEventIds.DeviceArrival) {
      print('Open the device: ', event.value.guid);
      Capture deviceCapture = new Capture();
      try {
        dynamic result = await deviceCapture.openDevice(event.value.guid, capture);

        _devices[event.value.guid] = captureDevice;

        result = await setThisDeviceAsFavorite(deviceCapture, event.value.guid);
      } on CaptureException catch (exception){
        print('error while setting device manager favorite: ' + exception.code.toString() + ': ' + exception.message);
      }
    }
  }
  ...

This example sets the device favorite to the first device that connects to the host if the device favorite was set with a *. By doing so, this device becomes the preferred device to be connected to this host, until the favorite device string is reset to either an empty string to stop the auto discovery and connect mode, or to * to connect to another or the same device.

Bluetooth Low Energy Devices Discovery

The Device Manager offers an API to discover the Bluetooth Low Energy devices that are in the vicinity.

Once a device has been discovered, its identifier UUID can be used to set the Device Manager favorite devices. As soon as the Device Manager favorite devices is set with this UUID, the Device Manager will then connect to this particular contactless reader/writer device.

Here is an example showing how to start the device discovery:

CaptureProperty property = new CaptureProperty(
  CapturePropertyIds.StartDiscovery,
  CapturePropertyTypes.Ulong,
  5000
);

dynamic result = await deviceCapture.getProperty(property);

Then for each discovered device the CaptureEventIds.DeviceDiscovered event is fired:

_onCaptureEvent(e, handle) {

    switch (e.id) {
      case CaptureEventIds.DeviceDiscovered:
        print('Discovered the device: ' + event.value));
        const discoveredDevice = jsonDecode(event.value);
        try{

          dynamic result = await setThisDeviceAsFavorite(captureDeviceManager, event.value.guid);

          CaptureProperty property = new CaptureProperty(
            CapturePropertyIds.Favorite,
            CapturePropertyTypes.String,
            discoveredDevice.identifierUUID
          );

          result = await deviceManager.setProperty(property);

        } on CaptureException catch (exception){
          print(exception.code.toString() + ': ' + exception.message);
        }
        break;
    }
  }
  ...

Here is how the event.value might look:

{
  "identifierUUID": "BE495AA0-A93C-4274-9006-F3BC2428ACDF",
  "name": "Socket D600 [7EF619]",
  "serviceUUID": "6CB501B7-96F6-4EEF-ACB1-D7535F153CF0"
}

In this case the last discovered device is set as favorite. The device identifierUUID is what can be used to set the favorite devices with in order to connect to that particular device.

The device discovery ends once the time out has elapsed and notifies the app by firing the SocketMobile.CaptureEventIds.DiscoveryEnd event:

_onCaptureEvent(e, handle) {

    switch (e.id) {
      case CaptureEventIds.DiscoveryEnd:
          print('end of discovery');
        } on CaptureException catch (exception){
          print(exception.code.toString() + ': ' + exception.message);
        }
        break;
      ...
    }
  }

Contactless Reader/Writer Data Format (D600 only)

When the contactless reader/writer reads data from a card, it can display this data in four different formats:

• Tag Type and ID: DataFormat.tagTypeAndId This Data Format will display the type of card (NFC Forum, etc.) as well as the unique identifier associated with the card.

• ID Only: DataFormat.idOnly This Data Format will only display the unique identifier from the card. (This format is not supported)

• Tag Type and Data: DataFormat.tagTypeAndData This Data Format will display the type of card (NFC Forum, etc.) as well as the expected data on the card. This data can be translated into a String format or otherwise if expected.

• Data Only DataFormat.dataOnly This Data Format will display only the data from the card. (This format is not supported.)

Setting and Getting the current Data Format (D600 only)

You can change the current data format by using one of the aforementioned data format types. Example of setting to DataFormat.tagTypeAndData:

CaptureProperty property = new CaptureProperty(
  CapturePropertyIds.DataFormatDevice,
  CapturePropertyTypes.Byte,
  CapturePropertyValues.TagTypeAndData
);

dynamic result = await deviceCapture.setProperty(property);

Getting the current data format is similar to setting:

CaptureProperty property = new CaptureProperty(
  CapturePropertyIds.DataFormatDevice,
  CapturePropertyTypes.None,
  {}
);

dynamic result = await deviceCapture.getProperty(property);