CODEWITHSUNDEEP
androidbluetooth-lowenergyibeacon-androidaltbeacon
jcady
jcady

Reputation: 3968

Using AltBeacon as a Wrapper For BLE Scanning/Connections

My application doesn't use beacons (at least not in the common meaning). The use case is to continuously background scan for BLE peripherals matching a specific format, then connect to those peripherals and transmit/receive data and disconnect (possibly doing this more than once).

The stability and reliability of Bluetooth LE on Android leaves something to be desired, especially if supporting earlier API versions (18+), as I am. AltBeacon seems to be a seasoned library that handles a lot of the weird edge cases and intricacies in Android Bluetooth LE management (at least on the scanning side). I'd like to leverage this library to scan and identify my peripherals and then connect to them on my own. Does anyone know how I might be able to achieve this?

Upvotes: 0

Views: 631

Answers (1)

davidgyoung
davidgyoung

Reputation: 64916

While the Android Beacon Library really is not designed to scan for bluetooth services, there are certain cases where it can be convenient for that purpose. Be forewarned, however, that doing this goes against the grain of its design, and forces you to do a few pretty ugly hacks. If such hacks make your eyes bleed, then read no further! For those who can stand it, here's what you'd need to do:

  • Set up a beacon parser that will look for a GATT Service UUID. You must match on a few bytes in the service UUID, and the library's matchers are only designed to match a few bytes at a time. So if you have a GATT Service UUID of 00010203-0405-0607-0809-0a0b0c0d0e0f, you should take the first three bytes: 00,01,02 and use them as the matching expression. Because the matching expression has a different endianness, you have to reverse the order of the bytes to be 02,01,00. So you end up with code like this:

    BeaconManager beaconManager = org.altbeacon.beacon.BeaconManager.getInstanceForApplication(this);
beaconManager.getBeaconParsers().add(new BeaconParser().
        setBeaconLayout("m:0-2=020100,i:0-15l,p:15-15"));

  • Start ranging based on a region that matches your full GATT Service UUID. (Again, you must replace the UUID with that of your service.):

    Region gattServiceRegion = new Region("gattServiceRegion",
        Identifier.parse("00010203-0405-0607-0809-0a0b0c0d0e0f"), null, null);
beaconManager.setRangeNotifier(this);
beaconManager.startRangingBeaconsInRegion(region);

Now the library will make a callback to your class' didRangeBeaconsInRegion method each time it sees an advertisement for that GATT Service UUID. So you know it is nearby, and you can get all of the power saving, background launching and other benefits of the library. The problem now is that the library doesn't expose any reference to the raw BluetoothDevice object needed to call connectGatt(...).

So unless you modify the library source code you still have to use the raw scanning APIs once you know the beacon is around just to get this reference. You have to decide if using the Library is worth all this trouble, given that you have to use the raw scanning APIs to get the BluetoothDevice to make a connection, anyway.

Upvotes: 2

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