startLeScan with 128 bit UUIDs doesn't work on native Android BLE implementation

Question

I am having trouble using startLeScan( new UUID[]{ MY_DESIRED_128_BIT_SERVICE_UUID }, callback ) on the new introduced BLE API of Android 4.3 on my Nexus 4.

The callback just doesn't get called. I still can see incoming packages in the log:

08-02 15:48:57.985: I/bt-hci(1051): btu_ble_process_adv_pkt
08-02 15:48:58.636: I/bt-hci(1051): BLE HCI(id=62) event = 0x02)

If I don't use the parameter to filter for UUIDs it works. We are using a manufacturer specific 128bit UUID for device of our company.

Now, our device offers more services than I am providing in the array. But that shouldn't be the problem.

Is anyone facing the same problem? Any solutions?

Edit

There are several problems related to scanning, this question only discusses one: If you also have some issue with scanning, read this comment first. Also keep in mind, that my device imposes a 16bit and a 128bit UUID. Most of you guys use 16bit UUIDs provided by the BLE standard like Heart rate or Speed and Cadence.

Answer 1

@Navin's code is good, but it includes an overflow bug from the original 16-bit Android code. (If either byte is larger than 127 then it becomes a negative integer.)

Here's an implementation which fixes that bug and adds 128-bit support:

private List<UUID> parseUuids(byte[] advertisedData) {
     List<UUID> uuids = new ArrayList<UUID>();

     ByteBuffer buffer = ByteBuffer.wrap(advertisedData).order(ByteOrder.LITTLE_ENDIAN);
     while (buffer.remaining() > 2) {
         byte length = buffer.get();
         if (length == 0) break;

         byte type = buffer.get();
         switch (type) {
             case 0x02: // Partial list of 16-bit UUIDs
             case 0x03: // Complete list of 16-bit UUIDs
                 while (length >= 2) {
                     uuids.add(UUID.fromString(String.format(
                             "%08x-0000-1000-8000-00805f9b34fb", buffer.getShort())));
                     length -= 2;
                 }
                 break;

             case 0x06: // Partial list of 128-bit UUIDs
             case 0x07: // Complete list of 128-bit UUIDs
                 while (length >= 16) {
                     long lsb = buffer.getLong();
                     long msb = buffer.getLong();
                     uuids.add(new UUID(msb, lsb));
                     length -= 16;
                 }
                 break;

             default:
                 buffer.position(buffer.position() + length - 1);
                 break;
         }
     }

     return uuids;
 }

Answer 2

Try this to retrieve/filter the device from the advertised 128-bit UUIDs:

private List<UUID> parseUUIDs(final byte[] advertisedData) {
    List<UUID> uuids = new ArrayList<UUID>();

    int offset = 0;
    while (offset < (advertisedData.length - 2)) {
        int len = advertisedData[offset++];
        if (len == 0)
            break;

        int type = advertisedData[offset++];
        switch (type) {
        case 0x02: // Partial list of 16-bit UUIDs
        case 0x03: // Complete list of 16-bit UUIDs
            while (len > 1) {
                int uuid16 = advertisedData[offset++];
                uuid16 += (advertisedData[offset++] << 8);
                len -= 2;
                uuids.add(UUID.fromString(String.format(
                        "%08x-0000-1000-8000-00805f9b34fb", uuid16)));
            }
            break;
        case 0x06:// Partial list of 128-bit UUIDs
        case 0x07:// Complete list of 128-bit UUIDs
            // Loop through the advertised 128-bit UUID's.
            while (len >= 16) {
                try {
                    // Wrap the advertised bits and order them.
                    ByteBuffer buffer = ByteBuffer.wrap(advertisedData,
                            offset++, 16).order(ByteOrder.LITTLE_ENDIAN);
                    long mostSignificantBit = buffer.getLong();
                    long leastSignificantBit = buffer.getLong();
                    uuids.add(new UUID(leastSignificantBit,
                            mostSignificantBit));
                } catch (IndexOutOfBoundsException e) {
                    // Defensive programming.
                    Log.e(LOG_TAG, e.toString());
                    continue;
                } finally {
                    // Move the offset to read the next uuid.
                    offset += 15;
                    len -= 16;
                }
            }
            break;
        default:
            offset += (len - 1);
            break;
        }
    }

    return uuids;
}

Answer 3

This is a reported bug at least in Android 4.3 JWR66Y:

• Filtering works, if I provide my 16bit UUID
• Filtering doesn't return any scan results, if I provide my 128bit UUID or if I provide both UUIDs

My setting: My device offers 2 UUIDs on advertising (1 16bit and 1 128bit) and 4 UUIDs on service discovery (1 128bit and 3 16bit).

Even if it gets fixed, I warn everybody against using the filter option provided by Android. For backward compatibility and since it's broken on Samsung Galaxy S3 with Android 4.3