How to correctly use UUID.fromString method?

Question

I am trying to read/write these ble characteristics:

Right now, I'm trying to read AA01*

I am using this library to do it.

Here's my code:

private void connectToSensorTag(RxBleDevice rxBleDevice) {
    rxBleDevice.establishConnection(getApplicationContext(), false)
            .doOnError(new Action1<Throwable>() {
                @Override
                public void call(Throwable throwable) {
                    int i = 0;
                }
            })
            .flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(UUID.fromString("AA01*")))
            .subscribe(new Subscriber<byte[]>() {
                @Override
                public void onCompleted() {
                    int i = 0;
                }

                @Override
                public void onError(Throwable e) {
                    int i = 0;
                }

                @Override
                public void onNext(byte[] bytes) {
                    int i = 0;
                }
            });

I get this error:

java.lang.IllegalArgumentException: Invalid UUID: AA01*

I also tried the solutions from this similar question but nothing works. Same error.

Answer 1

In the BLE specification there are two kinds of UUIDs.

• Fully qualified 128 bits long which are usually assigned for a specific vendor of the BLE device for non-standard functionality: UUID.fromString("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");

• Also fully qualified (but defined by standard) UUIDs which have the same prefix and postfix: UUID.fromString("F000xxxx-0451-4000-B000-000000000000"); where xxxx is the place to fill the four characters you get from the SensorTag specification. For convenience the standard UUIDs are usually referenced with the four characters identifier.

Additionally if you're dealing with a SensorTag device you can checkout the library demo application that was shown on MCE^3 conference this year:

The talk: https://www.youtube.com/watch?v=0aKfUGCxUDM

The demo application repository: https://github.com/dariuszseweryn/2016_MCE_Demo_RxAndroidBLE

I hope that will help you.

Best Regards.

Answer 2

If you need a faster java.util.UUID.fromString(), you can use Fast-UUID-Parser instead. It returns java.util.UUID and it's 4 times faster than java.util.UUID.fromString().

Answer 3

You must provide a full uuid:

UUID uid = UUID.fromString("f000aa01-0451-4000-b000-000000000000");