Whiz Whiz - 4 months ago 41
Android Question

How to correctly use UUID.fromString method?

I am trying to read/write these ble characteristics:

enter image description here

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

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.

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