First, the source code for the BLE Peripheral Simulator is a tremendous resource for anyone investigating Web Bluetooth.
There is a an approved list of GATT Services.
When I modified the Android source code to use a custom defined GATT service (easy to do by simply specifying your own UUID in the Android code) pairing from the web page to the Android app running the GATT sever fails.
The Web Bluetooth documentation does state, "If device’s advertised Service UUIDs have a non-empty intersection with the set of Service UUIDs, add device to result and abort these sub-steps [for pairing]."
Does this mean only services in the approved GATT list are supported? If so, what is the rational? It seems that such a restriction would limit innovation.
I am working with web-bluetooth also and i was able to talk with custom services, yet to read data from them you have to have device docs explaining how to talk to that services. I think this approved list is like generally used list which doesn't require unique logic to get data. However there is difference since some characteristics are blacklisted for web-bluetooth yet available to fetch data from using ios/android stuff.
If I had done some more research on Stack Overflow I would have realized the UUID spec requires lowercase a-f.
Type of Character generated by UUID
The following values work for a custom defined service and characteristic:
private static final UUID SERVICE_UUID = UUID.fromString("29143321-ef6c-4761-947c-c858f9a2e8f1");
private static final UUID CHARACTERISTIC_UUID = UUID.fromString("92f3131b-ffa8-4dd1-a12b-641d65a78857");
Related
For weeks I was struggling to create an app that connected to an arduino device over Bluetooth Low Energy (Bluetooth LE) and I finally got it working today. I am sharing the resources I found so that if someone else is struggling they can learn from my experience. The information I am sharing is for bluetooth LE only. If your device is using bluetooth classic this will not work as they are not compatible.
For anyone who is new to this here is some terms you will need to know. You need to use them in your program to communicate with bluetooth LE.
UART: universal asynchronous receiver-transmitter. This is the protocol that is used to send data to a device via bluetooth LE and to receive data.
GATT: Generic Attribute Profile. This defines how data will be transferred back and forth using Services and Characteristics.
This was an excellent tutorial on how to create the app:
https://www.jenx.si/2020/08/13/bluetooth-low-energy-uart-service-with-xamarin-forms/
This app will scan for BLE devices, connect to them, send data to the device, and receive data from the device. My app is for android, but it looks like the app from this tutorial will work for IOS as well.
Once I created the app I searched for the UART UUID's of my device (an Adafruit Feather Bluefruit LE). Here is the page where I found the codes for my device:
https://learn.adafruit.com/adafruit-feather-m0-bluefruit-le/uart-service
I found the Send and Receive UUID's from the Nordic Semiconductor website:
https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v14.0.0%2Fble_sdk_app_nus_eval.html
Then in the GattIdentifiers page I replaced the generic UUID's that were entered with the UUID's for my device. Here is what my GattIdentifiers page looks like with my UUID's.
public class GattIdentifiers
{
public static Guid UartGattServiceId = Guid.Parse("6E400001-B5A3-F393-E0A9-E50E24DCCA9E");
public static Guid UartGattCharacteristicReceiveId = Guid.Parse("6E400003-B5A3-F393-E0A9-E50E24DCCA9E");
public static Guid UartGattCharacteristicSendId = Guid.Parse("6E400002-B5A3-F393-E0A9-E50E24DCCA9E");
public static Guid SpecialNotificationDescriptorId = Guid.Parse("00002902-0000-1000-8000-00805f9b34fb");
}
A note on this is to make sure you put the right UUID's with the send and receive characteristics defined in the file. I had them reversed at first which was giving me "null" results. So if they are not working try reversing them.
I hope this helps!
I'm developing a frame exchange sequence between an nRF52840 and an Android smartphone using the BLE protocol.
The service exposed by nRF52840 has the following 16-bit UUID : EB7A
In my Android application, if I only want to retrieve BLE devices that have this service, I need to initialize the filter like this :
private var scanFilters: List<ScanFilter> = arrayListOf(
ScanFilter.Builder().setServiceUuid(ParcelUuid(UUID.fromString("0000eb7a-0000-1000-8000-00805f9b34fb"))
)
However, if I want to write about a feature of this service, I have to use the following UUID:
0000eb7a-0000-0000-0000-000000000000
I don't understand why I can't use the same UUID for filtering as for read/write operations, can you help me?
I don't know whether you have figured it out. If yes, would be interesting to know what you have discovered. I am quite new to android and nRF dev myself, but I have 2 theories for your question:
If you are using a vendor-specific UUID for the filter, I guess you are not able to modify it, which is why you have to use a different UUID.
Have you tried deriving the UUID as a String for example and then using it in a filter (not sure if this would work thou)
public static String SOME_SERVICE = "0000eb7a-0000-1000-8000-00805f9b34fb"
ScanFilter = newScanFilter.Builder().setServiceUuid(UUID.fromString(SOME_SERVICE);
I use CoreBluetooth to connect my iPhone with a device equipped with Bluetooth 4.0.
I print its (as a peripheral) UUID :
<CBPeripheral: 0x1742fca80, identifier = B148AD69-1FC7-498C-016F-33BA3BE041A3, name = HMSoft, state = disconnected>
I wonder whether this identifier is an inherent attribute of a device.
Since I use the following code in android to get its UUID which is different from what I get using CoreBluetooth in iPhone:
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
for (ParcelUuid uuid : device.getUuids()) {
Log.d("UUID", uuid.getUuid().toString());
}
( I connect with the same device but the print UUID is different).
Identifier in CBPeripheral is a randomly generated Unique identifier. This gets varied over time. In case of a CBPeripheral, we need to know about two kinds of UUIDs. One is ServiceUUID and other is CharacteristicUUID. Each peripheral broadcast data over each service. A single service can have more than one characteristics. For eg. a device information service can have device name, device version etc as its characteristics.
See the following image for a better understanding CBPeripheral. The Apple docs speaks well on this.
My first answer, so I hope I won't make a fool of myself ;-)
BluetoothDevice.getUuids():
Returns the supported features (UUIDs) of the remote device. I.e. UUIDs of services advertised by the device, not UUID of the device itself.
I'm currently looking myself for an Android way to get the UUID of a discovered BLE device...
The Android Bluetooth API allows you to register an SDP service using:
String BLUETOOTH_NAME="MyBluetoothService";
mAdapter.listenUsingRfcommWithServiceRecord(BLUETOOTH_NAME, UUID.fromString(uuid));
It also allows you to initiate a Service Discovey on a remote Bluetooth Device to find the list of active service UUID's:
device.fetchUuidsWithSdp();
However, there doesn't seem to be any public method available to get the service name. Can it be acquired by other means?
I suppose you want to get the names of services running on the device as you would do on a linux box with
sdptool browse local | egrep "Service Name:"
So the answer is no, as there is no Android API method and sdptool is not on android.
However you might write a c library containing an according function using the NDK and call the function via JNI (see Bluetooth for Programmers for the first on http://people.csail.mit.edu/rudolph/Teaching/Articles/BTBook.pdf).
By the way: Why do you want to list the services by name and not by UUID. It is my experience that service names slightly differ with implementations while UUIDS are credible.
I'm starting to work on Bluetooth in Android recently.
I want to build an application that can read the data recorded by a sensor through bluetooth.
I have some sample code, but looks like I need another UUID of a different device.It looks like this:
private static final UUID MY_UUID = UUID
.fromString("00001101-0000-1000-8000-00805F9B34FB");
Later on in the code, it uses this UUID to make a connection:
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
I have done some research online, like [here][1]. I think I need a different UUID number for the new device I'm working on. How do I get the UUID number?
On the device, there are two lines of number saying:
SN: 1201L0023
BT: 10:00:E8:C5:16:85
Thanks in advance!
Jake
UUIDs are not tied to particular devices. They identify software services. Some UUIDs for defined profiles are set by BT. The UUIDs used with RFCOMM sockets like your example are arbitrary. You just need both sides to use the same one. In general, devices connect and then use service discovery protocol to find out what services (UUIDs) are supported on the remote device.