I've been developing an app for Android who communicates with a physical piece of hardware via bluetooth. Until now we've been using normal bluetooth, but this has now changed to BLE. I am not an android developer, why this is a bit difficult for me.
At the moment I am just running a proof of concept. Whenever the physical device receives something, it transmits it back, and I can confirm this using proper BLE terminal apps. I've identified the characteristics I need to use, and I can connect to the device and send data to it. Though I cannot receive data, I am never receiving anything back.
The code shown below shows what I'm currently doing, trying to send (successfully) to the device and not so successfully receiving data. Am I totally misunderstand this concept?
Hope someone can give me a hand.
#Override
public void onConnectionStateChange(BluetoothGatt
gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
Log.i("GattCallback", "connected");
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
Log.i("GattCallback", "Disconnected");
break;
default:
System.out.println(newState);
}
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
byte[] newValue = characteristic.getValue();
System.out.println("RECEIVED: " + Arrays.toString(newValue));
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
for (BluetoothGattService gattService : gatt.getServices()) {
Log.i("derp", "onServicesDiscovered: service=" + gattService.getUuid());
for (BluetoothGattCharacteristic characteristic : gattService.getCharacteristics()) {
Log.i("derp", "onServicesDiscovered: characteristic=" + characteristic.getUuid());
if(characteristic.getUuid().toString().contains("9616")){
System.out.println("We have found the read characteristic.");
gatt.setCharacteristicNotification(characteristic, true);
BluetoothGattDescriptor desc = characteristic.getDescriptor(UUID.fromString("49535343-1e4d-4bd9-ba61-23c647249616"));
if(desc == null){
System.out.println("NULL!");
return;
}
desc.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
gatt.writeDescriptor(desc);
System.out.println("Should be subscribed.");
}
else if(characteristic.getUuid().toString().contains("9bb3")){
System.out.println("Send characteristic found");
characteristic.setValue("Test\n\r");
boolean res = gatt.writeCharacteristic(characteristic);
if(res)
System.out.println("Success");
break;
}
}
}
}
}
Related
I am developing an application that connects through Bluetooth Low Energy to a Bluetooth scale and read weight.
The scale is Hi Weigh CF 150.
I have followed this tutorial
https://punchthrough.com/android-ble-guide/
I am connecting to to the scale and I come to the point where I try to discover the services of the scale.
class GattCallBack extends BluetoothGattCallback {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
String deviceAddress = gatt.getDevice().getAddress();
if ( status == BluetoothGatt.GATT_SUCCESS) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
Log.w(TAG, "Scale Connected successfully.");
bluetoothGatt = gatt;
Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
#Override
public void run() {
if (bluetoothGatt != null) {
bluetoothGatt.discoverServices();
}
}
});
//#TODO Store a reference to BluetoothGatt
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
Log.i(TAG, "Succesfully disconected from Service $deviceAddress");
gatt.close();
} else {
Log.i(TAG, "Error $status encountered for #deviceAAddress! Disconnecting");
gatt.close();
}
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
Log.w(TAG, " Devices service " + gatt.getDevice().getName() + ": " + gatt.getServices().size());
Iterator<BluetoothGattService> iter = gatt.getServices().iterator();
while (iter.hasNext()) {
Log.w(TAG, "Found service: " + iter.next().getUuid());
}
}
}
At this point the onServicesDiscovered(BluetoothGatt gatt, int status) callback always has zero discovered services with status 129.
Status 129 is a generic error from what I have understand and I have no other info about it.
By scanning the same scale with Nordic semiconstructor nrfConnect app, the services of the scale are discovered as you can see at the screenshot.
From the Nordic's app I can see that the service is "49535343-fe7d-4ae5-8fa9-9fafd205e455" and the characteristic for the weight is "49535343-1e4d-4bd9-ba61-23c647249616"
Is it possible that I have to use password to read the services (I a have given a password but I don't know how to use it).
Any help is appreciated.
After connect connectGatt and readCharacteristic BluetoothGatt disconnects and onConnectionStateChange calls on ASUS device. On sony xperia z2 disconnect doesn't happen. I spent a lot of time ... Does anyone have any ideas ?
connect
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
mBluetoothGatt = mDevice.connectGatt(ActivityExamination.this, true, mCallback2 , BluetoothDevice.TRANSPORT_LE);
} else {
mBluetoothGatt = mDevice.connectGatt(ActivityExamination.this, true, mCallback2 );
}
and listener
BluetoothGattCallback mCallback2 = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
Log.e("onConnectionStateChange", "STATUS: " + status + " STATE: " + newState);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
Log.i("gattCallback", "STATE_CONNECTED");
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
//status is 8
Log.e("gattCallback", "STATE_DISCONNECTED");
Log.i("gattCallback", "reconnecting...");
gatt.connect();
break;
default:
Log.e("gattCallback", "STATE_OTHER");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
Log.e("onServicesDiscovered", "STATUS: " + status);
BluetoothGattService mainService = mBluetoothGatt.getService(UUID_SERVICE_MAIN);
BluetoothGattService deviceInfoService = mBluetoothGatt.getService(UUID_SERVICE_DEVICE_INFO);
BluetoothGattCharacteristic mainCharacteristic = mainService.getCharacteristic(UUID_MAIN_DATA);
BluetoothGattCharacteristic modelCharacteristic = deviceInfoService.getCharacteristic(UUID_DEVICE_MODEL);
mBluetoothGatt.readCharacteristic(modelCharacteristic);
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicRead(gatt, characteristic, status);
Log.e("onCharacteristicRead", "STATUS: " + status + " CHAR: " + characteristic.toString());
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
Log.e("onCharacteristicChanged", "DESCRIPTOR: ");
}
#Override
public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
super.onDescriptorWrite(gatt, descriptor, status);
Log.e("onDescriptorWrite", "DESCRIPTOR: " + descriptor.toString());
}
};
I've run into similar issues in the past, and most of the time it was related to doing to much work in the actual callback method, which is generally called on a Binder thread if I'm remembering correctly.
Have you tried following a pattern similar to the Android tutorials? When receiving events from the bluetooth stack, they send broadcast events to notify of updates. This changes the thread context to the main thread, which would negate any potential of blocking the binder thread -- which may solve your issue.
Generally I set up a Service to handle my Bluetooth LE communication, and create 2 Handlers, one of the main thread and one a background thread. The background thread handler is used for parsing events, and the other for initiating communication with the remote BLE device i.e. connection calls, write, read, etc. This helps take the guess work out of which thread you're calling what on.
Hopefully this helps.
I'm writing printing data to the BluetoothGattCharacteristic of a Zebra ZD410 printer. I do this by chunking the data into 20 byte chunks and writing a chunk at a time with the following code:
mCharacteristic.setValue(bytes);
boolean status = mGatt.writeCharacteristic(mCharacteristic);
and then waiting until I receive BluetoothGattCallback.onCharacteristicWrite() before initiating the writing of the next chunk. This works fine.
If I disconnect() and close() the BluetoothGatt and later connect to the same device again with BluetoothDevice.connectGatt() and then try to write to the Characteristic after onServicesDiscovered() has been called is done and I have my Characteristic again, writing will fail. What I mean by this is that when I write to the Characteristic now, onCharacteristicWrite() will be called with a Characteristic who's getValue() returns the value of the last write on the old Gatt.
After trying to solve this for two days and reading tons of SO posts I haven't found a solution.
How can I fix this?
EDIT
Here is the code for the BluetoothGattCallback
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback()
{
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState)
{
FALog.i(TAG, "onConnectionStateChange Status: " + status);
switch (newState)
{
case BluetoothProfile.STATE_CONNECTED:
FALog.i(TAG, "gattCallback STATE_CONNECTED");
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
disconnectAndCloseGatt();
mCharacteristic = null;
connectionFailed();
FALog.e(TAG, "gattCallback STATE_DISCONNECTED");
break;
default:
FALog.e(TAG, "gattCallback STATE_OTHER");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status)
{
BluetoothGattService service = gatt.getService(PRINTER_SERVICE_UUID);
if (service != null)
{
BluetoothGattCharacteristic characteristic = service.getCharacteristic
(PRINTER_SERVICE_CHARACTERISTIC_UUID);
if (characteristic != null)
{
mCharacteristic = characteristic;
mInternalState = STATE_CONNECTED;
mState = State.CONNECTED;
notifyStateChanged();
print("~JA");
FALog.d(TAG, "Printer connected");
mBluetoothActivity.runOnUiThread(new Runnable()
{
#Override
public void run()
{
mListener.onPrinterConnected();
}
});
}
}
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status)
{
FALog.d(TAG, "received onCharacteristicWrite " + new String(characteristic.getValue()) + "; success: " +
(status == BluetoothGatt.GATT_SUCCESS));
if (status == BluetoothGatt.GATT_SUCCESS)
{
handler.removeCallbacks(writeRunnable);
popQueueAndReleaseLock();
}
}
};
Try writeCharacteristic after the onDescriptorWrite() callback instead of onServicesDiscovered() callback. writeDescriptor holds the mDeviceBusy.
Im am trying to discover the services of my ble device. When I use a LG l3 my code works fine ( I see the uuid I'm looking for). When I try a Samsung s4 I get different service uuids. Why am i getting different uuids ?
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
if (gatt != null) {
mGatt.discoverServices();
}
break;
case BluetoothProfile.STATE_DISCONNECTED:
break;
default:
}
}
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
List<BluetoothGattService> services = gatt.getServices();
for (BluetoothGattService service : services) {
Log.d("DEBUG", "Found service uuid:" + service.getUuid());
/// not getting the UUID im looking for
}
}
}
I'm working on a Android project which is to connect Nexus 7 and a bio sensor through BLE link. The problem is that, I can successfully detect and get list of services and characteristics of the sensor. When I write some data to the specific characteristic, onCharacteristicWrite is automatically called and showed me writing operation is successful. However, the sensor never receive anything from the tablet. And if I use similar app on iPhone, everything works fine. So there's no problem with the device.
Does anyone have any idea of the problem?
Here is my code for write:
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
mConnected = true;
Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
mConnected = false;
Log.i(TAG, "Disconnected from GATT server.");
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
//Once detected services, write to characteristic for 6 times.
int count =6;
while(count>0){
writeCharacteristic();
count--;
}
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic,
int status){
if (status == BluetoothGatt.GATT_SUCCESS){
Log.d(TAG,"Write to Characteristic Success! !");
}
}
};
public boolean writeCharacteristic(){
//check mBluetoothGatt is available
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return false;
}
BluetoothGattService Service = mBluetoothGatt.getService(UUID_MY_SERVICE);
if (Service == null) {
Log.e(TAG, "service not found!");
return false;
}
BluetoothGattCharacteristic characteristic = Service
.getCharacteristic(UUID_MY_CHARACTERISTIC);
if (characteristic == null) {
Log.e(TAG, "char not found!");
return false;
}
byte[] value = {(byte)300,(byte)100,(byte)100};
characteristic.setValue(value);
boolean status = mBluetoothGatt.writeCharacteristic(characteristic);
return status;
}
The output shows "Write to Characteristic Success! !" for six times, thus the writing operation succeeded. However, the device shows that nothing been received from tablet. I also tried to write one byte at a time, or add a timer to let the tablet write to sensor every 2 seconds. But none of them worked. Any ideas?
(Answered by question edit. Converted to a community wiki answer. See What is the appropriate action when the answer to a question is added to the question itself? )
The OP wrote:
Follow Up:
The problem solved by manually pairing the tablet with the device first in the setting instead of pairing by code.
So only using the code snippet of connecting Gatt provided by Android is not good enough to pair the device. I should add another code I found online to pair the devices if I don't want to pair them manually every time:
private void pairDevice(BluetoothDevice device) {
try {
Log.d("pairDevice()", "Start Pairing...");
Method m = device.getClass()
.getMethod("createBond", (Class[]) null);
m.invoke(device, (Object[]) null);
Log.d("pairDevice()", "Pairing finished.");
} catch (Exception e) {
Log.e("pairDevice()", e.getMessage());
}
}