We have an IoT device that has an onboard BLE chip (Anaren A20737A) that the user can control from their mobile phone. At times, the phone will pair with the device (or at least report that it is paired), but will not receive any data, and all commands appear to be ignored by the device. Connecting the logger to the device, we can see that it believes that it is sending out messages correctly, and that it is paired with the phone. The solution appears to be forgetting the BLE pairing from the Bluetooth settings on the phone, and sometimes restarting the phone as well. No changes to the IoT device appear to have any impact, the only thing that works is forgetting the pairing from the phone's settings. This problem has occurred on both iPhone and Android (separate code bases).
EDIT
The problem is seen on iOS 7.0 and multiple versions of android from at least 4.4 onward.
Logging the data out from the chip we see it drop the connection and start advertising. About 1 in 10 times, the phone seems to believe that it has a connection with the device, but the logs on the device show that it is still in advertising mode.
Has anyone else ever seen this issue?
I am creating an APP in which I need to sync the data from pedometer(Bluetooth 4.0). I took reference from Android sample BLE project.
It's working fine with most of the devices but in some model like XIAOMI MI5 and some samsung models like E7 I am facing issue where BluetoothGattCallback functions are not getting called.
Sometimes If I connect pedometer with other APP and then reconnect it with my APP it starts working.
I am unable to find where is the problem.What is the best way to make it work on all supported phones?
You can print some log in method onConnectionStateChange of BluetoothGattCallback so that you can confirm whether your bluetooth connection state is connecting.
I'm developing an Android program that uses Bluetooth.
The first device is Haier W718 Android 4.0.3 , the second one is Samsung GT-P5110 Android 4.2.2. They both listen and may connect each other and transmit some data.
Almost everything works properly but I encountered a strange problem in Haier W718.
If I turn off Bluetooth of my Haier device, when my program is listening (BluetoothServerSocket.accept()), sometimes I can not turn on Bluetooth again. I press the Bluetooth icon in the status bar, but nothing happens.
In case I manage to turn Bluetooth on, BluetoothSocket.connect() gives me the error "IOException Service discovery failed", however BluetoothServerSocket.accept() works good.
In order to solve this problem I have to turn my phone off and on again.
What may be the reason of this strange behavior?
I have only 2 Android devices and Samsung works good. May it be a problem of Haier firmware?
Trying to build connection between Nexus4 and Nexus 5 via Insecure Bluetooth Connection. Insecure meaning no pairing is required.
The code hence developed did work for sometime and both phones were able to talk to each other. An app on nexus4 would launch via broadcast message when Nexus 5 initiates BL Connection.
At some point, i get this
E/BluetoothRemoteDevices: aclStateChangeCallback: Device is NULL
E/bt-btm btm_sec_disconnected - Clearing Pending flag
in Nexus4 phone. Post which, I am not getting any Broadcast message when the other phone(Nexus 5) tries to set up a connection. Any pointers why I am getting this ?
PS : Same is working fine across other phones. I did restart Nexus4, renamed bluetooth name. But dint had the luck.
Try restarting the bluetooth or the entire device. I have noticed this issue on devices with the (a particular one?) Broadcom bluetooth chipset. The Android bluetooth stack just decides to close the connection sometimes before it reaches your app. Sometimes I can detect this by listening for ACL_CONNECTED events, I am hoping to programmatically restart the bluetooth by detecting it this way. It goes away most of the time after the restart.
I am currently developing an application that will use Bluetooth Low Energy (testing on the Nexus 4). After getting started with the official BLE APIs in Android 4.3, I have noticed that after I connect a device for the first time I am rarely able to successfully connect to / communicate with that device or any other device again.
Following the guide here, I can successfully connect to a device, scan services and characteristics, and read/write/receive notifications without any issues. However, after disconnecting and re-connecting, I am often unable to either scan services/characteristics or unable to complete a read/write. I can't find anything in the logs to indicate why this is happening.
Once this happens I have to uninstall the application, disable Bluetooth, and restart the phone before it will start working again.
Whenever a device is disconnected I make sure to call close() on the BluetoothGatt object and set it to null. Any insights?
EDIT:
Log dumps: For these logs I rooted my phone and upped the trace levels of related items in /etc/bluetooth/bt_stack.conf
Successful connection - First attempt after rebooting the phone and installing the app. I am able to connect, discover all services/characteristics, and read/write.
Failed Attempt 1 - This is the next attempt after disconnecting from the successful connection above. It seems I was able to discover characteristics, but the first attempt to read returned a null value and disconnected soon thereafter.
Failed Attempt 2 - An example where I am not even able to discover services/characteristics.
EDIT 2:
The device to which I am trying to connect is based on TI's CC2541 chip. I obtained a TI SensorTag (also based on the CC2541) to play around with and discovered that TI released an android app for the SensorTag yesterday. However, this app has the same problem. I tested this on two other Nexus 4s with the same result: Connection to the SensorTag is successful the first or second time, but (according to the logs) fails to discover services thereafter, causing all sorts of crashes. I'm starting to wonder if it's an issue with this specific chip?
Important implementation hints
(Perhaps some of those hints aren't necessary anymore due to Android OS updates.)
Some devices like Nexus 4 with Android 4.3 take 45+ seconds to connect using an existing gatt instance. Work around: Always close gatt instances on disconnect and create a fresh instance of gatt on each connect.
Don't forget to call android.bluetooth.BluetoothGatt#close()
Start a new thread inside onLeScan(..) and then connect. Reason: BluetoothDevice#connectGatt(Context context, boolean autoConnect, BluetoothGattCallback callback) always fails, if called inside LeScanCallback() {...}.onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord) in the same thread on Samsung Galaxy S3 with Android 4.3 (at least for build JSS15J.I9300XXUGMK6)
Most devices filter advertising
Better not use android.bluetooth.BluetoothAdapter#startLeScan(UUID[] serviceUuids, LeScanCallback callback) with the parameter to filter for certain service UUIDs because this is broken completely in Samsung Galaxy S3 with Android 4.3 and doesn't work for 128bit UUIDs in general.
Gatt always can process one command at a time. If several commands get called short after another, the first one gets cancelled due to the synchronous nature of the gatt implementation.
I often see even on modern devices with Android 5, that Wifi interferes withs bluetooth and vice versa. As a last resort, turn off wifi to stabilize bluetooth.
Tutorial for beginners
A pretty OK entry point for newcomers could be this video tutorial: Developing Bluetooth Smart Applications for Android http://youtu.be/x1y4tEHDwk0
The issue and work around described below is probably fixed now by OS updates
Work around: I could "stabilize" my app doing that...
I provide the user a setting "Restart Bluetooth". If that setting is enabled, I restart Bluetooth at some points that indicate the begin of BLE stack becoming unstable. E.g. if startScan returns false. A good point may also be if serviceDiscovery failes. I just turn Bluetooth off and on.
I provide another setting "Turn off WiFi". If that setting is enabled, my app turns off Wifi when the app is running (and turns it back on afterwards)
This work around is based on follwoing experiences...
Restarting Bluetooth helps to fix problems with BLE in most cases
If you turn off Wifi, the BLE stack gets much more stable. However, it also works fine on most devices with wifi turned on.
If you turn off Wifi, restarting Bluetooth fully recovers the BLE stack without the need to reboot the device in most cases.
Turning WIFI OFF:
I can confirm too, that turning WIFI OFF makes Bluetooth 4.0 more stable especially on Google Nexus (I have a Nexus 7).
The problem
is that the application I am developing needs both WIFI and continous Bluetooth LE scanning. So turning WIFI OFF was no option for me.
Moreover I have realised is that continous Bluetooth LE scanning can actually kill WIFI connection and make the WIFI adapter unable to re-connect to any WIFI network until BLE scan is ON. (I'm not sure about mobile networks and mobile internet).
This definitely happened on the following devices:
Nexus 7
Motorola Moto G
However BLE scanning with WIFI on seemed pretty stable on:
Samsung S4
HTC One
My workaround
I scan BLE for a short period of time 3-4 seconds then I turn scan OFF for 3-4 seconds. Then ON again.
Obviously I always turn BLE scan OFF when I'm connecting to a BLE device.
When I disconnect from a device I restart BLE (turn adapter OFF and then ON) to reset the stack before starting scan again.
I also reset BLE when discovering services or characteristics fails.
When I get advertisement data from a device that the app should connect to (lets say 500 times without being able to connect - thats about 5-10 seconds of advertising) I reset BLE again.
Make sure your Nexus is paired to the device. I can't verify whether or not the communication works properly, but you will be able to connect more than once without a reboot. It seems the first connect is not requiring pairing but all subsequent attempts do.
I will update this answer in a couple of days when I test service discovery and gatt read and write requests without a reboot.
EDIT:
It turns out I was testing on a development firmware version (our sensor) that was causing issues if not paired. Our latest production firmware build works fine on the 2540s and 2541s.
EDIT:
I did notice that on the Nexus 7 2013, connections are more stable when WiFi is turned off. I'd like to know if this helps anyone else.
EDIT:
I seem to have had it backwards with pairing. Everything works fine when not paired. After pairing, I am experiencing the exact same symptoms as the OP. It's just not known yet if this is related to our firmware or the Android BLE API. Be careful if testing this because once paired, you may not be able to unpair due to a bug explained in 3b of this post.
In some models there is a defect:
https://code.google.com/p/android/issues/detail?id=180440
On the other hand in my case the problem was, that my connection was not properly closed in onDestroy method. After correct closing, problem for me is not existing, not matter that wifi is turned on or off.
btGatt.disconnect();
btGatt.close();
I was facing a similar issue. My fix was
if (Build.VERSION.SDK_INT >= 23) {
mBluetoothGatt = device.connectGatt(this, false, mGattCallback, BluetoothDevice.TRANSPORT_LE);
} else {
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
}
& calling close after disconnect.