I would like to ask for your valuable opinion about the following:
I'm developing an Android app that needs to connect with the BLE device (whose name I know) automatically on starting the app. Furthermore, the app should be able to keep the phone connected to the BLE device (there will be no "connect" and "disconnect" buttons on the app screen). In other words, if established connection is lost for some reason, the app should be capable to detect this and to re-connect again. The user of the app don't need to be aware of this background process. For him/her, it is only important that the phone is connected with the BLE device.
Simply speaking, I know the name of the BLE device (it is called 'HMSoft'). How should I keep the app connected with this BLE module? Should I use some Thread that will do the job for me in parallel with my other activities within the app MainActivity? Or there is some better approach? Did you have similar experience in the past?
Thank you very much for your time and effort. I really appreciate it.
Sincerely,
Bojan.
You will want to wrap the BLE implementation up in a Service. Within that Service, you will have to implement the logic to connect to the BLE device and keep trying to connect to that BLE device if it becomes unavailable.
Related
We want Android to automatically connect to our custom made BLE peripheral.
Our peripheral should regularly (but infrequently) advertise and attempt to Indicate some time-sensitive sensor data to the phone. Thus we want the phone to be ready to connect at any time.
Generally, you can pair a smart watch with an Android, and Android will then automatically connect to the smart watch whenever it is in range. So we believe our use case should be feasible.
I read a lot of answers that advise to set the "autoconnect" parameter to true when connecting. I have tried that and the reconnections don't persist through a reboot or even after disabling and re-enabling Bluetooth on Android. This answer by Brian says I should scan in the background, but Android made this unrealistic. If I use a foreground service, my users will hate the app. If I use a background service, I may miss the peripheral's attempts to connect during Android's Doze and the code becomes error prone.
Ideally, I want to do something like what Emil said in his answer here. Please read the follow up question and response.
However, we can't see our app through Android's Bluetooth settings. We can only connect to the peripheral and pair with it using our app (or nrf Connect). In desperation, I tried modifying the peripheral's advertising flags. Then I could see it in Android's Bluetooth settings. But when I try to pair using Android's settings, the attempt fails because the peripheral is not in "pairing mode".
We are building both the app and the peripheral, so we can change both. I want to know if our use case is possible and what we need to do to get it working. We are using the STM32WB for our peripheral.
Use a combination of these techniques:
Bond the device. This might be needed due to the crappy Android Bluetooth LE API design that doesn't take the "address type" as an extra parameter when connecting to a device. When you connect using the Bluetooth device address, it looks up a device with this address in the bonding info, and uses the corresponding address type (random or public).
Use connectGatt with autoConnect set to true. This means no timeout, as well as auto-reconnect if the connection drops. Even if it takes days or weeks until the peripheral starts advertising, it will still work.
Listen to https://developer.android.com/reference/android/bluetooth/BluetoothAdapter#ACTION_STATE_CHANGED and restart your connections when Bluetooth is re-started.
Use a Foreground Service in your application's process to prevent the OS from killing the process. Users can nowadays hide the annoying notification in Android settings if they want to.
Listen to https://developer.android.com/reference/android/content/Intent#ACTION_BOOT_COMPLETED to start your app after boot, including your Foreground Service.
Listen to https://developer.android.com/reference/android/content/Intent#ACTION_PACKAGE_REPLACED to automatically restart your app after an app update. See https://stackoverflow.com/a/2134443/556495 for some instructions.
The best approach is to make sure your peripheral can be bonded. Once you have bonded with it you can ALWAYS use autoconnect because Android stores info about bonded devices and you don't have to scan for it anymore. Hence you avoid the issues with scanning in the background.
Although that resolves the need for scanning, you still need to deal with your app being killed once it is in the background. Using a Foreground Service is still the best solution to my knowledge. I don't think you users will hate your app for it...
I need to estabilish a brief communication between a BLE master and a BLE peripherical device.
Until I have to use the mobile phone I have no problems, since I select the bluetooth device from Android, I can connect to it and then I can receive data simply writing them to HM-10.
BUT, this approach is battery expensive, since the BLE scanning is more battery expensive than the BLE advertising (right?). So I want that the mobile becames an advertisor and the HM-10 takes the ROLE of Slave.
BUT, I still don't understand if it is possible to connect to other devices: I tried AT+CONN and it always fails (AT+CONF). Is there any way to send brief data from the HM-10 to the advertisor, even without connecting?
Even my firmware looks slightly different from the readme! For example,AT+LN is present in the documentation but it appears to not exist. Does a better version of the firmware for this device exist, or, are sources available somewhere? I installed the HM-Soft V705 (lastest).
Thanks
UPDATE 1:
#ChrisStratton Ok, I have some intresting news: I was already following your idea (phone advertise sometimes, while HM-10 always scan and tries to connect to the service if it sees it, then HM-10 send some data, phone answer). I managed to make the phone visible from HM-10 (don't ask me how!). I am using the BLE Tool Android app to test everything. Now, the central problem now is that HM-10 won't connect to the android service even if the advertisor is connectable (see attached images).
I am sospicious that the AT+CO (that I discovered is a kind a replacement of AT+LN, but I am not sure) can help, but i don't know how.
I am writing an android app to connect with BLE heart rate monitor devices.
All works well until another application tries to connect to the same service on the BLE device.
Only one application seems to be able to connect at a time.
Is it possible to connect the same BLE service to multple apps at once?
I set up my Bluetooth service in accordance with Link :
You can use BluetoothManager.getConnectedDevices() to get a list of Bluetooth devices, even ones not connected by your app. Unfortunately, you don't also get the service information for those devices.
What you can do then, is connect to the ones not already connected by your app and perform service discovery on them (BluetoothDevice.connectGatt() / BluetoothGatt.discoverServices()), then disconnect those that you aren't interested in. It's a bit cumbersome, but it seems to work for us.
No you can not do that, this is something is not supported in BLE.
I'd like to use android's bluetooth for some kind of sensing devices. But I don't want to connect to these devices. As far as I know Devices won't react to scanning when their own bluetooth is disabled. But is there any way to get my app noticed when such a scan has been performed by a remote device, even when my app is running with bluetooth turned off?
I don't want to force toggling bluetooth on, but I need to get some kind of Action started in other devices running the same app. So I'm wondering if some there is any description/data field that can be sent with a bluetooth scan, so if scan is rejected the app has the opportunity to read that data just to know there was this specific call?
I need to leverage context-awareness within my system as to users, not knowing each other, still can interchange content (if they agree). But I need to find some ways of sensing while I also don't want to have all sensors activated all the time.
Hope you can give me a hint, or tell me that this is simply not possible, which would also help me not spending any more time on that.
Thanks.
I am no Bluetooth specialist and wondering what possibilities are available to find already paired Bluetooth devices automatically when they are range of each other.
Background:
In our case an Android application needs to connect to a dedicated accessory via Bluetooth (Rfcomm). Both devices are known to each other (they are paired). The Android application registers a broadcast receiver. During the startup of the application, the app initiates a discovery to find the dedicated accessory. If the accessory is in range everything works great.
Problem:
The user starts the application outside the range of the dedicated accessory. The Android application tries to discover the accessory without success. Then the user goes into the range of the Bluetooth accessory. The broadcast receiver won’t get notified about the accessory that is in range now.
Similar Thread / Possible Solutions
Similar questions were already asked on stackoverflow (e.g. autoconnect to bluetooth device when in range).
But continuously trying to discover Bluetooth devices in range isn't what I am looking for because this would cause too much battery drain of the Android device.
Another solution would be to try to connect to the paired device in the onResume method of the Activity. This would work but has the disadvantage that the application can’t run in the background. So the user had to bring the application at least once to the foreground to initiate the connection.
A third idea I thought about is to implement a server socket into the Android application too. When the android application is started and the discovery finished without success, the Android application could create server socket and to listen to incoming notifications of the accessory. This would help in some scenarios (e.g. the user starts his application, approaches the accessory, activates the accessory and the accessory notifies the application on startup that it is in range now). But this is still no 100% solution because both devices can start outside the range of each other. Also it would be mandatory to implement additional functionality (Bluetooth server socket in the Android device…).
So I am wondering if better solutions exist. I am looking for a solution where no additional ServerSockets are required and I always get the notification that the two already paired devices are in range of each other :-)
Thanks for any help!
After connecting the device for the first time, keep the mac address in a local list.
On disconnect, use connectGatt with autoconnect set to true to automatically re-connect when you are in range.
Not a full solution, but maybe it's sufficient for your app to poll the accesory's presence whenever the screen is turned on? In that case, this may be helpful: Start Activity on wake up/sleep in Android