I have a Bluetooth LE Joystick with a couple of buttons. I want to connect it directly to the app without using the Bluetooth Settings, but by connecting to it via BluetoothLeScanner.
I already can connect to a Heart Rate Monitor and get periodic notifications of the HR-values.
I also have created a little temperature/light/humidity sensor with an ESP32 to which I can also connnect and display the sensor values in the app.
My understanding of this HID device may be erroneous. With the help of the App BLE Scanner I can connect to this gadget via BLE and see the offered services.
One of them is 0x1812 HUMAN INTERFACE DEVICE, which contains a couple of characteristics of type REPORT, among others which are described HID OVER GATT PROFILE SPECIFICATION (HOGP_SPEC)
How can I find out which button got pressed, what position the joystick has been moved to? I guess that this has to occur via notifications to which I have to subscribe to.
Is there any Android library avaliable to handle HID input devices? What I do NOT want to do is to use the Bluetooth settings and connect to the device and have it become detected as a HID device and replace the keyboard with some odd mapping. I don't want the OS to get involved at all, just like when I connect and use the HRM and the ESP32.
I couldn't find any information on this.
I can connect to the device with my app, enumerate the services and characteristics. But from there on, I have no clue how to work with HID. Ideally I'd get notifications like "Button A has been pressed" "Joystick got moved to x=32" where x would range from -127 to 127, for example.
Accessing the HID characteristics requires the BLUETOOTH_PRIVILEGED permission since Android 5.0. The only way for an app to obtain that permission is to be signed with the same certificates as system apps.
This is a security feature, to prevent an app from receiving HID events from your keyboard and stealing your passwords.
Quoting from https://devzone.nordicsemi.com/cfs-file/__key/communityserver-discussions-components-files/4/BLE_5F00_on_5F00_Android_5F00_v1.0.1.pdf
4.6 Protected services
Android does not allow to read or write data to the following characteristics (and their descriptors):
HID Service (since Android 5):
a. HID Information
b. Report Map
c. HID Control Point
d. Report
FIDO (https://fidoalliance.org/) (since Android 6)
a. U2F (0000FFFD-0000-1000-8000-00805F9B34FB)
Only applications with BLUETOOTH_PRIVILEGED, that is, applications signed
with the same certificate as the system, are able to read and write
data to those characteristics.
Related
Currently, I am developing an app which is communicating with one BLE Hardware which is receiving commands and responding back the command response. To Simulate hardware, We have developed one iOS Simulator app, which is working in Peripheral and responding back on requested command. But Somehow, As and when I try to write to the write characteristics, I got the status = BluetoothGatt .GATT_REQUEST_NOT_SUPPORTED in the onCharacteristicWrite callback. But somehow, I came to know that we need to implement the Central and Peripheral roles into Android app.
But I am still not sure, Do we need to implement Peripheral role as well to send and receive data in multiple packets.
I am developing the app using following nice blog post:
- https://medium.com/#avigezerit/bluetooth-low-energy-on-android-22bc7310387a
- https://android.jlelse.eu/android-bluetooth-low-energy-communication-simplified-d4fc67d3d26e
- https://www.bignerdranch.com/blog/bluetooth-low-energy-on-android-part-2/
And using following repo as learning point of view:
- https://github.com/bignerdranch/android-bluetooth-testbed/tree/a/android-ble-part-3
Thanks in advance!
Typically your phone app is the central and it communicates with a peripheral device over Bluetooth. If you want to send data to the peripheral, you can write a characteristic in the phone app, given writing is enabled for that characteristic. Your central can get data from the peripheral in 2 ways: it can either read a characteristic (if it's enabled) from the peripheral or receive notifications from the peripheral (if it's enabled). So if all you have is a central (phone app) and a peripheral (some kind of Bluetooth device) and you want to send data back and forth, you don't need to have both central and peripheral roles in the phone app. If you have some special stuff going on, it might be different for you, I don't know. I'm talking about a typical setup.
If you want to send commands to the peripheral, you could write those commands to a characteristic. The peripheral could in turn respond with notifications. This is basically the way I develop a Bluetooth solution, but it can be different depending what you want to achieve.
It takes two devices to communicate with each other.
Device A:
It will be Peripheral device which will be advertising the data. i.e.: Beacons, BLE Hardware
Device B:
It will be Central device which will send request for read,write. i.e.: Mobile
Setup for Device A:
If you don't have Peripheral, there is a way to make your android mobile to act like a Peripheral if your device is supporting that advance feature.
So before beginning, you may simply check that by using following app:
https://play.google.com/store/apps/details?id=com.kyriakosalexandrou.bluetoothsupportcheck
To make your device act like Peripheral, you may install following app which simply simulates the GATT and advertising:
https://play.google.com/store/apps/details?id=com.ble.peripheral.sim
Important: Setup service and characteristics based on your requirements, make sure characteristic is write enabled if you want write data on it.
I am developing an Android app which behaves as Bluetooth peripheral role with a service.
When I start advertising, other Android devices searching for devices offering this service, can see my device (and can pair to it without pin) - ok.
But how to enable PIN pairing?
You can force the device has to be paired, when using specific characteristics by protecting them with PERMISSION_READ_ENCRYPTED_MITM or PERMISSION_WRITE_ENCRYPTED_MITM.
The client/central side can force pairing by calling BluetoothDevice.creteBond().
The pairing method itself is determinated by the bluetooth protocol (see this thread)
You dont actually require pairing to be done to transmit/receive data via ble, take a look into this tutorial
I would like to be able to pre-pair bluetooth devices, to save the step of user confusion when using the app. I have discovered that there is a patent for
System, method and apparatus for pre-pairing bluetooth enabled devices.
I am looking at pairing an array of android devices with an array of embedded devices, so when the android device is set up, I can pre-pair it with the devices it needs to communicate with. I have considered maintaining a list of MAC-addresses that can be downloaded and updated by the app.
Is there a way to pair two devices without having to bring them into contact?
My memory is not exact, it's a while ago I poked around in the Bluetooth stack, however, I don't think this is possible.
Basically there is a white list (text file pretty much) which is kept by the system with devices that may connect to your phone, in order to access that white list outside of the Bluetooth api you need to be platform manufacturer. The Bluetooth Api is strongly guarded (by the specification), if you don't fulfill it you can't say your device supports Bluetooth. Pairing is an important part of the Bluetooth security model, I doubt even an oem would be allowed to do this.
One thing you could look into are Bluetooth low energy devices, those don't require pairing prior to connection (you should be able to connect if you have the MAC address), only Bluetooth classic requires pairing.
More info:
https://developer.android.com/guide/topics/connectivity/bluetooth-le.html
No its not possible unless you make changes to the ROM.
If the use-case supports,you can have ble devices advertising data in a pre-defined format so that the app detect your devices.Once you have recognized your devices,you can internally send a pairing request.
I am developing an application which connects devices over bluetooth and exchanges messages. It works fine for paired devices, but I would also like it to automatically pair devices that are not paired. Like for example it could store and use the same PIN for pairing requests, I just dont know how to manage this request programatically in my applciation, how to automatically set and send the PIN when you get a pairing request and how to initiate such a request with the predefined PIN code.
Any snippets or thoughts would be highly appreciated! :)
EDIT:
I know its risky, I am developing this app for emergency situations only where no other means but bluetooth is available. Also is there maybe a way of premature pairing with devices without even connecting to them? Like lets say there is a list of MAC Addresses of those devices and I can use them to generate a bond with that devices so that they appear paired on my device?
You can't do this. To do what you want to do would create a huge security risk. Think about it, my device just comes anywhere in bluetooth range of yours and now I can send you anything I want without you knowing? You can't really do this and I highly recommend not trying to subvert it.
Reflecting the setPin method allowed me to send the pin automatically to the other device. I had to implement it in a broadcast receiver that is listening for pairing requests. Although I cant get rid of the dialog it just stucks there on the screen and I dont know how to close it (programatically) and continue the bonding procedure since this dialog is called from inside connect() which is a blocking method. I am not giving up on it yet though :)
With Bluetooth version 2.1 and above there is a method of pairing called the 'just works' association model. This is the lowest security method of pairing and has no protection against man-in-the-middle attacks.
However, this will provide a secure, encrypted link without the need to exchange pin numbers or verify device ID.
The API on different platforms may differ but the underlying HCI messages require that you indicate that your device (or one of the devices) has the following IO capabilities:
No Keyboard, No Display.
As you might have guessed, this is a mode for very
simple devices that use Bluetooth, such as a speaker or headphones.
If you can find the API to configure that, then the 'just works' association mode of Secure Simple Pairing will be used for pairing.
The next step is to store the link keys e.g. bonding. Many devices e.g. mobile phones, will still create a dialogue box to the user to ask if they want to 'remember this device', as user authorisation is specified by the BT specifications... but that's another problem.
I am currently working on the creation of an application for mobile devices with Android which should be capable of sending and receiving messages through local means like wifi and bluetooth. After making a research about it I found out that Android doesn't have a native wifi ad hoc functionality and that the only way to achieve that is through rooting your device and patching the wpa_suplicant and some other similiar methods which are not generic for every device.
Synopsis of what I am trying to achieve:
An application for Android that scans for devices nearby and tries to connect to them automatically. If the other device also got this application isntalled then it automatically accepts any connection request it receives and when the connection is established it sends back a message which ensures that it has this app installed so that both can start exchanging messages automatically and the users don't have to allow/deny any of the sending/receiving in real time.
My questions are:
Is there any way of sending messages through wifi between 2 android
devices without the use of internet?
Since Ad Hoc is not supported, is there any alternative?
In case the answer to 2 is no , then is it possible to make one of
the devices to be an access point so the other can connect to it and
vice versa.
As for bluetooth, is it possible to skip or automate the allow/deny
pop up of an incoming connection and the pairing procedure?
I'll be glad if you could give me an answer to those and/or any suggestions.
You'll be able to communicate between two devices over wifi without a router/access point using Wifi Direct (P2P) in Android 4.0.
Otherwise, I don't believe you can achieve this over Wifi (bluetooth would be the next best alternative). Since 2.2 you can set your phone up to be a Wifi Access Point (for tethering your device's network connection), but during this time, the Wifi hardware is unavailable for normal use. If you had 3 devices it could work (1 AP, 2 connecting to it).
Is this for a constant connection, or a one-off small delivery? You could use NFC if you want to transmit a URL for example (Android Beam integrates this type of sharing in Android 4.0, but could implement it in 2.3).