I'm trying to implement a Bluetooth (BLE) gateway into a project to transfer data between hardware and a mobile device with an application. The hardware is not unique, it could be mass produced with the controller having the same program flashed into it.
If 100 of the hardware product is made, powered up sitting side by side, what is the best way to set up the information that the BLE broadcasts to advertise so that it can be received by a mobile device, and only 1 hardware and mobile device can be connected at any time.
For example, if you have 3 of the same fitness tracking watches side by side, and you only want to connect to 1 of them, how do you distinguish which is which on say the phones bluetooth pairing menu.
Does each of the manufactured hardware need to have a unique ID that shows on the mobile device (eg ABC11, ABC112, ABC113 etc), and how do you program 100 unique programs into the hardware quickly.
On the other hand, should each of the hardware have the same ID broadcast, and then the user just hopes for the best if the correct hardware is paired.
(BTW, the hardware is an arduino based microcontroller using a BM70 BLE module. neither of which are intended to be modified by the user)
Assistance appreciated.
Thanks. Nunya
You do not have to manually program a different MAC addresses for each device, the BM70 module is the one that provides the BLE MAC address and they are supposed to have unique ones. Sometimes manufacturer recycle (reuse) the addresses, but I think the chance to hit a MAC twice with 100 devies is pretty low.
If your devices are all the same and use the same program they all offer and advertise the same BLE service. The service and containing characteristics are the feature that distinguishes your devices from other BLE devices. A true BLE device that does not also use Bluetooth Classic will not show up in your phones bluetooth settings or pairing menu. BLE requires a dedicated app where you scan for BLE devices and idealy filter for the special service you are using to only find your own devices.
To distinguish between 100 devices placed next to each other (if this even matters since they are all the same) you need to either read the MAC address and prit it on a label for each device or use some status LEDs to show the connection status on your arduino. If you connect to one device the LEDs could start blinking to show which device you are connected to.
Related
I've built a dual mode Bluetooth device using the BT 121 from Silicon Labs. The device implements SPP over the classic connection. The device name of the classic node is "XYZ Classic". It also implements a custom service (128-bit UUID) in BLE. The device name of the BLE node is "XYZ_BLE". Both nodes have the same MAC address.
When pairing under 'Bluetooth' settings, sometimes I will see 'XYZ Classic' and sometimes I will see 'XYZ_BLE'. It seems random which one it will pair to but many Android devices I've tested have a tendency to want to pair to the classic node. After pairing, a connection over classic/SPP ALWAYS works. However, I can only connect to the custom service if paired to the BLE node. If paired to classic I can see non-custom BLE services but not my custom service. To summarize:
Function Classic Pairing BLE Pairing
Spp Works Works
Cust BLE Doesn't Work Works
When I pair in code (Android) the problem also happens despite the fact that I search for the devices named 'XYZ_BLE' and then pair to the device returned. I've looked but I can't see a way to force Android to pair to the BLE node.
My only workaround thus far has been to modify my BT 121 firmware to not allow bonding in classic mode. This is not an ideal solution has any Bluetooth Classic only devices will not be able to bond with my device (In reality this might not be too big of a problem but I have one tablet in my possession that only has Bluetooth Classic).
It should be noted that I've used 'BLE Scanner' from the play store to verify that my custom service works/doesn't work depending on the pairing mode. In other words, it's not just my code. :)
So, does anybody have any ideas on how to force Android to pair to the BLE node?
I see similar issues. Some hints:
Android behaviour differs dependent on the bit flags you set in the BLE advertising. There is for example a bit called "no br/edr support" or so. There are also bits telling explicitly that br/edr dual role is supported.
Also ble pairing may be enforced if you access a characteristic which returns a "not authenticated error" from a ble app. At least on iohone, the os will initiate the ble pairing automatically.
I have been doing a ton of research on this project I want to do, probably read every SO post (bluejacking, RFCOMM, beacons, etc...) and my head is spinning.
I want to create a system at home, using Arduino (with bluetooth le) that will scan bluetooth and detect when my phone or any of my family members phones are in proximity. Whether this is a MAC scanner or simply getting the friendly name. I would also like to get the RSSI. I dont need to do accurate distance measurement but I would like to know approximately how close they are. Does anybody have any suggestions for this approach? I know I can create an app on the phone and have it become a beacon and this may be an option but I am concerned with Android, it would have to be Marshmallow 5.0 at a minimum. I would like support to be a little lower than that, like JB or KK. So, it seems like there should be a simple scan, just looking for the MAC or name. That is all I really need.
That said, the main question I have is, can you scan for and see bluetooth devices in range if they are already paired to something? Like a Bluetooth headset? I understand bluetooth is point to point but does it allow multiple connections or at least broadcast the mac or name when paired?
This question, along with any general suggestions will help me out tremendously!
Thanks!
Bluetooth Discovery from the Listener involves Listening for Bluetooth Inquiry packets(RX) and inquiry response (TX).if done continuously this will deplete the battery. Hence most devices (including Mobile Phones and Headsets) has a policy of when to be discover-able and connectable. Headsets in particular are discoverable only when they are instructed and connectable until one device is connected to it ( There are probably exceptions where the headset has the capability to be connected to multiple phones at the same time). Most Mobile Phones are discoverable only when they are in settings screen ( Android,IOS and Windows Phones), but unlike the headset case they are connectable.
so one option with the MobilePhone is to see if it is possible to connect to them after pairing once ( for example by trying a service search on the remote device and see if it returns the service attributes, this internally makes a connection and indirectly ensures the presence of the device).
if you are specific about a mobile phone which is already paired then you might need to establish a higherlayer connection ( such as SPP) with Authentication and encryption. This would force a two way check between devices to see whether they are already paired. other less secure option is to rely on the Phone (Android and IOS phones doesn't generally Allow a higher layer connection without encryption/pairing) and try to establish an SPP connection to the phone.
Another option is to use Bluetooth-LowEnergy. But Note that security in BT was superior to BLE till BTv4.1 and same on BTv4.2.
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'm not a developer but I'm curious about the connectivity options between smartphones.
Looks like BLE is the only technology that is available on both Android and ios that could make an connection possible in the foreground, but is able to scan in the background?
If I walked around with my phone in the pocket, could it scan in intervalls for other devices`UUIDs/mac addresses and save the data realibly without the process being shut down after a while?
the app would have to work between Android phones, ios Devices,
and Android phones-ios Devices.
I dont want a stable connection. I'm only speaking about gathering UUIDs and mac adresses in the background. whichever is more suitable to uniquely identify a device.
Thanks in advance.
iOS devices with BLE support can act as the peripheral and/or the central role. The peripheral advertises its services, and the central discovers them (via scanning). You need Android 5.0+ to support peripheral mode.
Once a central discovers a peripheral, the central can obtain advertisement details from it, including a unique peripheral ID. This is similar to a MAC address, though some peripherals randomly generate these IDs.
In general, an iOS or Android device acts in the central role and it doesn't advertise anything. There is nothing to discover. However, you could write an app that acts as both a peripheral and a central.
On iOS, your app can perform both BLE roles in the background (your app doesn't need to be in the foreground).
You would want to do background tasks responsibly as both advertising and scanning require the radio, which uses a significant amount of power (drains the battery).
There are many issues with the current BLE stack on Android (e.g. using WIFI and BLE at the same time because they share the radio). The BLE API first became available for Android with 4.2.
The iPhone 4s and later has BLE with the API first available in iOS 6.
I have the bluetooth mac-id of the target device. The bluetooth however is in hidden/not visible mode.
Both phones are android. (Non-root).
I did my research and I * know * that I can CONNECT to a device (in most cases) if I know the mac-id, however I want to just scan for proximity and NOT connect i.e. if the target device is in bluetooth range and I know its mac-id, can I * just * know if its in proximity (or in loose terms, scan for it?)
The short answer is no, you cannot discover undiscoverable Bluetooth devices.
Having a device in undiscoverable mode is a security measure implemented by manufacturers to prevent abuses such as device tracking. This make a standard bluetooth adapter (such as yours) completely unable to state whether an invisible/undiscoverable device is close or not.
However, it turns out this kind of security is not optimum and has been broken recently. You can find here Michael Ossmann's work on Ubertooth, a small Bluetooth adapter able to detect undiscoverable devices. You can find here a great presentation of what this is, build this dongle using open source plans and even buy his dongle.
EDIT :
It is possible to know whether a bluetooth device is around, even if he is in an undiscoverable mode, by knowing his full MAC address in the first place.
The technique is to try a PAGE request, sending all the 6 bytes that are composing the seeked Bluetooth host MAC identifier. A PAGE request allows one to connect with a Bluetooth slave when knowing his BT ADDR. Devices that are in undiscoverable mode does not respond to inquiry scan (device discovery intent), but they do respond to page scan which is used by a device wanting to connect to an another previously known device.
You might be able to do what you intend by using Bluesniff, a security proof of concept allowing you to discover hidden devices. It might support page scanning.
Note that this is to be taken as an educational resource, and I do not encourage this kind of practice in a commercial application.