When connection to a custom BLE device from an app (android and ios) I have two options
a) first pair the device on the phone (like a headset or other devices) and then use it from the app to read and write data
b) without pairing on the phone, go inside the app, search for a device with a specific name or address, and just connect to it and read and write data.
when is one preferred over the other one ?
Its just when it needs to interact in the background or am I missing something?
The devices you see in your phones Bluetooth settings are Bluetooth Classic devices. There are some devices using both BLE and Bluetooth Classic which show up in the settings too, but the settings page is only for the Bluetooth Classic part of the device. Headphones for example are streaming music trough the Bluetooth Classic profile A2DP but might offer BLE services for additional features.
You always have to use a special app to communicate with the BLE part of a device. This could be an app provided by a manufacturer or a generic BLE scanner app such as nRF Connect.
As alexander.cpp already told you in his answer pairing (the exchange of keys) and bonding (saving of said keys) is not required for the communication with BLE devices and only needed if the device requires a secured connection.
Bonding (technically correct term for BLE, often called Pairing in non-technical speech) is mostly for security, we can send sensitive information because the receiver is verified and data is transferred in encrypted form.
Prefer to use bonding if the data is sensitive (means users feel uncomfortable if somebody they don't know receive their data). For example, I consider "current temperature = 25" as NOT sensitive. For detailed explanation, find "Bonding with a BLE device" in BLE guide by PunchThrough.
Also this is a good answer to a similar question: https://stackoverflow.com/a/42916081/10380092.
Your second question about background - no, bonding is not related to interaction in background.
Related
I am looking for a way to scan a device I own and discover "what it can do".
In other words, I'd like to know if a device is able to describe the way you have to communicate with it in order to build some application around it.
In my case it is a simple Christmas light that I'd like to play with but this could be used in different situations.
For classic bluetooth (BR/EDR):
When scanning for bluetooth devices (Inquiry), the bluetooth device will send an inquiry response (if it wants to be discovered) and maybe also an extended inquiry response (EIR). This EIR may already contain a list of services, the devices supports. This is a very fast way to get a picture of a remote device.
Moreover, the service discovery protocol (SDP) gives more information on a device. This takes some more steps. In SDP two devices can exchange their capabilites in kind of ping pong process.
For BLE:
After connecting a BLE device usually a service discovery takes place. The BLE peripheral (e.g. headset or a light) reports its capabilities to the central (e.g. smart phone). Some of these services have predefines functionalities. Additionally, it is free to the manufacturer to add custom services.
I am developing an app that controls a product's operation. The communication is via BLE. My configuration is
App - Peripheral (iOS, Android)
Product - Central (uses Laird BT900 module)
iOS as a peripheral works fine (pairing and bonding) ; Android PIN pairing works fine, but subsequent bonding (or reconnect when in range) there are a lot of issues and termination of connection. I am using the supported list of devices for Android BLE and I also understand that there are many known issues that come with different manufacturers/chipset vendors
The issue I am getting is, as seen by nrfConnect, is with descriptors. Android app doesnt show descriptors when seen in nrfConnect whereas iOS shows. I do not know what is the difference
Is it a common practice to use a phone as a peripheral ? Or is it a risk - because this is a medical device.
Are there any best practices for Android as a peripheral ?
I have following back up plans in case Android issue is not resolved. I think following would work on any BLE supported phones without having any issues with the variability.
Plan A : PIN pairing on every connection with the product. This is the most secure and most annoying
Plan B : Implement just works pairing with a app layer password before taking control of the product.
Question : Is just works safe and encrypted ? Is it snoop-safe or MITM-safe ?
Thanks in advance!
A few thoughts from your questions:
1a. (From my Android experience) I think its uncommon to have the phone be the peripheral. To my knowledge all iOS devices support peripheral mode but only a very small subset of Android devices are able to support it. I say this because I've been experimenting with BTLE beacons using the AltBeacon library. From this work I have discovered that only certain Android phones can broadcast BTLE advertise packets. Given that BTLE advertising is the first step in initiating a BTLE session I imagine that this prevents many Android phones from being compatible with peripheral mode.
If all of your users can use an iOS device, then you're set, otherwise this may be a problem.
1b) I can't speak to the specific risk of using a mobile device with your medical device, that depends on what the medical device is doing and how you're using the mobile app.
2) See 1a
3) The specific encryption scheme you used is also based on your product's risk profile. I would say that Just Works is not an ideal solution. The just works pairing process is not snoop-safe and can be re-initiated via a MITM. Other than that I can't speak to the strength of BTLE encryption.
I'm not a ble guru, I worked on some modules to expose some simple service with pairing and bla bla :9
One of our customer ask me if it possible to control mcu gpio, with a beacon service running. For what I know beacon standard is only a lighthouse to check the proximity (streaming simple packet uuid, signal strength etc etc), and the only way to do something like this is to expose a new service running concurrently with beacon ( in practice send multi type of packets). I don't want pairing (beacon<->device app) and don't worry about race condition, if multi devices set/reset a gpio, it's not my business.
I found something similar https://community.estimote.com/hc/en-us/articles/217429867-What-is-GPIO-How-to-set-it-up-, what you think about?
There are libraries or eddystone's extensions to do that? Some project on github?
We prefer to work with Nordic ble module, but if you know solution based on other mcu, you are welcome.
Thanks for your help
Standard beacons (iBeacon, Eddystone, AltBeacon) are transmit only devices. They simply send out advertisements at a fixed rate with a unique identifier. Some manufacturers expose proprietary configuration interfaces as read-write Bluetooth LE GATT Services. But there is no standard GATT Service that does this, and the manufacturer-specific schemes are designed specifically to set beacon identifiers and other operating parameters.
I don't think there are beacon-specific libraries or extensions that will help with this, beyond standard Bluetooth LE SDKs for iOS and Android. In order to accomplish this goal with a Nordic BLE module you would need to build your own custom system:
Write custom Nordic firmware (that sits alongside beacon transmission firmware) that exposes a new Bluetooth LE GATT Service. The service would expose a writable GATT Attribute that would control the GPIO pin.
Write custom mobile app code that connects to this GATT Service (CoreBluetooth on iOS and android.bluetooth on Android), and writes to the GATT attribute to control the pin.
One thing you must be careful of is that connecting to to a GATT Service will typically stop a Bluetooth Peripheral from advertising (meaning it won't transmit as a beacon). So you may wish to drop the connection quickly to prevent mobile devices or other Bluetooth Centrals from stoping the beacon transmissions.
I was wondering if there's any way that I can control BLE device pairing specific to my app running on mobile device?
I do not want to write my own bluetooth profile so that only my app can talk to the BLE device instead i want to standard profiles available in BLE device but when it's paired to my phone, only my app should be able to communicate to it and none of the other apps should be able to communicate.
No don't do that.
If you MUST then you should encrypt your data with a key only your app knows.
Bluetooth Low Energy is supposed to be open and free for all.
What is the purpose for you to block others? Preventing them to block your service?
Then use some pre-shared key to verify that it's your app in both sides and close the connection if it's not.
Can a WindowsCE device connect so more than one BlueTooth device? The device needs to both serve as a BlueTooth hands-free speaker for a phone and connect to a third device via a serial BlueTooth connection.
Can an application do this without the need of a speciel driver?
You must understand that Windows CE is a modular OS and any specific platform capabilities are implemented by an OEM. An OEM can create a Windows CE device with absolutely no Bluetooth support or they might choose to implement just a Bluetooth client profile (say as a bluetooth audio device) or they may choose to implement a Bluetooth server so they can consume a Bluetooth serial device. They may also choose to implement both. Beyond what the OEM does in software, the hardware itself might allow only one or the other (or both or neither for that matter).
The short of this is that we can't actually answer your question becasue there is no generic answer that fits all devices. You have to ask the Device OEM what they support and if they can extend that support if they don't support what you need.