I'm developing an Android app that manages multiple Bluetooth LE devices such as speakers, lighting devices, various sensors.
For user convenience, these devices have to be 'grouped' together and only accessible through a single Bluetooth connection.
Is programming some kind of custom intermediary hardware to serve as an interface required in this case or are there some better solutions?
It is possible to group bluetooth device by the profiles they implement https://en.wikipedia.org/wiki/List_of_Bluetooth_profiles . In Android the profile of a bluetooth device can possibly be determined like in In Android, how to get the profile of a connected bluetooth device?
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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.
I'm exploring a possibility to emulate Bluetooth TV remote control. And I faced a problem that I can't find any information about the type of Bluetooth, which TV manufacturers use in their devices. If they use Bluetooth Classic (BR/EDR), then I have to implement either AVRCP or HID profiles to fulfil TV remote control functionality. If they use Bluetooth LE, then I have to implement HOGP profile. So, could you suggest to me which Bluetooth profile is mostly implemented in modern TVs with Bluetooth support? If someone has experience with a particular TV model, which supports Bluetooth, then I will be also appreciated for any information about Bluetooth, which is installed there.
My question is very basic.I need to know where does all Bluetooth profile such HID, HFP or HSP loaded in Bluetooth stack? Is it in Host layer or in Bluetooth Hardware Chipset such as USB dongle/module or in both Host and Chipset Side?
According to my understanding, we can implement Bluetooth profiles on Host side using packages like BlueZ but at same time Bluetooth chipset which is connected to Host should need some sort of firmware and logic(like CSVD, A-law ) inside its chipset.
A quote found in BlueZ Android package doc: "Wideband Speech support in HFP it is required that BT chip assumes mSBC codec". This means Host layer can implement that Profile only if BT chipset provides the low-level support like mSBC.
My Answer is like this: " We can build any Bluetooth Profile say 'X' on Host layer if BT chipset is equipped with underlining Low-level firmware which support the Profile 'X'".Please agree or disagree with my understanding.
PFA diagram of my understanding
Position of profile and its low-level firmware
I need to select a USB Bluetooth dongle compatible to Raspberry Pi and customize the HID and HFP using BlueZ.
Advance Thanks to all Bright minds!
There are multiple ways how Bluetooth functionality is implemented in a system based on how much is implemented in the controller and host.
Everything in the controller - App, Upper stack, may or may not HCI(lower and upper stacks communicate through HCI commands and events), Lower stack. Example: Most of Bluetooth Mouse, Keyboard etc, where a single controller is responsible for everything (Bluetooth, RTOS/scheduler, Controlling LED's in the device, etc)
App in Host and lower and upper part of stack in controller. May or may not implement HCI in controller.
Example: Where we use a dedicated Bluetooth chip and integrate it with the Device. Here device will transmit application data to the Dedicated Bluetooth chip. All the Bluetooth protocol related things will be done from BT controller/chip. If you are using an HC-05 module with Arduino module, Arduino will transfer the serial data to the HC-05 module.
App and upper stack in host and lower stack in the controller. Bluez, Bluedroid and all other stacks in Operating systems are of this type. This will communicate with the controller with HCI commands and events.
Example: Mobile phones, Computers, TV with Bluetooth etc (Devices having a powerful Application processor)
So lets assume you are asking about the 3rd type. In this case your assumption is correct. Here all profiles are implemented in the host only. But protocols/codec needed to support them will be implemented in the controller(either firmware or hardware block). For example GAP(For BR-EDR) is implemented in the host but encryption and decryption algorithms are implemented in the controller as Firmware or hardware blocks. For A2DP profiles audio codec/decoders will be implemented in the controller. BT chip then transfers this audio data to host with I2S or other protocols. For BLE Security manager profile, encryption/decryption algorithm is implemented in the host itself, But whitelist, auto connection etc, will be implemented in the controller.
My Answer is like this: " We can build any Bluetooth Profile say 'X' on Host layer if BT chipset is equipped with underlining Low-level firmware which supports the Profile 'X'".Please agree or disagree with my understanding.
For BlueZ use case this is correct. You need to use the controller with the required hardware capabilities(Firmware + hardware resources).
For the scenarios 1 and 2 the profiles and supporting protocols will be implemented in the controller.
I have to test Ble devices with an App on iOS and Android, the scenario is having multiple device sending signals and it is difficult to figure out which device is connecting to what phone.
Is there a better way to test and what are some of best tools for checking the status of ble devices like signal strength and other characteristics.
I've been using LightBlue Explorer to poke at BLE devices to see characteristics and values. It can also emulate devices once it's seen a real one.
I ultimately ended up writing my own Device Simulator on iOS. This lets me generate a controlled BLE service/characteristic, with full control of the device name, advertised broadcast name, and characteristic values.
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.