How is bluetooth low energy implemented at a device driver level in linux?
Is there a new bluetooth stack code for every new bluetooth version ?
Bluez is the stack for Linux Bluetooth. New version of Bluetooth have resulted in changes in the code, but it's not a complete rewrite or anything drastic like that. Newer versions of Bluetooth are typically extensions of the existing protocol with the exception of Low Energy. Low Energy is completely supported at the kernel level in Linux, but there aren't a lot of convenience libraries for higher level interaction with LE.
Due to the incompleteness of Bluez with LE I've had to interact with the kernel code directly in order to implement functionality with LE. Also, I had to use older kernels that aren't supported by Bluez 5.x and had to use Bluez 4.x.
Already Tim and jhonnash have provided comprehensive information to your question. However, I would like to add one more information from Android Mobile point of view.
New version of Android uses Bluedroid as Bluetooth stack. This is quite different from Bluez.
Bluez has functionality distributed both in user space and kernel space. All the protocols like RFCOMM, HCI and L2CAP are implemented at kernel level and Profiles are implemented at User space. As Tim mentioned, to support Low energy, Bluez has to provide support at kernel level as well as at user space. This some times get difficult to track and understand. Any new changes may require modification in kernel as well as in user space code.
On the other hand, Bluedroid has some advantage over Bluez. Bluedroid has implemented its complete functionality at user space. Due to which any new functionality only needs to be added at user level code. No dependency on Kernel code.
Also, to answer your question of "Is there a new bluetooth stack code for every new bluetooth version ?" No complete rewrite is required for new version of Bluetooth as Bluetooth new versions are backward compatible, so only those portion of codes are added to the already existing stack which is new.
Regards
As your question is not completly clear that's why I also try to give all the possible protocols available to access bluetooth low enery stack for linux.
In UHID Driver "HoG (HID over GATT/Bluetooth-Low-Energy): GATT is a Bluetooth protocol implemented in user-space. When user-space opens an LE (low-energy) connection to a Bluetooth device, the device can advertise HID capabilities via GATT."
As GATT service is properly defined in this link.
There can be other protocols than GATT to access the Low-energy devices. HID Over GATT implementation is done in this manner.
Related
Initially I built the Zephyr bluetooth application for native linux and run it in conjunction with Bluez on a BLE controller.I understand that in this, Linux OS and Bluez are used along with Zephyr host stack.
Now, I have flashed bluetooth application from Zephyr stack (samples/bluetooth/beacon)to NXP board successfully. Here there is no bluez used.
For this case, I have a few basic understanding questions:
1. Is the OS functionality also embedded in the bin file that is created after application is compiled. I mean I understand bluetooth stack is Zephyr, but which OS is used on board ?
2. Also, is there any functionality similar to hcitool in Bluez in Zephyr bluetooth stack?
3. Is there any functionality like btmon or hcidump?
To answer your questions:-
Zephyr is an OS itself - it is a Real-Time Operating System (RTOS)
that runs on top of many different types of hardware, just like how
Linux is an operating system that runs on top of many different
hardware. Zephyr is mainly written in C and under the hood talks
directly to the specific processor using its registers and the
vendor's stack. You can find a list of all supported boards
here.
Not identical to hcitool, but there is an hci layer example that
allows you to send raw hci commands. You can find more details on
this here and here. At the end of the day, you may not
need to use hci because it is a low layer and you can probably
achieve the same functionality through higher leve API. All Zephyr's
Bluetooth examples can be found here.
Again, nothing like btmon on Linux how you can see the raw HCI
packets for each command, but Zephyr does support different
Bluetooth logging options depending on the hardware used. More
information on this can be found here.
I hope this helps.
As far as I read about the dev boards, every SoC is capable to use Bluetooth.
I didn't tested it yet, but can I use Android Things with a Bluetooth connection? My question is, how can I enable Bluetooth without an input device? If I want to enable Bluetooth on my phone (with code), I had to confirm it, but this can't be possible on Android Things.
Update: Since the release of Android Things developer preview 3, Bluetooth and BLE are now available.
Old Answer
No. You can not use Bluetooth with the current version of AndroidThings (developer preview 1).
It is said in the known issues part of the release notes that Bluetooth is currently disabled (and so is USB).
It is supposed to be included at some point, but at the moment if you try to get a BluetoothAdapter it does return null.
Android Things will use the latest version of Bluetooth called Bluetooth Low Energy and the only similarity between the two is that they have Bluetooth in the name!
Can I use Android Things with a Bluetooth connection?
Yes, well a Bluetooth Low Energy connection
https://www.link-labs.com/bluetooth-vs-bluetooth-low-energy/
In summary, Bluetooth and Bluetooth Low Energy (BLE) are used for very different purposes. Bluetooth can handle a lot of data, but consumes battery life quickly and costs a lot more. BLE is used for applications that do not need to exchange large amounts of data, and can therefore run on battery power for years at a cheaper cost. It all depends on what you’re trying to accomplish.
Everything you need to know about BLE is written here:
https://developer.android.com/guide/topics/connectivity/bluetooth-le.html
how can I enable Bluetooth without an input device?
You do not pair BLE devices like you used to with the older Bluetooth (but you can use Bonding). Check this out:
Android Bluetooth Low Energy Pairing
https://stackoverflow.com/a/20093695/413127
But as stated by #shalafi Android Things doesn't currently support Bluetooth
i am new to Linux and Bluetooth. i know that the standard implementation of the bluetooth protocol stack is bluez. I know that alsa is not supporting bluez anymore and if you want to use audio over bluetooth, you need pulseaudio. so pulseaudio should support HSP/HFP since version 6 and bluez 5.x. Know i was wondering if i can connect a usb-dongle to my hardwareboard (raspberryPi) there is a serial connection to the board. is that right? so the Dongle has the BT-STack and you can use alsa audio over USB like an USB HEadset?
i hope someone can help me.
The answering this vast addressable question is not that easy. I have few hints which will help you to narrow down.
BlueZ is user layer stack to communicate or use the functionality of Linux Kernel Bluetooth subsystem and provides helpers to developers.
USB Dongle itself doesn't have any stack and I don't really understand your question in that sense. To brief, USB Bluetooth Dongle is just the hardware device with Bluetooth functionalities. To make it functional, you need Linux Kernel Bluetooth system support enabled and either you can directly make use of "socket" system calls to pair,connect etc., or use BlueZ to develop applications with API's
BlueZ itself doesn't provide API's for developers, instead it makes use of the DBus to provide methods, properties and signals with vast range functionalities. Check here
If you interested in Audio Playback using Bluetooth, then you should register your media player and audio sink with BlueZ with according media DBus Interfaces.
To add, I am currently developing a framework library to wrap the DBus functionality provided by BlueZ for friendly development of applications. Check this repo and it is currently in initial development phase.
I am going to have a project that can get data from devices that support Health Device Profile(HDP) in Windows.
I find Bluez but it is only available in Linux. Is there any alternative in Windows? Thank You
There are multiple suppliers of Bluetooth stack for desktop Windows. The only one that I know supports HDP directly is Toshiba (though I've no experience with it). So, instead once can add the HDP support outside of the stack software. However, HDP[1] uses the L2CAP protocol which is lower level that RFCOMM protocol that most apps use, and unfortunately Microsoft's Bluetooth stack does not provide a user-level L2CAP API. I started work on a driver to allow user-mode access to the kernel-level API (provided by MSFT in Vista and later) but never finished it. For the other main stacks BlueSoleil doesn't provide a L2CAP API, but Widcomm does.
[1] http://www.alanjmcf.me.uk/comms/bluetooth/Bluetooth%20Profiles%20and%2032feet.NET.html#_Toc266869895
I want to know how to implement bluetooth protocol stack. Any good links or references will be appreciated. How and from where should I start
Thanks.
All the standards and specs are available from www.bluetooth.org. From the Core Specification to all the BlueTooth Profiles currently available. It might only take you a decade or so to assimilate that lot :)
If you want to play with a BlueTooth stack I would recommend a Linux platform with the Bluez stack. Plus you can check out the source for Bluez itself. There is a Bluez API in almost any programming language you could want.
For devices, aside from a PC dongle, or Bluetooth built in to a laptop, most mobile phones support an amazing number of bluetooth profiles, as do other mobile devices.
If you want to build your own thing, there is an Arduino platform with a BlueTooth module from BlueGiga, pretty sure it only does RFCOMM and SPP though.
There are numerous books, from a programmers POV. I chewed through Bluetooth Essentials for Programmers but found it pretty light-weight. Doesn't go much beyond making an RFCOMM link.
Good Luck!