With the last release of BlueZ (5.30) the highlight was the completion of the GATT D-Bus apis. My goal is to programmatically (in C), as a BLE client:
scan for ble devices (which I can do with the hci layer)
Connect to an advertising BLE device
Get the UUIDs
Execute Read and Write to handles
The BlueZ community is strongly suggesting to use the GATT-Dbus api to accomplish this. After multiple searches and head scratching I was not successful to find a proper way or example that would perform this through GATT-DBUs api. It seems more complicate than just use directly the GATT layer. Unfortunately BlueZ removed direct access to make calls to gatt.
I'm very close to just pull the GATT source files out from Bluez, compile it as it's own independent library and directly use the GATT layer and calls to connect and execute reads/writes to ble device server. I know it is not the suggested way compared to the DBUS-GATT api but I'm out of options.
If anybody has any input on this or suggestion (with some sample code) please advise.
thank you in advance!
The best way to start with DBUS GATT API is to hace a look at the source code here: http://git.kernel.org/cgit/bluetooth/bluez.git/tree/
Under client folder you can find a full sample of how to use the DBUS GATT API. Actually that is the source of bluetoothctl tool.
Note that DBUS GATT API is still experimental but you can enable it running bluetoothd service with -E flag.
I had a similar issue which is to interact with a BLE device with a GATT C/C++ API.
In my case I had to use Bluez v4.101 - the latest Bluez version available in Ubuntu 14.04 LTS (read my story). In Bluez v4.x, there is no DBus API.
And actually, I have recently worked with Bluez v5 DBus API and I discovered if you do not use at least Bluez v5.39 (from April 2016) it is likely you will have issue with the DBus API. And as said before the DBus API is still experimental.
So to solve my Bluez v4.x dependency I had to pull the GATT source files out from Bluez and create my own library 'gattlib'. The project is Open-Source to encourage feedback and contribution.
I am using this library in my own GATT client project.
I wrote few examples to help people to start using it see the folder /examples of the project.
EDIT March 2017: I have just added DBus support to gattlib (https://github.com/labapart/gattlib/). From Bluez v5.42, gattlib automatically uses DBus API (DBus gattlib backend can also be forced when building the library to use it before v5.42).
Related
I have been looking around for a simple Bluetooth LE library in C that allows me to scan for BLE devices, connect and receive periodic notifications from a given service UUID from the BLE device. Something that directly works with Bluetooth sockets and libbluetooth(created from BlueZ) and not using DBUS. Pairing and security functionality are not required.
Came across https://github.com/labapart/gattlib. Appears to be good but uses dbus API and has dependency on libdbus, glib, so on. To use this library, there is an additional 5MB of libraries required, hence decided to go without dbus. We do not have space on our device to support 5MB of bluetooth stack on compressed rootfs image. The total size of our rootfs image is 9 MB. The bluetooth stack with dbus itself appears to be more than 50% of our rootfs size.
There is also - https://github.com/edrosten/libblepp which is in c++ and doesn't use dbus. This would require to write a C wrapper to be used in C programs and also overhead of C++ constructs such as compiler generated copy constructors, assignment operators and so on. Also issues in cross-compiling.
Target board is Xilinx Zynq running Linux and the build system is buildroot.
Please suggest.
Thanks
Found a solution, it may be of help for someone...
After searching and going through Linux Conference and IOT conference videos on youtube, figured that Bluez has light weight executables and the code is present in src/shared folder of Bluez. For btgattclient.c produces "gatt-client" executable when compiled which does the same functionality as "gatttool" and is not dependant on bluetoothd or dbus. The only dependency it has is on glib-2.0.
This is helpful if we need lightweight tools when the OS has no bluetoothd running or has no dbus library installed.
Thanks
If you want to use BlueZ for BLE communication, the only supported API is the D-Bus API. Everything else is either discouraged or deprecated.
If you want something more minimal and/or not use BlueZ at all, you can use the HCI_CHANNEL_USER feature in Linux to get raw access to the HCI connection in the kernel. With this you can use any Bluetooth Host stack software or write your own minimal if you only require an extremely small subset.
Questions asking for software library recommendations are not allowed on Stack Overflow due to the possibility for opinion-based results though.
I will be asking a very subjective question, but it is important as I am looking to recover from failure to effectively use BlueZ programatically.
Basically I envision an IoT edge device that runs on a miniature computer (Ex: Raspberry pi or Intel Compute Stick). The device would then run AlpineLinux OS and interact with Cloud.
Since it is IoT environment, it is needless to mention the importance of Bluetooth BLE over ISM band. Hence the central importance of being able to customize and work with BlueZ.
I am looking to do several things with BlueZ BLE including but not limited to
Advertising
Pairing
Characteristic
Broadcast
Secure transport of data etc...
Since I will be needing full control over data, for data-processing and interacting with cloud (Edge AI or Data-science on Cloud) I am looking at three ways of using BlueZ:
Make DBus API calls to BlueZ Methods.
Modify BlueZ codebase and make install a custom bin.
(So that callback handlers can be registered and wealth of other bluez
methods can be invoked)
Invoke BlueZ using command line utils like hcitool/bluetoothctl inside a program using system() calls.
No 1 is where I have failed. It is exorbitant amount of effort to construct and export DBus objects and then to invoke BlueZ methods. Plus there is no guarantee that you will be able to take care of all BLE issues.
No 2 looks very promising and I want to fully explore how feasible it is to modify the BlueZ code to my needs.
No 3 is the least desirable option, but I want to have it as a fallback option nevertheless.
Given my problem statement, what is the most viable strategy forward? I am asking this aloud so that I do not make more missteps and cost myself time and efforts.
Your best strategy is to start with the second way (which you already found promising) as this is a viable solution and many developers go about this method in order to create their BlueZ programs. Here is what I would do:-
Write all the functionality of the system in some sort of flowchart or state machine. This helps you visualise your whole system and what needs to be done to reach your end goal.
Try to perform all the above functionality manually using bluetoothctl and btmgmt. This includes advertising, pairing, etc. I recommend steering away from legacy commands such as hcitool and hciconfig as these have been deprecated and have a very different code structure.
When stumbling upon something that is not the default in bluetoothctl/btmgmt or you want to tweak the functionality, update the source to do so.
Finally, once you manually get the system to perform the functionality that you need (it doesn't have to be all, it can just be a subset of the functions), you can move to automating the whole process. This involves modifying the source for bluetoothctl/btmgmt commands so that instead of manual intervention, everything would be event-driven.
This is a bonus, but if you can create automated tests using python or some other scripting language, then this would ensure that your system is robust and that previous functionality doesn't break when adding new ones.
By the end of this process, you'll have a much better understanding of the internals of bluetoothctl/btmgmt and D-BUS APIs that you might be able to completely detach your code from the original bluetoothctl/btmgmt or create the program from scratch.
You probably already know this, but when modifying the tools, this is the starting point for the source code:-
bluetoothctl - client/main.c
btmgmt - tools/btmgmt.c
For more references on using bluetoothctl commands and btmgmt, please see the links below:-
BlueZ D-Bus C or C++ Sample
Bluetoothctl set passkey
https://stackoverflow.com/a/51876272/2215147
Bluez Programming
Linux command line howto accept pairing for bluetooth device without pin
https://stackoverflow.com/a/52982329/2215147
Bluetooth Low Energy in C - using Bluez to create a GATT server
I hope this helps.
I am currently evaluating IoT platforms which can connect to devices and controllers, then collect data and do some analytics
To start with I have this device "JACE 8000" which runs on Niagara platform, which has communication protocols like obix, mqtt etc
I would like to know if Kaa already has any existing module or plugin for this?
If not how to build a new one? and how easy is it to develop a new plugin
It appears that Kaa's preferred choice of protocol is MQTT. Niagara N4 happens to provide an abstract implementation of an MQTT driver, so I'm confident that would probably be your best route for development if you wanted a JACE to communicate with a Kaa network.
To go into any more depth is difficult here because you really need to be either a certified Niagara engineer or developer and have access to a workbench, documentation, and so on. The Niagara framework is a big beast!
I am very new to Bluez and I want to create some custom profile (GATT server) with one service and 2 Characteristics by using Bluez5.49 version.
I don't know how to start. I want to write this as a C application via Dbus. I don't want to use any command line operation for advertise.
I have doubt like if I advertise my device by using Dbus how I know whether I got scan request from Master (Central device). Which Dbus method is used to read the event of the BLE? How to proceed further?
Is there any option in Kaa when device contacted the Kaa platform with some data, Is it able to send the same information to our external systems through message broker? For example when a temperature sensor updated the current temperature value to the Kaa, Is kaa able to send the same information to the Messaging brokers like ActiveMQ.
Maybe you can try the Kafka or Flume appender of Kaa.
I try to use the Kafka appender to send the data from some sensor to storm server like below reference and it works fine.
https://www.kaaproject.org/iot-real-time-data-processing-in-storm-using-kaa/
And you also can custom your appender by following below url:
https://kaaproject.github.io/kaa/docs/v0.10.0/Customization-guide/Log-appenders/
There are many possibilities to do that which are better or not depending on your particular use case.
But, usually the most efficient way would be to use one of the existing Log Appenders that are running on the Kaa server side and were specifically created for such messaging.