Comment 0. This article is taking things a step further and uses a Python script on Linux to access the sensor data on the BLE device:.Laptop and multiple SBricks - no problem with gatttool
Accessing Hexiwear sensor data with Python. Python is a powerful scripting language and can be used for all kind of automation. First, make sure that latest packages are used:. Install the pexpecta package to control other applications from Python:. With ' pexpect ', I can spawn a process from Python and then control it like I would type in the commands manually. I send the string to the gatttool spawned process. I have specified that it should timeout after 5 seconds. The handle 0x30 is for reading the accelerometer values.
The gatttool would print something like this:. With child. For example That way, I get substrings of x, y and z accelerometer values. To transform the hex string in little endian into a signed bit number, I use the following Python sub-function:. For example, the numerical value would be 1. With this, I can print the x, y, and z values:. Instead of printing the values, I can store them to a file or whatever I would like to do.
Below is a Python script similar to the one above, which sets the Hexiwear's current date and time using the Unix time seconds after from the Raspberry Pi:.
Python is great for scripting things. With the pexpect Python class, I can spawn a process and then send and receive strings. See the original article here. Over a million developers have joined DZone. Let's be friends:.
DZone 's Guide to. The combination of Python scripts, gatttool, BLE, and Hexiwear lets you send and access data over your devices with a few handy scripts. Free Resource. Like 3. Join the DZone community and get the full member experience. Join For Free. This article is taking things a step further and uses a Python script on Linux to access the sensor data on the BLE device: Accessing Hexiwear sensor data with Python.
Writing Unix time to Hexiwear. Like This Article? DZone Article. Free DZone Refcard.First up, we need to check our bluetooth connections, which work a bit like our network connections, but instead of ifconfig we use:. There is a hcitools which allows scanning of bluetooth low energy devices. This scans through and picks up any bluetooth devices around. So we know the MAC address and can use this to connect to the device and try and interact with it.
We need to connect to the device, we can use the MAC address to do this. To dump all the data in a readable format, a tool called bleah is needed or bettercap also does it, if you can get it working!
As bleah has been deprecated I had to download it from a previous commit and download the zip, rather than doing a simple git clone. In addition to this output, the device now has a blue light to indicate that something is connected to it.
So this is great, we now know all the challenges! I guess now is just a case of working through them! Tweaking the request we get:. I think this is flag 1 done, so we can read the score to see what we have.
Now as bleah has to connect and disconnect each time. It might be better to move back over to gatttools in interactive mode. We got data back, it looks like hex. Looking at the github page, this is the case, coupled with the MD5 hash is always only 20 characters long, so from the github page, the submit command is:.
This should be straight forward! The only way I know to fix that, is to exit the window, which in our case means coming off the ssh session and closing that tmux screen!
I was meant to write and read from not ! This seemed to work, however the score was still 2! As the values that we input get converted to hex, we can skip that part and just put in the hex value directly.
Writing the hex 0xC9 to handle 58 is this challenge. Again we should be able to do the same as above, just changing the handle value. We are always providing the hex values for the handles, maybe the actual handle is the plain number.
So if we can write a script to increment the number, convert it to hex within that range it should work. We need a simple for incrementing loop which is converted into hex each time. This seems to work! This takes that converted value and adds it into the end of the command.GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together.
If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. Despite the popularity of BLE, we have yet to find a good programming interface for it on desktop computers.
Since most peripherals are designed to work with smartphones, this space is neglected. One interactive interface, BlueZ's gatttoolis functional but difficult to use programmatically. BlueZ itself obviously works, but the interface leaves something to be desired and only works in Linux. The BlueZ backend is not supported by default as it requires pexpectwhich can only be installed in a UNIX-based environment.
If you wish to use that backend, install the optional dependencies with:. The primary API for users of this library is provided by pygatt. BLEBackend and pygatt. After initializing an instance of the preferred backend available implementations are found in pygatt.
Note that not all backends support connecting to more than 1 device at at time, so calling BLEBackend. It's identical except for the initialization of the backend:. This example uses the gatttool backend to connect to a device with a specific MAC address, subscribes for notifications on a characteristic, and prints the data returned in each notification.
While debugging software using pygatt, it is often useful to see what's happening inside the library. You can enable debugging logging and have it printed to your terminal with this code:. If you provide the COM port name, but still get an error such as WindowsError 2, 'The system cannot find the file specified.
Skip to content. Dismiss Join GitHub today GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together. Sign up. Branch: master.With the rapid growth of IoT accelerating development in Bluetooth technology, constant efforts are being taken by the Bluetooth Special Interest Group SIG to increase the transfer speed with a maximum focus on beacons, healthcare entertainment, and fitness.
Compared to classic Bluetooth, BLE is intended to use lesser power while maintaining similar communication range. BLE is an "always off" technology and only transmits short amounts of data when required. This significantly reduces power consumption making it ideal to use in cases where a persistent long term connection is required with a low data rate. BLE is perfect for a TV remote but not for a wireless media streaming device which needs a large amount of data to transmit.
Bluetooth Low Energy is built into many of the gadgets that we use today. From smartphones, smart televisions, advanced technologies such as medical equipment to a basic devices such as our coffee machines, all use BLE.
BLE was conceived with an emphasis on better pairing speed and energy efficiency. The fact is - BLE is just a protocol. Even the strongest cryptographic protocol has been known to fail due to the random number generator not being "random enough.
Thus, it can be said that the security of BLE lies in the hands if its implementers. While all Bluetooth Low Energy devices were developed with the principal motive of enhancing user experience, did security take a backseat during the process?
This is responsible for the connections and advertising in BLE. GAP is responsible for the visibility of a device to the external world and also plays a major role in determining how the device interacts with other devices.
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The following two concepts are integral to GAP:. Peripheral devices : These are small and low energy devices that can connect with complex, more powerful central devices. Heart rate monitor is an example of a peripheral device. Central devices : These devices are mostly cell phones or gadgets that have an increased memory and processing power.
The peripheral device will send an advertising data once every 2 seconds. If the central device is ready to listen to the advertisement packets, it will respond with a scan response request. In response to this request, the peripheral device will send a scan response data. Thus, the central and peripheral device gets advertised and connected with each other.
Making use of a generic data protocol known as Attribute Protocol, GATT determines how two BLE devices exchange data with each other using concepts - service and characteristic. This protocol stores all the service and characteristic in a lookup table using a 16 bit IDs as specified by the Bluetooth SIG.
Services Services are simply defined as a cabinet which can hold many drawers in it, which in turn are called as characteristics.
A service can have many characteristics. Each service is unique in itself with a universally unique identifier UUID that could either be 16 bit in size for official adapted services or bit for custom services. Characteristics contain a single data point and akin to services, each characteristic has a unique ID or UUID that distinguishes itself from the other characteristic. For example HRM sensor data from health bands etc. Linux offers the best support for BLE.
The --characteristics says Characteristics Discovery and the --char-desc says Characteristics Descriptor now what is the difference?
Using Python, Gatttool, and BLE With Hexiwear
If i run them both against the same BLE device i get diffrent handles for the same uuid? Think of descriptors as metadata about the characteristic, or "defined attributes that describe a characteristic value". For instance you may have a characteristic which holds some measured value, which then also has a descriptor that states the acceptable range for the value. If you read the characteristic, you are going to get the value itself; read the range descriptor then you are going to get the valid range.
Some descriptors have been adopted into the Bluetooth specification and have assigned numbers and some may be custom without general documentation. Learn more. Asked 3 years, 3 months ago. Active 3 years, 3 months ago. Viewed 4k times. Default: low -I, --interactive Use interactive mode The --characteristics says Characteristics Discovery and the --char-desc says Characteristics Descriptor now what is the difference?
Peter Peter The wording is unnecessarily confusing. Active Oldest Votes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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In order to use Bluez, I needed to install Linux on a virtual machine. If you need a helping hand installing Debian may I suggest this step-by-step guide? Note: make sure you uninstall Bluez if it is already installed. Note: —enable-library will enable use of the library so you can create your own applications utilizing the Bluez stack. You must do it manually:. Note: if you get a Failed to attach USB device error, you may need to create a device filter that will autoconnect.
More information on creating a device filter here. Note: if nothing shows up you may have to reinsert your Bluetooth dongle. Note: As long as your BTLE device is still advertising you should the address change to a purple color in the command prompt.
This could give you an idea of what type of functionality the device has if you have no idea how it works.
This command generates a list of all the available handles. For instance, my device has a handle to access battery level data and another to enable automatic reporting of the battery level data. Remember, a handle is a sequential number generated by Bluez which is tied to a specific characteristic.
You can use the output of char-desc to relate the characteristic UUID to each open handle. In my case, I know that the handle for reading the battery level is 0xe. The command to read a handle is as follows:.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm trying to connect to a device using gatttool on Linux. Then I type connect. I see [CON] as expected, but the problem is that it disappears automatically after about 1s, with no error messages.
I have been searching for hours, but I don't see why that is so? Note: I have run hcitool lecc before running gatttool one time just to try it, but it seems to me that since then, gatttool connection is not working properly anymore unexpected disconnection as explained above. Is it because I have used hcitool lecc? If yes, is there a way to "undo" it? Not sure if this helps you because I'm seeing this behavior on my Raspberry Pi an up-to-date wheezy version and bluez 5.
I can connect to my BLE peripheral from the command line after doing an lecc without any problems. I don't think you need to reset after an lecc. Regardless, if you do want to reset your BT dongle because it is in some funky state, look at this excellent step-by-step guide to reset the BT dongle. I have followed these steps with consistent results. I can connect and query say primary but more often than not, the connection drops before I can manually type in primary.
See the results below. Learn more. Asked 6 years, 3 months ago. Active 6 years, 1 month ago. Viewed 6k times. Richard 7, 3 3 gold badges 29 29 silver badges 42 42 bronze badges. Active Oldest Votes.