How do I park a Bluetooth connection? I'm trying to communicate with dozens of Bluetooth devices, and the time to re-establish a connection is unacceptable. I've read that you can park connections, but not found anything that answers how to do this.
I know that you can park a connection if it's on the MS Bluetooth stack. There is a nice API you can use called 32feet.Net. It lets you set the socket options. Here's a quick link to the documentation. I hope it helps.
I have been creating firmware for Bluetooth modules since 2000 and can honestly say that I have never used Park nor has any customer asked for it.
My advice, as per others in this trail, keep away from it. Perhaps Hold mode is worth investigating.
Parking mode is one of connected state mode, explained in the core Bluetooth spec, right from early 1.1 or so. Please follow up with various sniff modes as well, including the newer ones such as sniff sub rating. Other than park modes, you have hold modes as well.
Unfortunately the parking mode will be removed in next Bluetooth version(Bluetooth 5).
And, the park and hold mode are seems a beautiful way to save power but in real life, due to the IOP issue, not too much device can "really" support such kind of power save mode in market. The most common used mode is sniff but this already beyond your request.
So, just forget park mode.
Once you have an Bluetooth ACL connection with a device. If your device is the master, then you can use link layer message LMP_park.
Usually you can do this from application using HCI command
HCI_Park_Mode (Connection_Handle,
Beacon_Max_Interval, Beacon_Min_Interval)
http://affon.narod.ru/BT/bluetooth_app_c9.pdf
Related
I was always wonder what would it be my first question on StackOverflow since everything I'm looking for is already asked. (Find only one similar here Bluetooth data transfer between two countries )
BACKGROUND STORY:
From when it comes I’m a fan of Nokia N-GAGE. It’s a Nokia’s phone from 2003 with dedicated games. In its heyday 2003-2007, it has single-player, multi-player via Bluetooth and using a dedicated internet service N-GAGE ARENA for compete with people all over world.
N-GAGE ARENA servers were disabled about 2008 and as far i understand It isn't even worth trying to resurrect such a infrastructure. Mainly because it requires modifying the code of each game and that's illegal.
Multiplayer mode using Bluetooth work fine, but requires opponent 5m away max.
Nokia sold 1mln copy of this phone, and still are people all over world collecting n-gage games. I have a dream, I want to reactivate the possibility of playing multiplayer with people from all over the world.
PROBLEM DESCRIPTION:
I want to use the Bluetooth multiplayer mode by extending the usual N-GAGE to N-GAGE Bluetooth connection with an additional 3 elements. Two N-GAGEs, instead of connecting directly to each other as host-join, connect via a PC / smartphone applications that communicates with the server that transmits full data sent from the game of one user to game of the opponent.
I admit that I do not have full knowledge of technical limitations. In my opinion, as a software engineer, it is theoretically possible, but I want to consult you, people more familiar with the subject. Maybe someone is working on a similar project and can comment.
WHAT DO I KNOW:
The application would have to transmit all data from the Bluetooth connection so as not to disturb the illusion of a direct connection between N-GAGEs.
The application must enable the selection of an opponent on the basis of the game. The choice itself could be made on the basis of some kind of chat in which users first define what they are playing, who’s the host, and then the connection is made.
WHAT DO I WANT TO KNOW:
Does what I describe is even possible?
Is such capturing Bluetooth connection and forwarding is even possible?
Does the development of technology in these 15 years allow me to transfer Bluetooth connection real time through 2 additional devices and Internet connection?
I WOULD BE GREATFUL FOR:
Any technical tips, literature that can help me to understand my limitations.
Any constructive criticism. Of course before I start doing such a project I have to confirm that isn't a utopia. For me It’s a side project, I’m able to spend years on it, but don’t want to get to dead end after all effort.
Does what I describe is even possible?
Yes, yes it does. Your hardest part will be setting up a tranceiver to interpret the I/O. Your failure point would be super-encrypted messages and making transmission difficult...
If it's clear I/O you can signal this through any server and output it back to the tranciever to output. Confusing but possible just not sure of the design or how bluetooth sends its data.
Is such capturing Bluetooth connection and forwarding is even possible?
If a connection is possible then forwarding it is too. Considering this piping the transports.
Does the development of technology in these 15 years allow me to transfer Bluetooth connection real time through 2 additional devices and Internet connection?
Bluetooth real-time no... with added network latency, you're looking at anything from 1-200ms~. you may be able to improve it?
Overall I think if you can:
Connect the device to PC, and have PC talk back to device through blue-tooth
Read the data that goes in and out
Encryption proves little or none at all to be able to signal the data properly, tricky to explain you'll know though if there's a wall.
All should be possible it doesn't overly go against the grains but do more homework this is very valid.
As I understand it, Bluetooth Low Energy communication can be established with or without pairing. This is in the context of mobile development, Android more specifically but I believe iOS is more or less the same.
Are there instances where one would choose one over the other? And what would be the purpose? What is technically considered paired communication and what is considered unpaired communication?
I've dabbled around for a bit on the differences and have even made a few demo only apps related to BLE but I haven't found a clear explanation if what I am doing is actually considered paired or not.
Edit:
The reason I ask the question is that I believe I am looking to encrypt unpaired BLE connections. In some cases, and essentially my main use case, a mobile device may want to connect to several different peripherals randomly at different times throughout the day and the process of physically accepting a pair request seems unnecessary and quite time consuming. By 'randomly' I mean I am walking by one if I have a dozen scattered around my apartment and I personally don't know exactly which one without physically checking. I don't what to walk in the room the first time and have to manually pair each device, that would be insane if I had 100 devices. Note that these devices don't necessarily have to be connected at the same time, but could. Also note that I understand this isn't generally the main use case of the typical peripheral to mobile use case.
Here are a few differences:
If you bond the devices, the link will become encrypted, so it becomes more secure. So "paired" communication basically means the link is encrypted plus the device "knows" what it talks to.
The remote device also learns your phone's IRK (identity resolving key), which can be used to identify the phone later on. By default, the phone rotates the Bluetooth Device Address every 15 minutes or so. Without knowing the IRK, the peripheral can't identify the phone.
A good thing if the devices are bonded, is that the GATT db of the remote device gets cached, which means upon next connection, you don't have to wait a long time for service discovery to complete.
On Android, connecting by Bluetooth Device Address without first scanning is broken since the API lacks the "address type" bit (public/random address). If Android "guesses" wrong, you will connect to the wrong device and therefore fail. However if devices are bonded, the address type is stored and looked up based upon Bluetooth Device Address, which makes it work as expected. So if you plan to automatically connect to your peripherals in the background upon boot for example, it's a good idea to bond the devices.
A small detail is that Client Characteristic Configuration Descriptor values should also be stored by the GATT server and restored once the bonded device reconnects so it doesn't have to rewrite the descriptor value.
Some Bluetooth profiles needs bonding, for example HID (at least on iOS and Android).
I'm working on a project to track delivery trucks leaving and returning to the office.
While I know RFID would work, we're also looking at BlueTooth with mobile apps. Ideally, once a driver installs the app, we register a unique ID for the device, and a BT reader identifies when phones/deliveries leave and enter range without any user interaction.
From the Android 6.0 release notes, it looks like the MAC address is hidden from apps and BT broadcasting. https://developer.android.com/about/versions/marshmallow/android-6.0-changes#behavior-hardware-id
User management of app installs and enabling BT aside, is this feasible?
Can someone point me in the right direction to confirm what identifiers are available?
When I understand you correctly you actually do not want to track where a phone is but want to know if a person/truck/phone passes a kind of checkpoint or gate?
For newer smart phones you cannot rely on the visible MAC. Bluetooth classic is usually not visible and the BLE MAC is randomized as long as the device is not paired and bonded.
Indeed as PaulW11 stated, the simple way would be to implement an app which does BLE advertising with short advertising interval. Inside this advertisment you can put some custom data. This will be visible to everyone. This ID can be some random number, a number assigned by you or whatever.
At the gate you would implement a BLE scanner grabbing all advertisments near to it.
This should be easy to implement.
I would also like to mention the drawbacks here: If someone passes the gate you may miss him. BLE with Android is always tricky and you might have the situation that the bluetooth subsystem on a phone may have stopped working or so.
One the other hand if someone comes accidently near to your gate, you will think he left or returned. Near can be something around 50 m or so with good conditions or only 10 in other cases.
And even worse: If someone stays 'nearly' in the range of the gate you will see im sporadically. This may confuse your come and go logic if he is visible every 3 minutes or so...
This is my first question in Stackoverflow :)
I'm trying to make few modifications to the Ti Sensortag but I have few questions please:
1- is it possible to make the sensortags communicate with each-other without a gateway?
(lets Say I put Sensor1 in bedroom 1 and sensor 2 in bedroom 2 can I make them exchange readings without the need for a gateway?)
2- can I install a micro USB over the interface connector to be able to use a portable battery pack? (photo of the interface connector)
thanks
You'll get better more in depth responses on the TI support forums as Ifor has said.
However, I can tell you the answer to #1... Regular bluetooth allows for things like piconets, but Low Energy does not. With LE you have a client/server (master/slave) connection between two devices only. It may be possible to modify the firmware on the sensortags to allow them to make connections to other sensortags, but then they'd have to give up whatever connection they currently had to do so. The master devices can connect to multiple slave devices, but the slave device can only be connected to one master.
As the sensortags are currently designed, I think they only work as a slave (server) device.
Press releases say that the new 4.1 spec allows for a single BLE device to act in both roles--central and peripheral eliminating the need for a gateway. A 4.1 update is, in theory, possible with 4.0 radio hardware like the SensorTag has. I personally haven't seen an example of this however and SensorTag processing resources may be a limiting factor to a dual role.
The Battery Pack connector breaks out VDD_EXT and GND and the SensorTag hardware schematic is available. Analysis by a hardware design engineer should be able to determine the suitability of a USB source powering option.
http://processors.wiki.ti.com/index.php/SensorTag_User_Guide
Is it possible to make a computer behave as a bluetooth HID device? That is, given a local machine with a standard USB keyboard plugged into it, other devices could discover this machine and use it as a bluetooth keyboard.
I'd like to create a linux or OS X application (or use an existing one, though I've found none) which can behave as described above, but I'm not sure where to start, or if it's even possible.
So:
Is what I'm describing possible?
Are there any existing applications that do what I describe?
If no application already exists (I'm assuming not), are there bluetooth libraries or bindings that will help? (I'm pretty comfortable using most of today's popular languages, so I'd prefer a library most directly suited to the task, so long as it's available in linux or OS X.)
Failing any of the above, the bluetooth spec looks pretty dense. Are there specific guides or other starting points applicable to the problem at hand that I can read?
I realize that such an application would most likely need to steal the normal keyboard input, possibly providing some KVM-like hotkey for switching between providing input to the host operating system and sending the input over bluetooth to the connected device, but I'm considering that problem to be outside the scope of this question.
It is definitely possible on Linux. Some time ago I found this project:
http://nohands.sourceforge.net/index.html
They emulate a full-blown headset with audio and keyboard controls on the Linux bluetooth stack. If they can emulate something like that, you would probably be able to emulate something simpler like a keyboard.
It is possible, however I don't think I'll be able explain it very well and I don't know the entire answer. A BT HID device works as a server and waits for connections to come to it. In linux, using the bluez stack, first you would have to advertise the HID service for other devices to see. I think you do that using the sdp.h and sdp-lib.h header files(the second header maybe called something else, I'm on a windows computer and can't check). So you would have to add the HID service record to you computer for other devices to see it. You would have to create a program that first adds this service to the record, then waits for other devices to connect, then handle the pairing process, Bluez might handle this for you, or you might have to do some things to it, I'm not quite sure. You should also read the Bluetooth HID Spec found at the http://www.bluetooth.com/English/Technology/Building/Pages/Specification.aspx site. This document contains the details of the SDP record relevant to HID. Also the book Bluetooth essentials for programmers is pretty good to introduce you into bluetooth programming
I would like to have given a more concise answer, with more detail, but that's all I know ATM. I am also trying do something similar, but spare time is so hard to find ;) I'm also not on my Linux box and can't check all the details. If your are still interested, let me know and i'll try to expand my answer.
I don't know if this is helpful, nor if it is still alive and working, but perhaps you could try this link.
Another one that might or might not be helpful in some way is remuco, but I don't know if they are using a Bluetooth HID profile.
It is indeed entirely possible with Linux and Bluez. See: https://github.com/lkundrak/virtkbd/blob/master/btkbdd.pod
Try Across, unfortuantly for me my phone was lacking support.