I'm working with fast Bluetooth detection and inquiry. I know a few seconds are needed to accomplish BD_ADDR and name detection while using Bluetooth 2.0 devices.
Does anybody know whether anything faster, or any kind of fast pairing or name beaconing ares expected with Bluetooth 3.0?
I found out the improvements are more on the transmission rate, once the link is established, but nothing on the inquiry / exhange of information without pairing side?
The major improvement to Inquiry (device discovery) was at v2.1 with EIR (Extended Inquiry Response). Previously only the Device Address (and CoD, IIRC) was sent in the Inquiry Response. The discoverer then had to make a ACL connection to read the remote's Device Name -- and then query its SDP database etc etc. The Extended Inquiry Response can include the Device Name along with other things -- supported Class Ids etc.
See section 7.7.38 Extended Inquiry Result Event in the HCI chapter (Vol 2, Part E), in spec v2.1 (the one I have at hand just now).
e.g.
http://library.forum.nokia.com/index.jsp?topic=/Nokia_Symbian3_Developers_Library/GUID-F2A793F1-A5B5-526B-B147-771D440B13A2.html
Related
I'm working on a project that requires BLE Serial Profile.
I have successfully implemented it, but now I'm wondering what happens when server is sending data to the client, and client wants to send data back (while server is still sending). Is this handled on the low level with a queue or something similar?
Is there any risk that messages will get lost?
Thanks for any help.
Bluetooth provides the effect of full duplex transmission through the use of time division duplex (TDD). In principle transmission and reception do not happen at the same time. So in your case there is no risk of collision (loss) of data packets.
As you can see "Central" and "Peripheral" have a window of 625us during which they transmit.
For further details you can read "Timeslot" chapter of the base band specification in Core Bluetooth specification.
https://www.bluetooth.com/specifications/specs/core-specification-5-3/
I recently aquired a Segway Ninebot ES2 electric scooter. I can connect to the scooter via Bluetooth LE and grab information such as battery status, current mileage, temperature, and so on. This is all done through an application.
On my Android device, I've successfully extraceted the HCI log file, which I imported into Wireshark. I can see all the requests and commands send back and forth between my phone and the scooter. However, the requests and responses are all garbage and I have no idea how to interpret them.
Example of a sent command (info says Sent Write Command, Handle: 0x000e (Nordic UART Service: Nordic UART Tx))
Example of the received value I got right after (info says Rcvd Handle Value Notification, Handle: 0x000b (Nordic UART Service: Nordic UART Rx))
How am I supposed to interpret these responses? If the battery status was 59%, I would expect it to return something like 0x3b (0x3b hex is 59 decimal). But honestly, I have no idea how this works. Maybe they're returning a bunch of data in a data type only their app knows how to interpret? Like JSON for web.
Here's an example from the nRF Connect for Mobile application, where I hit the down arrow on all the characteristics: https://i.imgur.com/hREDomP.jpg (large image)
And probably more important: How do I replicate a request or command in nRF Connect? I've tried sending a byte array that looks like 0x {02410011000d.....} (from the Write Command) in the application, but I have no idea how to read the response.
If someone is still interested, I did the same research for this scooter.
That's standart BLE communacation, device offers BLE "services" and "characteristics". Service can contain one or more characteristics, by which you communicate with device. Each charateristic can allow different types of interaction with it: writing into it, reading from it, subscribing to notifications (so you dont have to to manually read, it kinda pushes data to your app), and more (read here, for example)
Take a look at your wireshark screenshot: you can see Service UUID, Handle UUID (the characteristic), and handle ID. You can communicate with device via uuid or id, depending on your programming language or library (more about uuids).
In this particular scooter there are two characteristics, one allows writing into it, another - allows subscribing to it. Together, they act like RX and TX wires in UART: you write data into one and read from another. So, to begin communication with scooter you must establish connection to it, subscribe for notifications from one ch, and write data to another.
As for protocol: look again at she screenshots, "UART Tx" is the actual payload that was sent to scooter and "UART Rx" was the response. Yes, it's binary data, that only app would understand. Luckily, protocol has been reverse engineered and is well documented. In your example app requests serial number, and it's returned in response - "N2GWX...". In order to request battery percentage you must build another payload according to protocol.
I'm not sure if it's still relevant, but at least for those, who will be interested in the topic.
You can try the following to understand how to interpret response from the device.
An option to consider is to fetch manufacturer's mobile app (apk) either by adb or from sites like apkmirror, etc.
Then apply some reverse-eng tool like JADX.
If you're lucky and the code is somewhat readable, then search for smth that has to do with response (like ResponseParser) and try to find algo that is used to interpret the response.
However, the very first attemp should always be to search on github/google if smb did it already for your device, unless it's very niche.
I study the bluetooth low energy. During studying, I have a question.
As I know, possible data transaction Role is observer-broadcaster(connectionless) and central-peripheral(connection) in BLE.
But, What I wonder is data transaction between observer and peripheral?? Is that possible?? In other words, Can observer scan the peripheral's broadcasting message?
If that is possible, Can central receive the broadcaster's advertising packet? and Can central scan the broadcaster's advertising packet?
An observer can scan the advertisements from the broadcaster, unless the advertiser (broadcaster)'s advertisements are of type nonconnectable.
There are two types of scanning in Bluetooth Smart (Bluetooth Low Energy): passive and active.
Passive scanning just listens to advertisements (which contains advertisement data).
Active scanning when an advertisement is received it sends a scan request and the advertiser then sends a scan response (which contains scan response data) back.
There are different types of advertisements in Bluetooth Smart:
general advertisement: The typical advertisement whereto connections can be initiated. It supports active scanning.
direct advertisement: The advertiser wants a particular device to connect to it instantly. It does not support active scanning and does not have any advertising data (except the connection addresses of both devices).
discoverable advertisement: The advertiser supports active scanning, but can not be connected to. (i.e. broadcast of data).
nonconnectable advertisement: The advertiser does not support active scanning, and can not be connected to. (i.e broadcast of data).
I am analyzing the traffic beacons generate using tshark and iptraf. I know they are mainly used to determine the proximity of a device and like any other network device the traffic generated by them must be having a header and payload information in it.
What is best way to find out the payload information though header info can be identified as to where packet is being sent etc , but how we can classify the payload and what information it contains in a beacon signal , is it the same like any other web traffic sent and receive on a network or is it different since they make use of Bluetooth ?
Any pointers regarding would be useful .
Bluetooth LE beacon transmissions are much simpler than the HTTP protocol. They are transmit only and have no real headers, although there are short segments within the transmissions called PDUs that have a similar purpose.
To see an example of a beacon transmission, see my answer here:
What is the iBeacon Bluetooth Profile
We are testing Bluetooth in WEC2013 with a USB based dongle from generic vendor on iMx6 platform. We are using the default HCI Transport layer provided with WEC2013 BSP.
BT is turned on and able to scan all the nearby devices.
We have enabled following set of sysgen variables and registry entry.
Sysgen Variables:
SYSGEN_BTH (Bluetooth stack with universal loadable driver)
SYSGEN_BTH_BTHUTIL (Bluetooth Profile Management APIs)
SYSGEN_BTH_HID_KEYBOARD (Bluetooth HID - Keyboard)
SYSGEN_BTH_HID_MOUSE (Bluetooth HID - Mouse)
SYSGEN_BTH_AG (Bluetooth HS/HF and Audio gateway service)
SYSGEN_BTH_SETTINGS (Bluetooth settings UI)
SYSGEN_OBEX_CLIENT (Obex client)
SYSGEN_OBEX_SERVER (Obex server)
SYSGEN_OBEX_FILEBROWSER (OBEX file browser)
SYSGEN_OBEX_INBOX (OBEX Inbox)
SYSGEN_FTPD (FTP server)
SYSGEN_BTH_BTHSSVC(Support Secure Simple Pairing)
Registry entry:
[HKEY_LOCAL_MACHINE\Drivers\USB\LoadClients\Default\224_1_1\Default\Bluetooth_USB_Driver]
"DLL"="bthusb.dll"
[HKEY_LOCAL_MACHINE\Drivers\USB\LoadClients\Default\Default\224_1_1\Bluetooth_USB_Driver]
"DLL"="bthusb.dll"
[HKEY_LOCAL_MACHINE\Software\Microsoft\Bluetooth\Transports\PnP\{B3DD867A-1E6E-4215-8AA7-EAC1DFC46548}]
"flags"=dword:80000000
"driver"="bthusb.dll"
"resetdelay"=dword:0
"PacketSize"=dword:200
"BlockSize"=dword:5
[HKEY_LOCAL_MACHINE\ControlPanel\Bluetooth]
"PinAttemptInterval"=dword:200000
"PinEntries"=multi_sz:"0000","8888"
We observed different scenario's in pairing to a device.
Connecting to mobile from board(imx6+usb dongle running with WEC2013)
Here pairing is success when pair is initiated through bthsettings UI. It will trigger the 6-digit automated passkey on both the sides.
Connecting from mobile to board without opening bthsettings UI.
Here pairing is success once. When the UI is not open (BT is ON in background), pairing is initiated from mobile, both will be paired using automated
6-digit passkey method. But this will internally invoke bthsettings UI, so next time when we give pairing from mobile, mobile side will ask for manual
key insertion. As soon as the key is entered on mobile and pair is pressed, pairing rejected notification will be observed on mobile terminal.
So pairing is failed in this case.
Connecting from mobile to board when bthsettings is opened.
Here pairing is failed. When pair is initiated from mobile, manual key insertion UI will be invoked and when key is inserted and pair is pressed,
pairing rejected notification will be displayed on mobile terminal and pairing is failed.
In these failed senarios, the upper layer is responding with "Pin code request negative reply command" for "Pin code request event" from chip.
We need input on this pairing process. Why this automated key and manual key generation methods are invoked based on whether UI is open or never opened? And why manual key case is failing?
Are we missing any registry entry or stack feature ?
It all got to do with SSP(Secured Simple Pairing), which decides the pairing authentication model. This is affected in WEC8(2013) through the changes under bthsettings.
Under WEC8 they disable SSP(via function EnbaleSSP()) whenever a connection is initiated from external device and enable back SSP when conenction is initiated internally. Though this is the logic, I'm not aware of why this is introduced(and is it a bug, that'll be fixed in upcoming updates as they initially did for NDIS 5 wireless driver connection).
And as a workaround to this, disable EnableSSP().
Also SYSGEN_BTH_BTHSSVC is implicitly needed by SYSGEN_BTH_SETTINGS component, and the link is broken under WEC8.
Microsoft has provided the fix in April 2015 update. Details available here.