I'm developing a stereo headset with Bluetooth using the classic profiles (HFP, A2DP, AVRCP) as one would expect Ina stereo headset. However, I want to deploy a remote control app for iOS, and use it simultaneously to the other classic links, but the dual-mode chipset I'm working with in my design does not behave as I'd expect;
The headset is setup as a peripheral, letting the iOS device act as central. As such, the peripheral advertise its BLE services (with my specific 128-bit UUIDs) and all is good. I can browse the peripheral from any central, but only when I'm not connected with classic profiles (e.g., while not streaming audio).
My device does not seem to be able to advertise BLE, while connected with HFP and/or A2DP! However, I have seen demos of the same chipset acting as BLE central, scanning and connecting to other BLE peripherals, while simultaneously streaming audio via A2DP. However, in that setup the device was acting as A2DP sink connected to an iPhone, while scanning/connecting via BLE to a third unit acting as BLE peripheral. Hence, not point-to-point with both Classic and Smart Bluetooth to the same device.
Is there a dual-mode constraint that one cannot act as peripheral while supporting/connecting to Bluetooth Classic profiles? And that only Central-mode is supported in that case?
FYI, I'm using CSR's 8670 chipset.
UPDATE
New answer added. My apologies for not clarifying/cleaning-up my previous answer until now -- time flies!
Well, after digging down into specs and trying to understand things more clearly, I've found the answers I was looking for, even though I would have preferred to more optimistic answers... ;(
Nevertheless, let's get to it; the Bluetooth spec for 4.0 (BLE) says that;
Dual-mode gadgets cannot act as BLE peripheral and advertise its
presence while still being connectable in "Classic" Bluetooth using
BR/EDR.
Furthermore, CSR source-code examples for the CSR8670 dual-mode chipset I'm using all behave in the same say; BLE advertisements as peripheral are disabled when any classic BT-link is connected. Instead, the CSR source code promote that the device should act as the BLE central instead, allowing other BLE peripheral units to advertise and connect to it, all fully doable while streaming audio (acting as A2DP sink).
This does not suite my setup at all since;
BLE centrals consume more power than BLE peripherals, and my device needs to conserve energy
The dual-mode "combo"-problem of combining a BR/EDR-device with BLE peripheral functionality just moved to the phone instead, which will not work any better since we cannot expect Apple (or anyone else) to violate the BLE spec.
Instead, the recommended approach is let my stereo headset skip BLE entirely and use GATT over BR/EDR instead, also known as advertising via "vanilla", which makes sense really; I mean, I already have an ACL-link setup between two devices, why should I need to kick any sort of discovery mechanism?
Again, the Bluetooth SIG comes in handy;
https://developer.bluetooth.org/TechnologyOverview/Pages/GATT.aspx
GATT and ATT are not transport specific and can be used in both BR/EDR
and LE. However, GATT and ATT are mandatory to implement in LE since
it is used for discovering services
So, the SIG says "yes" to using BR/EDR as transport for GATT, but the question then instead becomes; how can I then get access to that connected BR/EDR device from within my iOS-app, where the typical scenario is to use CBCentral to scan, discover and connect to a CBPeripheral? The answer is simple; you cannot, since iOS 7.0 does not (yet?) support GATT for BR/EDR;
https://www.bluetooth.org/tpg/showDeclaration.cfm?3A000A5A005C5344535D5414403B0C0D0E2405022413010E57503F202A5A72
So, to sum things up; if you want to have a peer-to-peer setup between two dual-mode Bluetooth devices, using BOTH Bluetooth Classic profiles AND Bluetooth Smart services/characteristics, you should use GATT over BR/EDR, which is no-go for Apple-devices, but might be supported by Android (don't know, will port app to Android eventually though, but regardless it's not a big deal for Android since worst-case will imply a fallback to SPP and a simple byte-protocol to do the work that I need to get done).
That's that. Hope that I've helped someone ;)
/Markus
You learn as long as you live, I suppose, and this question's answer is NOT that it's not supported which I claimed earlier (based on what I thought I knew).
The short and clean answer to dual-mode and headset development on CSR-chipsets is simply that it was a constraint in the CSR bluetooth stack on earlier SDKs.
The Bluetooth SIG has never not supported dual-mode acting as Peripheral while being connected via classic links to the same device. On the contrary, it clearly spec. how such interoperability should be carried out -- but that doesn't always mean that all BT-stack implementations out there are capable of such functionality.
Hence; Using the latest devtools and the latest Bluetooth firmwares/stacks from CSR has resolved all issues and dual-mode is now fully, and actually quite nicely I might add, supported on the CSR8670/75 chipsets.
I am also using the CSR8670 device.
It have it working. Both a BLE peripheral and audio.
You need to be using ADK 4.0.0 by CSR.
Bluetooth 4.1 and Bluetooth 4.0 are different. For what you said about Bluetooth 4.0 is correct, but your chip can do Bluetooth 4.1.
4.1 allows such connections.
I also added "Dual mode" flags to the advertising packet.
There are a few conditions, such as a connection Interval of at least 90 miliseconds highly recommended so you dont mess with the audio.
Good luck!
Related
UPDATE: please, keep in mind that since iOS 13, CoreBluetooth now supports both BLE and classic Bluetooth devices.
From Apple:
This year, we've merged the two layers together, and now, you have
transparent access to both BR/EDR and low energy without doing
anything. Now, what this means for you is without much changes in the
API, you can now work with both the classic devices and the low energy
devices.
[...]
This now will allow transparent use of GATT with the BR/EDR devices.
It's still running the exact same Bluetooth SIG protocol. There's no
changes to that, and so you can look at this specification online on
the Bluetooth SIG website. To your application and to the developer,
the CBPeripheral APIs are exactly the same. You can still do the same
service discovery and be notified of changes to characteristics.
Note: BR/EDR refers to the radio technology of the Bluetooth specification before the 4.0, used for LE devices. More info here.
I am trying to scan for some Bluetooth devices using CoreBluetooth but I am having trouble to discover them.
I am using Apple's sample code from this talk as reference.
This is how the Central Manager is initialized:
let cbManager = CBCentralManager(delegate: self, queue: nil)
This is how I'm scanning for peripherals:
cbManager.scanForPeripherals(withServices: nil, options: [CBCentralManagerScanOptionAllowDuplicatesKey: true])
Since I don't know the serviceUUID to which I should connect initially, I am scanning with nil as the list of CBUUID.
When peripherals are discovered, then I get notified via the centralManager(_:didDiscover:advertisementData:rssi:) method of the CBCentralManagerDelegate and I hold on to those peripherals, which allows me to discover services on them via the peripheral(_:didDiscoverServices:) method of the CBPeripheralDelegate.
Having discovered a peripheral, and having discovered its services, I can connect directly to that peripheral next time with:
cbManager.scanForPeripherals(withServices: [myDiscoveredService], options: nil)
So far, so good.
However, I can't even seem to get started with devices which are not discovered. This is happening for a number of devices that do show up in the Bluetooth settings app.
How can I get exposed to those devices, which are clearly visible to the device but I can't get to discover from the code?
Would it help if I knew the serviceUUID to begin with? How can I get such serviceUUID by other means, possibly with additional tools?
Things I tried that did not work:
use the Bluetooth explorer from the new Xcode 11 additional tools to get information about the device: though I can get a fair amount of information about the target Bluetooth devices (via "Show Device Discovery", then "Get device info..."), I can't seem to find a suitable service UUID
use the Packet Logger for live capture of the iOS trace while scanning (from the same additional tools package): I see HCI Packets and HCI Events but I can't seem to figure out any valuable information from that traffic
I'm using iOS 13.2 and Xcode 11.2
CoreBluetooth now supports both BLE and classic Bluetooth devices.
This is a misunderstanding of the new features. As the quoted text notes, "This now will allow transparent use of GATT with the BR/EDR devices." (emphasis added)
GATT over BR/EDR is not a particularly common feature in Bluetooth devices, and has nothing to do with audio streaming devices. Other profiles such as A2DP, HID, and HFP, are still not supported by Core Bluetooth. These are likely the profiles supported by the devices you're working with.
For those of us who design Bluetooth products, this new feature is really quite powerful and exciting, but we need to update our firmware to support it. It's not something you get for free on the hardware side.
I am writing an app for iOS that needs to receive data from a Bluetooth device (classic Bluetooth, not BLE). I need a pretty fast data transfer, 1Mbit/s or faster if possible. This already works using SPP in Android.
Apple only supports some Bluetooth profiles as listed here: https://support.apple.com/en-us/HT204387 I think these profiles are the only ones supported without being in the MFi program. MFi is too difficult to deal with so I would really like to avoid it. SPP is of course not available.
Of these profiles, PAN and maybe A2DP and HFP seem likely to be usable for bulk data transfer. A2DP or HFP would be a hack as they are really not designed for non-audio data. This seems to leave PAN.
How can an iOS app transfer data from a classic Bluetooth device using PAN? I would like the app to connect and somehow establish a data connection. This may be over IP (like tethering or reverse tethering using PAN) or non-IP. I want something which behaves a lot like the SPP profile, in other words a bidirectional serial link between the two sides.
Note: The Bluetooth device on the other side of this can do anything that is needed (I am writing the device firmware at the same time using a bluetooth stack, probably the TI dual-mode stack). Extra bounty if you can give me example of PAN tethering using any Bluetooth stack (TI, Synergy, dotstack etc).
See also: Is possible to communicate via Bluetooth PAN in iOS with tethered devices
I have a idea that requires connecting an ios device to a Raspberry Pi without the end user having to do anything special. The device will not be connected to an existing wifi network so BT or wifi hotspot seem to be my only options, BT preferred.
I'm aware that Apple does require some sort of BT hardware approval which I wont have I'll be using generic BT hardware. Once a connection is established I then want to be able to request data or call API's running on the Raspberry PI.
Does any of this sound achievable and are there any links that may help.
There are two flavours of Bluetooth: the so-called Bluetooth Classic, and the newer Bluetooth Low Energy (also called Smart Bluetooth or Bluetooth 4.0, though this is actually incorrect as BT 4.0 includes both Classic and Low Energy).
On iOS, Bluetooth Classic devices do indeed need to go through specific processes (MFi), or use an existing BT protocol supported by iOS to be used.
However, you can connect to any Bluetooth Low Energy (BLE) device, without any need for MFi, approval, or support by iOS. This is done though the Core Bluetooth framework.
As long as Bluetooth is enable in the iDevice, you can connect to a BLE device without any user interaction (though UX usually dictates doing so, so a user can actually select a specific device if there are many "matching" devices in range).
I have a specific requirement to communicate an iOS device with a wifi/bluetooth enabled device. At this moment, I'm confused with some points and requires an expert advice.
Can I use adhoc wifi method for communicating? but in this case, can I connect to another network? On my research, I found no so I'm opting for Bluetooth.
If I go in bluetooth communication,
Do the device need MFI licensing or can we use classic bluetooth?
From few blogs I found out that Bluetooth low enrgy devices with 4.0 can be used to communicate with ios without licensing. Will this work?
PS: My requirement is to send strings of data to and fro from the ios and other wifi/bluettoth enabled devices.
An iOS device can only be connected to a single Wi Fi network at a time, so an Ad-hoc network connection probably won't work for you.
If you join the MFi program you can use the Wireless Accessory Configuration (WAC) feature to simply the process of connecting your device to the user's existing network.
If you use Bluetooth Low Energy/Bluetooth Smart/Bluetooth 4.0 then you don't need to go through the MFi program, but you are limited to iPhone 4S and later and iPad 3 and later. If you use "classic Bluetooth" (Say Bluetooth 2.1 Serial Port Protocol) then it will work with all devices but you need to go through MFi.
Bluetooth Low Energy isn't great for high data volumes (say video streaming) but is fine for smaller amounts of data (you talk about "strings" so it will probably be suitable for you).
The other advantage of BLE is that it is independent of the iOS device's Internet connection so the user can cary the BLE device around and maintain communication regardless of their WiFi connection.
Can you pair a bluetooth LE device in an iOS app, i.e. not via Settings. Trying to make it easier on the user to pair with a specific device.
If so how?
You don't pair Bluetooth LE devices through system settings. Generally you don't pair with Bluetooth Low Energy devices at all. The only time that pairing is required is when the device has an attribute that is marked as encryption required - attempting to read this attribute will trigger a pairing process, but before you can read you need to discover and connect to the device.
Discovery and connection is handled by the Core-Bluetooth framework.
The Core Bluetooth Programming Guide goes through the steps required to use a CBCentralManager to discover and connect to a BLE peripheral.
According to the BT SIG Security Manager documentation you can pair/Bond ble devices if they respond to the message that is.
You can also wait and do it as previously explained from the peripheral side. Some devices like HipKey does this automatically when connecting first time.
Look at BTSIG Security Manager specifications.
On Android this also works from BT settings menu IF the peripheral supports it.
Bonding and Authenticating are usually confused but om most platforms it means the same.
A good way to try this out is by buying the TI ble development kit. Its cheap. It comes with a USB dongle and SW which can be used to initiate pairing like from the settings menu.
To do it from iOS just connect and read a known encrypted characteristic.
Cases where you want to "pair" (remember a Bond) includes Pulse meters, hearing aid, keyboard and other private units.