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Wearable BLE devices, 3 slave limitation

Uri Kluk
Prodigy 70 points

Other Parts Discussed in Thread: CC2540, CC2570, CC2571, CC2564, CC2567

Hello,

What profile should I use if I want a group of transient devices to join a master and react for an event?

Example: 10 people wearing BLE hats walk to the same area and when someone press a button the hats get signal to flash LEDs .

In this case the button is the master and the hats are the slaves.

There is no confirmation needed, so Broadcast works fine.

Am I constrained to only 3 slave devices in broadcaster mode? How can I word around it?

 

  • 0
    TI__Mastermind 25035 points

    Hi Uri,

    Our CC256x dual mode device supports up to 6 simultaneous BLE connections(10 in the future). I believe you are using the CC2540, so I will move this thread to the appropriate forum.

     

  • 0
    Intellectual 550 points

    Hi,

    Just a quick suggestion, if your system does not require BLE, I would suggest ANT can do this use case quickly with minimal overhead, and is available on the CC2570, CC2571, CC2564, and CC2567. An ANT shared channel enables up to 65535 devices to slave to a single ANT master channel, or an ANT Continuous Scanning Mode node can receive from up to 600 ANT Master transmitters simultaneously.

    So in this case you could implement the ANT+ Controllable Device Profile on your hats, and then use an ANT continuous scanning mode device to control up to 50 hats, or if you didn't mind a more closed ecosystem, you could make a remote which broadcasts a channel which all of the hats "slave" to and then just send a message from the remote which controls all of the hats (a shared channel also keeps both ends of the link low power).

    http://www.thisisant.com/resources/ant-message-protocol-and-usage/

    http://www.thisisant.com/resources/an07-auto-shared-channel-master-example/

    http://www.thisisant.com/resources/an14-continuous-scanning-mode/

    Cheers

  • 0 in reply to Harrison
    Prodigy 70 points

    Thx for the post,

    I acknowledge that I have no experience yet with the protocol or the SoC features, but want to know if I am looking at the right tool for the task.

    BLE is a requirement; The goal is to flash all the BLE clients in proximity from a Smartphone master when a particular event occurs.

    If broadcast only supports 3 clients, then is it possible for the master to unicast the message to the 50 clients fast (sub-second)? what bluetooth profile/service?

    Does the master need to pair and send data to each client in this unicast suggested approach, or is it possible to "remember" the pairing information (Just as a sample, if this was Wi-Fi, once the pre-shared key is know the only task is to authenticate and encrypt the messages, but no need to provision).

     

  • 0 in reply to Uri Kluk
    Guru 22270 points

    Hello Uri,

    If your smartphone or device is iOS and if the BLE devices will be known then a possible solution would be to name them sequentially.

    In your BLEDiscoveredPeripheral you would record all the devices myBLEClient[x] and then send the information to each one.  Or simply loop through them, connecting 3 at a time on the iOS.

    I know the pairing information is stored, so you can create a whitelist of clients.  This is something I have not attempted, but should be a workable solution if the clients or location will change.

    Thanks,

  • 0 in reply to Greenja
    Expert 1290 points

    you said that a confirmation is not necessary?

    if the available power on the hats is not to limited you could implement the heads as central devices which simply scan for ADV-broadcast packets.

    the event notification could then be done by simply broadcasting an appropriate ADV-packet from the smartphone.

    can anybody with BLA-on-apple-knowledge confirm that an iDevice can act as peripheral/broadcaster?

    just my 2ct...

  • 0 in reply to Andre S
    Prodigy 70 points

    Andre,

    That sounds like a great suggestion, but can any BLE device scan for ADV-broadcast packets, or only paired devices?

    To test, do you know if I can set the EK with CC2540 to act as peripheral/broadcaster? I worry about the smartphone later.

    Best regards!

  • 0 in reply to Uri Kluk
    Expert 1290 points

    Hi Uri,

    As far as I know broadcasts are not different from other ADV packets. And because the ADV packets are for device discovery every central can receive them, no pairing involved. It wouldn't work with non connectable devices if it were otherwise.

    you should be able to make the USB dongle advertize by using BTool. Take a look at the HCI documentation, especially the GAP_UpdateAdvertisingData and GAP_MakeDiscoverable found in the "Adv. Commands" tab in BTool.

    Good luck

    Andre