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Broadcast support in Bluetooth

John J Wu
Genius 3870 points


Hi, is broadcast supported in standard Bluetooth 2.1? Can the master in the piconet broadcast a message to all upto 7 devices connected? Can the end device send a message to all other devices including the master in the piconet?

Thanks,

John

  • 0
    TI__Guru 71526 points

    Hi John,

      Your inquiry is about the BT2.1 Standard, not a device type.  The CC2560-PAN1325 conforms to BT2.1: http://www.ti.com/product/cc2560-pan1315 , so we'll have to explore the sample code and the wiki: http://processors.wiki.ti.com/index.php/CC256x .   If BT2.1 supports BROADCAST, then the BT-Stack will certainly implement this as it is part of the standard.

    As well, the Bluetooth Apps E2E: http://e2e.ti.com/support/low_power_rf/f/660.aspx .  We'll have to explore this for specific BROADCAST info, I invite you to also search.

    -Leonard  

     

  • 0 in reply to LeonardEllis
    Genius 3870 points

    Leonard, Naser told me that the Stonestreet One stack does not support Broadcast. My question to you is, if Broadcast is part of the BT 2.1 standard. Would you please tell?

     

    Thanks,

    John

  • 0 in reply to John J Wu
    TI__Guru 71526 points

    Hi John,

      From what I have been able to discern from the BT2.1 spec, a master Bluetooth device can communicate with a maximum of seven devices in a piconet, though not all devices reach this maximum.  I would be concerned about using this since there is no ACK/feedback that any or all of the 'slaves' received the transmission.

    From the BT2.1 SPEC (and you can download it here: https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=241363  ):

    From Section 1 GEN DESC page 229/1420: One Bluetooth device acts as the master of the piconet, whereas the other device(s) act as slave(s). Up to seven slaves can be active in the piconet.

    From Section 3.1.3 page 104/1420: Broadcast links have no feedback route, and are unable to use the ARQ scheme (although the receiver is still able to detect errors in received packets.) Instead each packet is transmitted several times in the hope that the receiver is able to receive at least one of the copies successfully. Despite this approach there are still no guarantees of successful receipt, and so these links are considered unreliable. 

    From Section 3.3.1.2 page 108/1420:  On a broadcast logical transport no slaves are allowed to respond.

    From Section 3.5.1 page 116/1420 :  • Broadcast links. Broadcast links exist between one source device and zero or more receiver devices. Traffic is unidirectional, i e only sent from the source devices to the receiver devices. Broadcast links are connectionless, meaning that there is no procedure to create these links, and data may be sent over them at any time. Broadcast links are unreliable, and there is no guarantee that the data will be received.

    From Section 4.2 page 261/1420:  Each slave active in a piconet is assigned a primary 3-bit logical transport address (LT_ADDR). << to me, this implies a MAX of 8 addresses in the piconet, perhaps 000 is excluded, therefore, seven devices MAX.

    From Section 4.6 Page 268/1420: > read the entire section.

    From 7.6.5 Broadcast packets: Broadcast packets are packets transmitted by the master to all the slaves simultaneously (see Section 8.6.4) If multiple hop sequences are being used each transmission may only be received by some of the slaves. In this case the master shall repeat the transmission on each hop sequence. A broadcast packet shall be indicated by the all-zero LT_ADDR (note; the FHS packet and the extended inquiry response packet are the only packets which may have an all-zero LT_ADDR but are not broadcast packets). Broadcast packets shall not be acknowledged (at least not at the LC level).

    From Section 8.6 page 331/1420: 8.6 ACTIVE MODE In the active mode, both master and slave actively participate on the channel.  Up to seven slaves may be in the active mode at any given time.

     

  • 0 in reply to LeonardEllis
    TI__Mastermind 23565 points

    Dear All,

                    The CC256x does not support the Broadcast mode. Which BT profile are you planning on using?

                     FYI. the CC256x PICs are listed in the following link: https://www.bluetooth.org/tpg/showCorePICS.cfm?3A000A5A005C5345535B5314403B0C0D0E2405022413010E57503F202A5A7654514056

    Regards,

    Miguel

  • 0 in reply to Miguel
    Genius 3870 points

    Customer does not have specific profile yet. He wants to use standard BT device to handle broadcast, but the standard BT does not seem to support Broadcast.

  • 0 in reply to John J Wu
    TI__Mastermind 25035 points

    Hi John,

    Since our device does not do broadcast using classic BT, you can still use BLE feature in our device to broadcast data.