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Max packet size allowed for BLE communication

Richard Amaral
Prodigy 115 points
Other Parts Discussed in Thread: CC2541

Hi,

 

Does anyone know what the maximum packet size is for a BLE message? I have a need to send and receive 80 byte messages. Thanks.

 

-Rich

 

  • 0
    TI__Genius 12545 points

    80bytes user data per connection interval (limitation of our implementation)

    Min BLE spec connection interval = 7.5ms

    Max data rate   = 10640 bytes per second

    This is probably a little optimistic,  but 8-9K should be fine.

  • 0 in reply to Chatto
    Intellectual 840 points

    When you use GATT protocol (the only protocol currently available to the application layer) , the maximum user data in packet is 20 bytes (for example in write or writeNoResponse commands). 

    From tests I have made, the theoretical data rate based on calculation of 4 packets send in every connection event is not achieved in practice.

    I noticed that at low connection intervals (< 100ms) the stack usually sends 3 messages per connection event (if maximum packet size is used). 

    But as Chatto wrote, 8Kbytes/sec is achievable. 

     

  • 0 in reply to Sasha Kalmanovich
    Intellectual 310 points

    I am using modified SimpleBLEPeripheral firmware on a circuit I designed with a CC2541, and even after setting the Connection Interval parameter to its minimum value (6, for 7.5ms), I am only able to send back to back notifications with a ~65ms delay between the receipt of each notification reported by BTool using the USB Dongle from the TI Dev Kit. I am observing two things, I think:

    1) Only one notification event per interval

    2) Intervals are much longer than 7.5ms

    Do you have any ideas as to what I'm missing here? Thanks!

  • 0 in reply to Miles Guidon
    TI__Guru 57865 points

    Hi Miles,

    The (virtual) UART communication is the bottleneck, it takes up too much time which cant be fit between the connection events.

    Best Regards