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Connection interval & Energy (Fixed Packet payload)

Wayne Chen76
Prodigy 110 points


Hi all~

I want to ask about the energy consumption with different connection interval.

If our packet load is 1kbytes, and then we adjust the connection interval from 7.5ms to 1s.

We calculate the transmission time is  (1kbytes/event_payload)*connection interval, so energy is (transmission time)*current*voltage.

I want to know that is the small connection interval would lead to the higher current and the energy consumption would be higher?

So is there any equation about the current & connection interval?

THKs~

  • 0
    TI__Genius 17975 points
    If you are sending GATT notifications, the max payload you can have is 20 bytes. It is not possible to have a 1kbyte payload. It would need to be split between packets. It is more efficient to send multiple packets per event. Our overlapped processing feature can help you to maximize this. More information on that can be found here: http://processors.wiki.ti.com/index.php/OverlappedProcessing
  • 0 in reply to Willis1
    Prodigy 110 points
    Ya~ My event payload is 20bytes. So if I send 1kbytes, it may split to 50 events. But I want to know that is the connection interval would raise up the transmission current? (1kbytes is my example)
  • 0 in reply to Wayne Chen76
    Genius 4470 points

    Yes, BLE consumes more power during connection events i.e. data transfer. You can control the transmission power by setting various supported values in TXPOWER register, but please note that it will affect the BLE range.

  • 0 in reply to Dhaval V
    Prodigy 110 points
    Thks for reply. So the connection interval would lead to different energy consumption for the fixed packet load?
    Example, (7.5ms interval for 1kbytes) & (1s interval for 1kbytes) would be different energy consumption?
  • 0 in reply to Wayne Chen76
    TI__Expert 6505 points
    Actually, in BLE each packet can be 20 bytes, but you may be able to send more packets(6 I think) in one connection event. Each connection event consumes more power than sleep, but even if you were to send a big packet of 1 kbps( not allowed in BLE spec), you may end up consuming more power than small multiple packets as the energy required to re calibrate the radio(due to heating up of radio while transmitting very large packets) can be very high.

    Anyway please have a look at Overlapped processing to understand how you may be able to send data faster.

    Regards,
    Arun
  • 0 in reply to Wayne Chen76
    TI__Expert 6505 points
    Well, having a 7.5ms connection Interval means, you will have 133 Connection Events in a second and you would be transferring data for only 50 events and rest are idle(empty) events. So your Average power consumption would be higher compared to lets say 10 connection events (100 ms Connection interval) with each connection event transferring 100 bytes( 5 packets of information in one connection event) in one second.

    Regards,
    Arun
  • 0 in reply to Arun Menon
    Prodigy 110 points
    Thank you.
    I do the experiment in the CC2540EM board and I adjust the connection interval by osal_start_timerEx function. I found the peak current would be different in different conneciton interval so I ask this question. My code is similar to the "Overlapped processing" and adjust the "SBP_PERIODIC_EVT_PERIOD" parameter to be the connection interval.