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Questions about data packets with notification captured by packet sniffer.

user4616934
Intellectual 675 points

The picture captured is as belows,

please see packet no. 1676-1678, why did not slave device response master for 3 times? There are 3 time frequency hopping to consuming more time, is it caused by channel interference? it is ok from master to slave, there is problem from slave to master. Why do not BLE stack select the good channel on which both directions communication are no problem quickly?  

  • 0
    TI__Genius 13620 points
    It can either be the slave not sending the response to the master or the sniffer not receiving the package. From the log, the master sends one empty packet (#1676), then another (#1677) and then a retry (#1678) which the slave reponds to. Given the values of NESN and SN, it might seem like it is the sniffer that loses the packet. What's the signal strength of the slave? Is it far away from the sniffer?
    The BLE stack can modify the hopping pattern and omit channels if there are problems with one of them. You could post a question on the BLE forum to get more insight into how that works. But the stack won't adjust immediately, and there will always be lost packets in an RF link.
  • 0 in reply to M
    Intellectual 675 points
    Thank M a lot, my slave is set 4DBm for Tx power and set HIGH for Rx gain, PCB antenna is designed in my slave, same as meadered IFA in TI USB dongle reference design
    HCI_EXT_SetTxPowerCmd(HCI_EXT_TX_POWER_4_DBM)
    HCI_EXT_SetRxGainCmd(HCI_EXT_RX_GAIN_HIGH)
    HCI_EXT_TX_POWER_4_DBM and HCI_EXT_RX_GAIN_HIGH are defined in hci.h
    My sniffer board is very closed to slave and central.