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WL1835MOD: Random connection loss with iOS devices

Prabirendu Bishnu
Prodigy 140 points
Part Number: WL1835MOD

We are observing random Bluetooth Connection loss with iOS devices. We have not found any particular steps that lead to the issue. We managed to capture logs from the BT Chip. The error code received by the Bluetooth controller is 0x2 (HCI Transport Error).

  • 0
    Prodigy 140 points

    The glogger output is attached. The issue occured towards the end of the log.

    ConnectionLoss.zip

  • 0
    TI__Mastermind 29250 points

    Hi,

    Prabirendu Bishnu said:
    We managed to capture logs from the BT Chip. The error code received by the Bluetooth controller is 0x2 (HCI Transport Error).

    Which HCI event shows the 0x2 (HCI Transport Error) status? Among all the disconnections in this log, most are result of the remote side terminating the connection and all the rest are the result of the local host terminating the connection. I do not see any instance indicating a connection loss.

    Best regards,

    Vihang

  • 0 in reply to Vihang Parmar
    Prodigy 140 points
    We see the error code in the BT Stack log. It is quite possible that they are misinterpreting something else but the connection loss is unintentional ( The last disconnection towards the end of the log is the one we are interested in). It happened just after starting a call.
  • 0 in reply to Vihang Parmar
    Intellectual 540 points

    Hi Vihang,

    I am a colleague of Prabirendu Bishnu, and we are looking this issue together. I have some questions regarding those "unintentional" disconnections in the log that I would like to ask you. As you said, there are two kind of disconnections:

    1. #248367: Remote User Terminated Connection:
      • Why we will get HCI_Disconnection_Complete_Event right after receiving LMP_remove_eSCO_link_req? Is it a normal case?
    2.  #2236513: Connection Terminated By Local Host:
      • Our BT stack send HCI_RESET command due to HCI Transport Error, just like Prabirendu Bishnu said, it is probably a misinterpret. What do you think?

    Thanks,

    Will

  • 0 in reply to Will Liao
    TI__Mastermind 29250 points

    Will,

    Will Liao said:
    #248367: Remote User Terminated Connection:
    • Why we will get HCI_Disconnection_Complete_Event right after receiving LMP_remove_eSCO_link_req? Is it a normal case?

    The eSCO connection has a unique connection handle than the ACL connection with the same device. The #248367 HCI_Disconnection_Complete_Event shows the connection handle of the eSCO connection, which is very much in order. It is normal.

    Will Liao said:
     #2236513: Connection Terminated By Local Host:
    • Our BT stack send HCI_RESET command due to HCI Transport Error, just like Prabirendu Bishnu said, it is probably a misinterpret. What do you think?

    The HCI_Reset command will terminate all active connections from the controller. The two HCI_Disconnection_Complete_Events for each of the connection handle make sense after the HCI_Reset from the host.