handling PM_CONN_SEC_ERROR_SMP_TIMEOUT

Question

Hey. In production we are logging PM error events to try to determine the root cause for some unstable connection that keep showing up. We are seeing with high occurrence error code 4353 which is the SMP timeout. This is often found when reported unstable connections or failure to start OTA DFU. 
 From the Bluetooth Core: From Nordic Info Center: #define PM_CONN_SEC_ERROR_SMP_TIMEOUT (PM_CONN_SEC_ERROR_BASE + 0x101)
/* Pairing/bonding could not start because an SMP time-out has already happened on this link.
* This means that no more pairing or bonding can happen on this link. 
* To be able to pair or bond, the link must be disconnected and then reconnected. 
* See Bluetooth Core Specification 4.2 section 3.H.3.4 (Bluetooth Core Specification).
*/ 
 Can you provide the advised strategy to recover a stable BLE link whenever this occurs? SDK: 17.0.2 SD: s140 - 7.2.0 bluetoothctl: 5.48

Edvin · Accepted Answer

So what call is it? Do you know, or doesn't it say in the report? 
 I can't really say much more than what I already did. I guess it is calling some function that returns PM_CONN_SEC_ERROR_DISCONNECT. As the description of that value says: "Pairing or encryption did not finish before the link disconnected for an unrelated reason." 
 So the devices are disconnected when this occurs, and it is not the reason for the disconnect (at least not from the nRF's side). 
 
 BR, 
 Edvin

handling PM_CONN_SEC_ERROR_SMP_TIMEOUT

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