ESP32 Forum

Hi @nirmal.lad, It seems I referred to some other log and made that last comment. Sorry for that, please disregard my earlier comment. Can you please provide complete logs after `make erase_flash flash monitor` again ? I could only think of reason for this error might be because you are switching off/on your phone's Bluetooth as well before reconnecting to ESP32. Can you try without changing the Bluetooth state of phone (no reboot & no turning off Bluetooth once bond is created) ? The reason is, from the Bluetooth spec (Vol 6, Part B, section 1.3.2.1) :

If the static address of a device is changed, then the address stored in
peer devices will not be valid and the ability to reconnect using the old address
will be lost.

If the `peer_id_addr` is changed then this is treated as a new device.

Hello @ESP_Prasad,

Please find the attached log file.
I have not restarted or closed BLE in mobile phone.
Please check the attached logs.
After pairing and communication done and then rebooting ESP32, the device reconnects to Mobile phone.
This time encryption change is not generated. So ESP32 doesn't attempt for R/W data on characteristics.
and Disconnects afters few seconds.

Looking forward to your response.

Hi @nirmal.lad,

I could see the encryption state changed to encrypted in your logs I don't see any issue with pairing/bonding from BLE central.

From the logs, I could see disconnection reason = 546, which is BLE_ERR_LMP_LL_RSP_TMO(LMP Response Timeout / LL Response Timeout). As you are using nRF app, you might be able to capture phone side (advertiser) logs with DEBUG verbosity. They can be helpful to debug this issue further.

Hello @ESP_Prasad,

I have attached the log from both sides i.e. ESP logs as well as nrf Connect App log.
Can you tell me that, once bonding is done, how communication occurs?
Do I need to wait for encryption change event on re-connection after bonding?
Or there is some other methods to verify secure connection.

Looking forward to your response.

Hi @nirmal.lad,

From logs, I do not see any obvious issue, except The disconnection is happening because of supervision timeout or BLE_ERR_CONN_SPVN_TMO. Now in your application code, I do not see anything after service discovery completed callback blecent_on_disc_complete , which results in connection timeout error.

Can you tell me that, once bonding is done, how communication occurs?

There won't be much difference between communication methodology. Please refer to BLE specs or belprph demo example and try to build understanding around pairing/bonding/read/write/notify etc.

Do I need to wait for encryption change event on re-connection after bonding?
Or there is some other methods to verify secure connection.

I will try to answer the query in best possible manner, but let me know if you are looking for something else. If you are accessing (read/write) any characteristic which needs link to be encrypted (e.g. `BLE_GATT_CHR_F_READ_ENC` in bleprph example), then of course you need to wait for encryption change event. But again, this will be taken care by `ble_gap_security_initiate()`, once this function returns successfully you can run your application specific scenarios (read/write/notify).

If you are planning to use both peripheral and central then I would suggest to start with `bleprph` example as it will be more intuitive exercise. Once you understand how central connects/reads/writes to characteristics then you can proceed to building central example which will essentially do what you were doing manually through scanner (nRF app).