1st connection is bonded authenticated encrypted link, but 2nd connection becomes not bonded unencrypted link

[snowuyl]

I use nRF Connect to connect to nRF52832 device. 1st connection is bonded authenticated encrypted link, but 2nd connection becomes not bonded unencrypted link. Why 1st and 2nd connection are different?

The following is log message of nRF52832 device.

00> <info> app: POWER_ON.
00> <debug> nrf_ble_gatt: Requesting to update ATT MTU to 185 bytes on connection 0x0.
00> <info> app: BLE_GAP_EVT_CONNECTED (1st connection)
00> <debug> app: state=1
00> <debug> nrf_ble_gatt: ATT MTU updated to 185 bytes on connection 0x0 (response).
00> <debug> app: _securityRequestHandler
00> <info> app: BLE_GAP_EVT_SEC_PARAMS_REQUEST
00> <info> app: PM_EVT_CONN_SEC_SUCCEEDED
00> <info> app: Connection secured: role: 1, conn_handle: 0x0, procedure: 1.
00> <debug> nrf_ble_gatt: Requesting to update ATT MTU to 185 bytes on connection 0x0.
00> <info> app: PM_EVT_BONDED_PEER_CONNECTED
00> <info> app: BLE_GAP_EVT_CONNECTED (2nd connection)
00> <debug> app: state=1
00> <debug> nrf_ble_gatt: ATT MTU updated to 185 bytes on connection 0x0 (response).

[snowuyl]

[Einar Thorsrud]

Hi,

That is odd. I tested now with the ANCS example form SDK 17.0.2 and nRF Connect for desktop BLE, and after bonding the link is automatically encrypted upon reconnection (as expected). Which SDK version are you using, and do you see this with the ANCS example, or only your custom firmware? If only your custom firmware, can you explain the changes you have made? Also, can you explain in detailed steps how you reproduce this?

[snowuyl]

I am using nRF5 SDK v16.0.0. I am testing my custom firmware. Which example can I reference for bonding the link is automatically encrypted upon reconnection?

[Einar Thorsrud]

Hi,

You can refer to for instance the ANCS example in SDK 16.0.0, where this should also work. Does it on your end? If not, did you by any chance restart nRF Connect Bluetooth or click "Delete Bond Information"? (Based on the log of the second screenshot it does not look like the device is known for some reason, even though I see it has the same address so it should be seen as the same device.)

[snowuyl]

Do you mean this example?

nRF5_SDK_16\examples\ble_peripheral\ble_app_ancs_c

Beside I can't see disconnect button on nRF Connect, which method do you suggest to disconnect from nRF Connect?