SDK15 pm_conn_secure() doesn't bond

[Mikhail]

Hi!

After connected and get log info "Connected." I start bonding:

// Initiate bonding.
err_code = pm_conn_secure(p_ble_evt->evt.common_evt.conn_handle, false);
if (err_code != NRF_ERROR_INVALID_STATE)
{
    APP_ERROR_CHECK(err_code);
}

but there is no any success message. 

 0> <info> app: Heart Rate collector example started.
 0> <info> app: Starting scan.
 0> <info> app: Connected.
 0> <info> app: Disconnected, reason 0x8.
 0> <info> app: Starting scan.
 0> <info> app: Connected.
 0> <info> app: Disconnected, reason 0x8.
 0> <info> app: Starting scan.
 0> <info> app: Connected.
 0> <info> app: Disconnected, reason 0x8.
 0> <info> app: Starting scan.
 0> <info> app: Connected.
 0> <info> app: Disconnected, reason 0x8.
 0> <info> app: Starting scan.

Therefore nRF52 SDK15 can't to made secure bond.

Why?

[FormerMember]

Yes, you can disable MTU request in the SDK15 central by not calling sd_ble_gattc_exchange_mtu_request().

[Mikhail]

in wich case should I do it? In wich part of code.

[FormerMember]

Instead of disabling MTU exchange request in SDK 15, it is better to add support for it in your SDK 13  peripheral. If max MTU size for the SDK 13 peripheral should remain 23, you can do something like this in on_ble_evt() in main.c:

 

case BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST:
    ret_code_t err_code;
    uint16_t mtu_size_supported_by_peripheral = 23;
    
     err_code = sd_ble_gatts_exchange_mtu_reply(conn_handle, mtu_size_supported_by_peripheral);

    if (err_code != NRF_SUCCESS)
    {
        NRF_LOG_ERROR("sd_ble_gatts_exchange_mtu_reply() returned unexpected value 0x%x.",
                      err_code);
    }

 

 

[Mikhail]

Yes, I understand it that better was add MTU in the SDK13. But If we already have project on the SDK13 and don't want any change it? Is it possible to disable MTU request on central side SDK15?

[FormerMember]

Yes, the MTU exchange is initiated by the central/client when calling  sd_ble_gattc_exchange_mtu_request().  Not calling/commenting out that function will disable MTU request exchange.