How can I bond with central device only one time?

[tianfei00]

Hi,

     This is my first time to use Nordic product and I have used nRF52832 based SDK 12.0 and SoftDevice132 v2.0 about 2 months. And the IDE used for devlopment is KEIL MDK.

In my project, I do paring operation configured with static passkey and enable bond. The problem is that after every time I reset nRF52832, my smart phone using andriod system will be asked to input static passkey again when want to connect the nRF52832.

And I used 5 days to search research usefully referrence document in Chinnese website,unfortunately I can not find any useful informations about the problem in China. So,finally I can not solve the problem by self.

I do not know the detailed operations about how to paire and bond with a BLE central device like a smart phone using andriod system only one time until now, even if nRF52832 will be reset we do not need to do bonding operations again.

So, I think I need your useful help to guide me the forever bond operations step by step, as more detailed as possible, when a project need security connectivity like paire operations.

Thanks & Cheers.

The following is my key code about the configure paire and bond operations in my project.

ble_gap_sec_params_t m_sec_params;
ble_gap_sec_keyset_t m_sec_keyset;

ble_gap_enc_key_t m_own_enc_key; //need to be stored in flash
ble_gap_enc_key_t m_peer_enc_key;

static void sec_params_init()
{
memset(&m_sec_params, 0, sizeof(ble_gap_sec_params_t));

//Initialize m_sec_params
m_sec_params.bond = 1;
m_sec_params.mitm = 1;
m_sec_params.io_caps = BLE_GAP_IO_CAPS_DISPLAY_ONLY;
m_sec_params.min_key_size = 7;
m_sec_params.max_key_size = 16;

m_sec_params.kdist_own.enc = 1;
m_sec_params.kdist_own.id = 0;
m_sec_params.kdist_own.sign = 0;

m_sec_params.kdist_peer.enc = 1;
m_sec_params.kdist_peer.id = 0;
m_sec_params.kdist_peer.sign = 0;

memset(&m_sec_keyset, 0, sizeof(ble_gap_sec_keyset_t));
//Initialize m_sec_keyset
m_sec_keyset.keys_own.p_enc_key = &m_own_enc_key;
m_sec_keyset.keys_own.p_id_key = NULL;
m_sec_keyset.keys_own.p_pk = NULL;
m_sec_keyset.keys_own.p_sign_key = NULL;

m_sec_keyset.keys_peer.p_enc_key = &m_peer_enc_key;
m_sec_keyset.keys_peer.p_id_key = NULL;
m_sec_keyset.keys_peer.p_pk = NULL;
m_sec_keyset.keys_peer.p_sign_key = NULL;
}

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
uint32_t err_code;

switch (p_ble_evt->header.evt_id)
{
case BLE_GAP_EVT_CONNECTED:

err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
APP_ERROR_CHECK(err_code);
m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;

err_code = sd_ble_gap_authenticate(m_conn_handle,&m_sec_params);
APP_ERROR_CHECK(err_code);

break;

case BLE_GAP_EVT_DISCONNECTED:
err_code = bsp_indication_set(BSP_INDICATE_IDLE);
APP_ERROR_CHECK(err_code);
m_conn_handle = BLE_CONN_HANDLE_INVALID;
break;

case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
// Pairing not supported
// err_code = sd_ble_gap_sec_params_reply(m_conn_handle, BLE_GAP_SEC_STATUS_PAIRING_NOT_SUPP, NULL, NULL);
// APP_ERROR_CHECK(err_code);
sec_params_init();
err_code = sd_ble_gap_sec_params_reply( m_conn_handle,
BLE_GAP_SEC_STATUS_SUCCESS,
&m_sec_params,
&m_sec_keyset);
APP_ERROR_CHECK(err_code);

break;

case BLE_GATTS_EVT_SYS_ATTR_MISSING:
// No system attributes have been stored.
err_code = sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0, 0);
APP_ERROR_CHECK(err_code);
break;

case BLE_GAP_EVT_AUTH_STATUS:
if(p_ble_evt->evt.gap_evt.params.auth_status.auth_status == BLE_GAP_SEC_STATUS_SUCCESS)
{
printf("\r\npair success!!!\r\n");
}
else{
printf("\r\npair failed!!!\r\n");
sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
}

case BLE_GAP_EVT_PASSKEY_DISPLAY:
printf("\r\npasskey: %s\r\n",p_ble_evt->evt.gap_evt.params.passkey_display.passkey);

case BLE_GAP_EVT_SEC_INFO_REQUEST:
sd_ble_gap_sec_info_reply(m_conn_handle, &(m_own_enc_key.enc_info), NULL, NULL);
printf("BLE_GAP_EVT_SEC_INFO_REQUEST\n");
break;

default:
// No implementation needed.
break;
}
}

static void gap_params_init(void)
{
uint32_t err_code;
ble_gap_conn_params_t gap_conn_params;
ble_gap_conn_sec_mode_t sec_mode;

BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);

err_code = sd_ble_gap_device_name_set(&sec_mode,
(const uint8_t *) DEVICE_NAME,
strlen(DEVICE_NAME));
APP_ERROR_CHECK(err_code);

memset(&gap_conn_params, 0, sizeof(gap_conn_params));

gap_conn_params.min_conn_interval = MIN_CONN_INTERVAL;
gap_conn_params.max_conn_interval = MAX_CONN_INTERVAL;
gap_conn_params.slave_latency = SLAVE_LATENCY;
gap_conn_params.conn_sup_timeout = CONN_SUP_TIMEOUT;

err_code = sd_ble_gap_ppcp_set(&gap_conn_params);
APP_ERROR_CHECK(err_code);

uint8_t passkey[] = "123456";
m_static_pin_option.gap_opt.passkey.p_passkey = passkey;

err_code=sd_ble_opt_set(BLE_GAP_OPT_PASSKEY,&m_static_pin_option);
APP_ERROR_CHECK(err_code);
}

int main(void)
{
uint32_t err_code;
bool erase_bonds;

// Initialize.
APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);

uart_init();

buttons_leds_init(&erase_bonds); //button 1(@pcb key2,pin14) is used as delete bonding information
ble_stack_init();

gap_params_init();

services_init();
advertising_init();
conn_params_init();

printf("\r\nUART Start!\r\n");
err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
APP_ERROR_CHECK(err_code);

// Enter main loop.
for (;;)
{
power_manage();
}
}

[Hung Bui]

Hi Tianfei, 

It's hard to tell what could be wrong here. But have you made sure you managed to bond on the first connection ?  If you test with nRFConnect do you see the status change to "Bonded" ?

Do you have a particular reason of handling the bonding process on your own without using the peer manager library ? You can find the library used in most of our example in the SDK\example\ble_peripheral\ folder. I would suggest you to try the ble_app_proximity example. 

[tianfei00]

Dear Hung Bui,

        When testing and debuging the code, I used the nRFConnect  software in my smart phone. Everytime after I entered the satic key in my smartphone, the nRFConnect  shows bonded. And after disconnect with nRF52832, when I connect nRF52832 again, it will not need any pairing operations. 

        But every time I reset nRF52832, when my smart phone connect nRF52832, the phone also need to carry out pairing and bonding operations.

       The "ble_app_proximity " example I have refered in last week and I found it do not use static key when pairing. So this example can not solve my puzzled problem. 

Thanks very much for your help.

Best regards,

Tianfei

[Hung Bui]

Hi Tianfei, 

If you want passkey you can try the ble_app_gls example. If you want static passkey you would need to modify that example. 

It seemed that you didn't store bond information to flash. That's why when you restart the board you would need to do bonding again. Storing and managing bond information are handled by the peer manager library. We strongly suggest you to use the library.

If you want to implement that on your own, you need to follow this message sequence chart.  You need to store and restore the ediv, LTK to flash. 

[tianfei00]

Dear Hung Bui,

         Actually I deeply realized there are some variables or parameters needed to be stored in flash when I modified my code, but I really do not konw which variables needed to be stored in flash and how to store them？I do not konw the detailed step to store them in order to achieve the goal of my project. 

       I think I need your company the related official guide documents and related examples which can teach me how to implement the function step by step.

Thanks very much for your help.

Best regards,

Tianfei

[Hung Bui]

Hi Tianfei, 

You would need to follow the message sequence chart that I provided you. 

I still don't understand why you dont use our library ? Have you tried examples we provided in the ble_peripheral example folder ?