About the number of saved bonding information

[sdi_kei]

Hello.
I am developing using nrf52832 (S132 v7.0.1, SDK v16.0.0).

I use whitelist to store bonding information. Is there an upper limit to the number that can be stored?
Also, how can I set it to increase the number that can be saved?

If you have any materials, please let me know.
Please let us know if you have any questions.
Thank you.

[Hung Bui]

Hi Kei, 

The number of peers can be handled by the peer manager is defined by the flash space that's the fds module has. 
It's defined in sdk_config.h as FDS_VIRTUAL_PAGES (by default 3 pages) . So there isn't really a limit for number of peer in peer manager. You can just increase the number of page reserved for FDS.

However, there is a limit for whitelisting. It's the limitation of the hardware. So the softdevice only allow a whitelist of max 8 devices (BLE_GAP_WHITELIST_ADDR_MAX_COUNT). 
A workaround for this is to rotate this 8 devices list. So for example if you have 16 devices you want to put into the whitelist, you can scan/advertise with 8 devices in whitelist at a time, and then switch. 

[sdi_kei]

thank you for your answer.

When connecting to a BLE device and performing bonding, the information may be listed in the FDS using a white list.
Therefore, I thought that all of them were registered on the white list.

The action I want to do is receive advertisements from bonded BLE devices. For that purpose, I thought that by setting "filter_policy" to "BLE_GAP_SCAN_FP_WHITELIST", it would be possible to receive advertisements only for bonded BLE devices.

How should I register for the white list?
And how do you rotate the devices you want to whitelist?

Thank you.

[Hung Bui]

Hi Kei, 

You can have a look at the ble_app_hids_mouse as an example on how you can setup the whitelist for scanning/advertising. The function to setup the whitelist is whitelist_set(): 

/**@brief Function for setting filtered whitelist.
 *
 * @param[in] skip  Filter passed to @ref pm_peer_id_list.
 */
static void whitelist_set(pm_peer_id_list_skip_t skip)
{
    pm_peer_id_t peer_ids[BLE_GAP_WHITELIST_ADDR_MAX_COUNT];
    uint32_t     peer_id_count = BLE_GAP_WHITELIST_ADDR_MAX_COUNT;

    ret_code_t err_code = pm_peer_id_list(peer_ids, &peer_id_count, PM_PEER_ID_INVALID, skip);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_INFO("\tm_whitelist_peer_cnt %d, MAX_PEERS_WLIST %d",
                   peer_id_count + 1,
                   BLE_GAP_WHITELIST_ADDR_MAX_COUNT);

    err_code = pm_whitelist_set(peer_ids, peer_id_count);
    APP_ERROR_CHECK(err_code);
}

However this code will load all peers and it will be limited by BLE_GAP_WHITELIST_ADDR_MAX_COUNT = 8. 

If you want to rotate the list, you would need to study the code a little bit and call pm_whitelist_set() so that it will switch between peer_ids. I haven't tried, but it may work this way: 
First call: 
err_code = pm_whitelist_set(peer_ids, 8);
APP_ERROR_CHECK(err_code);

Second call (after you scan for  a while) 

err_code = pm_whitelist_set(peer_ids+sizeof(uint16_t)*8, 8);
APP_ERROR_CHECK(err_code);

And so on. I suggest to look deeper into the code of the peer manager to understand how the whitelist setting works. 

[sdi_kei]

Hello.

I'm considering rotating the list.
I am trying to do pm_whitelist_set 1 second after setting with pm_whitelist_set. (Switch peer_ids)
However, when I make the second call, I get a BLE_GAP_ERROR_WHITELIST_IN_USE error.
I tried to clear the whitelist before setting, but I got the same error.

Is there any countermeasure?

Thank you.

[Hung Bui]

Hi Kei, 

Could you try to stop scanning (and advertising if you also do advertising) before you change the whitelist ? It's mentioned in the documentation of sd_ble_gap_whitelist_set() that "The whitelist cannot be set if a BLE role is using the whitelist."

[sdi_kei]

Hello.

Changed to do sd_ble_gap_scan_stop before doing pm_whitelist_set. Thanks to you, BLE_GAP_ERROR_WHITELIST_IN_USE no longer occurs.
However, the second call now causes an NRF_ERROR_NOT_FOUND.

I described the process of rotating with reference to whitelist_load of ble_app_gatts. The source code is as follows.

Which part should I fix?

Thank you.

#define BLE_GAP_WHITELIST_ADDR_MAX_COUNT (1)
static uint8_t whitelist_cnt;

void whitelist_load(void)
{
    ret_code_t   ret;
    pm_peer_id_t peers[BLE_GAP_WHITELIST_ADDR_MAX_COUNT];
    uint32_t     peer_cnt;
    
    memset(peers, PM_PEER_ID_INVALID, sizeof(peers));
    peer_cnt = (sizeof(peers) / sizeof(pm_peer_id_t));

    // Load all peers from flash and whitelist them.
    peer_list_get(peers, &peer_cnt);
    
    if (whitelist_cnt >= pm_peer_count())
    {
        whitelist_cnt = 0;
    }

    ret = pm_whitelist_set(peers + (sizeof(uint16_t) * (BLE_GAP_WHITELIST_ADDR_MAX_COUNT * whitelist_cnt)), peer_cnt);
    APP_ERROR_CHECK(ret);

    // Setup the device identities list.
    // Some SoftDevices do not support this feature.
    ret = pm_device_identities_list_set(peers, peer_cnt);
    if (ret != NRF_ERROR_NOT_SUPPORTED)
    {
        APP_ERROR_CHECK(ret);
    }
}