STM32WB55: BLE Pairing Works, but Bonding Fails - Bond List is Empty

[LwtRuben]

I'm developing a BLE central application on a NUCLEO-WB55RG board using the P2P_Client example as a base. I'm facing an issue where I can successfully pair with a peripheral, but the bonding information is never saved to non-volatile memory. Keep in mind I'm new to this field so it is very possible one of my steps in the process is wrong. The board being paired is an NRF52832 development board and the logs, which I will share later in the post, clearly state pairing was completed and bonding worked.

ENVIRONMENT

• NUCLEO-WB55RG: CENTRAL
  • FUS Version: v2.0.0.3
  • STACK Version: v1.22.1.1
  • FUS Operator: v3.1.0
• NRF52832 Development board: PERIPHERAL

PROBLEM DESCRIPTION

My application flow is as follows:

1. Scan and discover the peripheral.
2. Connect to the peripheral successfully.
3. Initiate pairing using aci_gap_send_pairing_req().
4. Receive the ACI_GAP_PAIRING_COMPLETE_VSEVT_CODE event with a success status (0x00).
5. After I manually disconnect or reset the device, I check for bonded devices using aci_gap_get_bonded_devices().
6. The function always reports that the number of bonded devices is zero.

WHAT I'VE ALREADY TRIED

I've tried:

1. Disconnecting right after pairing and waiting 1 second to check bonded devices.
2. Power cycled and checked bonded devices on boot (still nothing).
3. Updated BLE stack.
4. Keeping the connection after pairing. After boot up, still no bonded devices.

CONFIGURATION & CODE

Here's my app_conf.h

#define CFG_BONDING_MODE                 (1)
#define CFG_FIXED_PIN                    (111111)
#define CFG_USED_FIXED_PIN               (0)
#define CFG_ENCRYPTION_KEY_SIZE_MAX      (16)
#define CFG_ENCRYPTION_KEY_SIZE_MIN      (8)
...
#define CFG_IO_CAPABILITY                     CFG_IO_CAPABILITY_NO_INPUT_NO_OUTPUT
...
#define CFG_MITM_PROTECTION                   CFG_MITM_PROTECTION_NOT_REQUIRED
...
#define CFG_SC_SUPPORT                        CFG_SECURE_OPTIONAL
...
#define CFG_KEYPRESS_NOTIFICATION_SUPPORT     CFG_KEYPRESS_NOT_SUPPORTED

And here's the relevant app_ble code blocks (I will also attach the file, forgive the mess I'm just trying to get a prototype working).

static void Ble_Hci_Gap_Gatt_Init(void)
{
...
BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.mitm_mode = CFG_MITM_PROTECTION;
  BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.encryptionKeySizeMin = CFG_ENCRYPTION_KEY_SIZE_MIN;
  BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.encryptionKeySizeMax = CFG_ENCRYPTION_KEY_SIZE_MAX;
  BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.Use_Fixed_Pin = CFG_USED_FIXED_PIN;
  BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.Fixed_Pin = CFG_FIXED_PIN;
  BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.bonding_mode = CFG_BONDING_MODE;

  ret = aci_gap_set_authentication_requirement(BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.bonding_mode,
                                               BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.mitm_mode,
                                               CFG_SC_SUPPORT,
                                               CFG_KEYPRESS_NOTIFICATION_SUPPORT,
                                               BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.encryptionKeySizeMin,
                                               BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.encryptionKeySizeMax,
                                               BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.Use_Fixed_Pin,
                                               BleApplicationContext.BleApplicationContext_legacy.bleSecurityParam.Fixed_Pin,
                                               CFG_IDENTITY_ADDRESS);
...
}

static void GetBondedDevices(void) {
	tBleStatus ret;
	    uint8_t num_bonded_devices = 0;

	    /* Assuming a maximum of CFG_BLE_NUM_LINK bonded devices can be stored.
	     * Adjust the size of `bonded_device_list` if necessary.
	     */
	    Bonded_Device_Entry_t bonded_device_list[CFG_BLE_NUM_LINK];

	    /* Get the list of bonded devices from the BLE stack's security database. */
	    ret = aci_gap_get_bonded_devices(&num_bonded_devices, bonded_device_list);

	    if (ret == BLE_STATUS_SUCCESS) {
	        APP_DBG_MSG("\r\n\r** BONDED DEVICE LIST (Total: %d) **\n\r", num_bonded_devices);

	        if (num_bonded_devices > 0) {
	            for (int i = 0; i < num_bonded_devices; i++) {
	                APP_DBG_MSG("  -> Device %d: \n\r", i + 1);
	                APP_DBG_MSG("     - BD_ADDR: %02X:%02X:%02X:%02X:%02X:%02X\n\r",
	                            bonded_device_list[i].Address[5],
	                            bonded_device_list[i].Address[4],
	                            bonded_device_list[i].Address[3],
	                            bonded_device_list[i].Address[2],
	                            bonded_device_list[i].Address[1],
	                            bonded_device_list[i].Address[0]);
	            }
	        } else {
	            APP_DBG_MSG("  -> No bonded devices found.\n\r");
	        }
	    } else {
	        APP_DBG_MSG("  -> Failed to get bonded devices, result: 0x%x \n\r", ret);
	    }
}

static void PairTask(void) {
    APP_DBG_MSG("PAIRING REQUEST");

    tBleStatus ret = aci_gap_send_pairing_req(BleApplicationContext.BleApplicationContext_legacy.connectionHandle, 0); /* Force_Rebond set to 0 (No) */
      APP_DBG_MSG("aci_gap_send_pairing_req command, result: 0x%x\n", ret);
}

I'm using tasks so these PairTask and GetBondedDevices are called using the sequencer.

LOGS FROM STM32 SIDE

[app_ble.c][SVCCTL_App_Notification][570]

** CONNECTION COMPLETE EVENT WITH SERVER

[app_ble.c][SVCCTL_App_Notification][575] -> Sending Pairing Request 8010x

[app_ble.c][PairTask][1115] PAIRING REQUEST

[app_ble.c][PairTask][1118] aci_gap_send_pairing_req command, result: 0x0

[app_ble.c][SVCCTL_App_Notification][540] DISCONNECTION EVENT: Reason = 0x3E

[app_ble.c][SVCCTL_App_Notification][541]

** DISCONNECTION EVENT WITH SERVER 00x

[app_ble.c][GetBondedDevices][1139]

** BONDED DEVICE LIST (Total: 0) **

[app_ble.c][GetBondedDevices][1153] -> No bonded devices found.

LOGS FROM NRF SIDE

*** Booting nRF Connect SDK v2.9.2-4ab7b98fc76f ***

*** Using Zephyr OS v3.7.99-aa34a5632971 ***

Starting Bluetooth Peripheral BMS example

I: 2 Sectors of 4096 bytes

I: alloc wra: 0, f28

I: data wra: 0, 1d8

I: SoftDevice Controller build revision:

I: 8c 08 59 97 97 6b e1 de |..Y..k..

I: 80 e5 fd f6 b4 58 ff 37 |.....X.7

I: d9 6d e5 58 |.m.X

I: HW Platform: Nordic Semiconductor (0x0002)

I: HW Variant: nRF52x (0x0002)

I: Firmware: Standard Bluetooth controller (0x00) Version 140.22792 Build 3781924759

I: No ID address. App must call settings_load()

Bluetooth initialized

I: Identity: CC:EE:C2:73:D3:31 (random)

I: HCI: version 6.0 (0x0e) revision 0x10fd, manufacturer 0x0059

I: LMP: version 6.0 (0x0e) subver 0x10fd

Advertising successfully started

Connected

Confirming pairing for 00:80:E1:27:57:A7 (public)

Security changed: 00:80:E1:27:57:A7 (public) level 2

Pairing completed: 00:80:E1:27:57:A7 (public), bonded: 1

Disconnected, reason 0x08

MY QUESTION

Am I missing something? Could it be related to the NRF52832 device potentially not being the proper address type for the type of bonding that I'm doing?