Secure DFU from s130/s132

[Gili Elias]

Hi, We're using a 51422 with s130 to perform OTA DFU.

Both bases for bootloader and central are from sdk 12.2.

We have already implemented the older DFU (non-secure) for nRF51, which was a 128bit UUID, and it is working fine.

We started implementing the nRF52 DFU (16bit - 0xFE59). The initial conenction is successful, but when reaching the on_db_disc_evt, we get 2 characteristics that have 0 in both UUID and type.

Is this correct? If so, how do you distinguish between the characteristics and assign them?

This is the code for registering the service:

uint32_t ble_sdfu_c_init(ble_sdfu_c_t * p_ble_sdfu_c, ble_sdfu_c_init_t * p_ble_sdfu_c_init)
{
    VERIFY_PARAM_NOT_NULL(p_ble_sdfu_c);
    VERIFY_PARAM_NOT_NULL(p_ble_sdfu_c_init);
    
    ble_uuid_t    sdfu_uuid = {
        .type = BLE_UUID_TYPE_BLE,
        .uuid = BLE_UUID_SDFU_SERVICE,  // 0xFE59
    };

    p_ble_sdfu_c->evt_handler                         = p_ble_sdfu_c_init->evt_handler;
    p_ble_sdfu_c->conn_handle                         = BLE_CONN_HANDLE_INVALID;
    p_ble_sdfu_c->handles.sdfu_control_point_handle   = BLE_GATT_HANDLE_INVALID;
    p_ble_sdfu_c->handles.sdfu_packet_handle          = BLE_GATT_HANDLE_INVALID;

    return ble_db_discovery_evt_register(&sdfu_uuid);
}

And this is the callback for the service discovery:

void ble_sdfu_c_on_db_disc_evt(ble_sdfu_c_t * p_ble_sdfu_c, ble_db_discovery_evt_t * p_evt)
{
    ble_sdfu_c_evt_t sdfu_c_evt;
    memset(&sdfu_c_evt,0,sizeof(ble_sdfu_c_evt_t));

    ble_gatt_db_char_t * p_chars = p_evt->params.discovered_db.charateristics;

    // Check if the DFU was discovered.
    if (p_evt->evt_type == BLE_DB_DISCOVERY_COMPLETE &&
        p_evt->params.discovered_db.srv_uuid.uuid == BLE_UUID_SDFU_SERVICE &&
        p_evt->params.discovered_db.srv_uuid.type == BLE_UUID_TYPE_BLE) //p_ble_sdfu_c->uuid_type)
    {
        for (uint32_t i = 0; i < p_evt->params.discovered_db.char_count; i++)
        {
            switch (p_chars[i].characteristic.uuid.uuid)   // <= THIS IS ALWAYS 0
            {
                case BLE_UUID_SDFU_CONTROL_POINT_CHARACTERISTIC:
                    sdfu_c_evt.handles.sdfu_control_point_handle = p_chars[i].characteristic.handle_value;
                    sdfu_c_evt.handles.sdfu_control_point_cccd_handle = p_chars[i].cccd_handle;
                    break;

                case BLE_UUID_SDFU_PACKET_CHARACTERISTIC:
                    sdfu_c_evt.handles.sdfu_packet_handle = p_chars[i].characteristic.handle_value;
                    break;

                default:
                    break;
            }
        }
        if (p_ble_sdfu_c->evt_handler != NULL)
        {
            sdfu_c_evt.conn_handle = p_evt->conn_handle;
            sdfu_c_evt.evt_type    = SDFU_C_EVT_DISCOVERY_COMPLETE;
            p_ble_sdfu_c->evt_handler(p_ble_sdfu_c, &sdfu_c_evt);
        }
    }
}

[Gili Elias]

Unfortunately, I can't share the project at the moment. Is there any other specific part of code you'd like to see?

How do I read the 128bit of the discovered characteristics? The ble_gattc_char_t struct that is passed to the event handler has only 16bit (or octets 12-13 of 128-bit UUID), but as I said, both handles has 0 in this parameter.

For now, the only way I've managed to bypass this issue is to hard code char[0] as the packet handle and char[1] as the control point (I based this on the properties values). Obviously this is not ideal.