How to get pairing/bonding to work in e.g. ble_app_uart

   Hello List,

First some context: I am working with SDK 17.1.0 on a nrf52840 (arduino nano ble).

Created a variant of the ble_app_uart example and want to add pairing/bonding with it. Started looking at ble_app_hrs to start.

Basically I added functions "peer_manager_init" and "pm_evt_handler" and some changes to "sdk_config.h", but now am stuck. Please see below for that code.

With this code it just works, but without pairing/bonding.

If I remove the "pm_conn_sec_params_reply" call from "pm_evt_handler" the smartphone pops up a window and asks whether there should be a pairing, which then fails as can be seen using the RTT-log:

<error> peer_manager_sm: Could not perform security procedure. smd_params_reply() or smd_link_secure() returned NRF_ERROR_INVALID_ADDR. conn_handle: 0
<error> peer_manager_handler: Unexpected fatal error occurred: error: NRF_ERROR_INVALID_ADDR
<error> peer_manager_handler: Asserting.
<error> app: Fatal error

One thing that is missing is setting the pin code in the program, how is that to be done?

Hopefully someone can help me in the right direction.

Thanks in advance, Sietse

Here the code snipped.

// peer_manager stuff in main.c
      
#include "peer_manager.h"
#include "peer_manager_handler.h"
#include "fds.h"

#define SEC_PARAM_BOND                      1                                       /**< Perform bonding. */
#define SEC_PARAM_MITM                      0                                       /**< Man In The Middle protection not required. */
#define SEC_PARAM_LESC                      1                                       /**< LE Secure Connections enabled. */
#define SEC_PARAM_KEYPRESS                  0                                       /**< Keypress notifications not enabled. */
#define SEC_PARAM_IO_CAPABILITIES           BLE_GAP_IO_CAPS_NONE                    /**< No I/O capabilities. */
#define SEC_PARAM_OOB                       0                                       /**< Out Of Band data not available. */
#define SEC_PARAM_MIN_KEY_SIZE              7                                       /**< Minimum encryption key size. */
#define SEC_PARAM_MAX_KEY_SIZE              16                                      /**< Maximum encryption key size. */


static void pm_evt_handler(pm_evt_t const * p_evt)
{
    pm_handler_on_pm_evt(p_evt);
    pm_handler_disconnect_on_sec_failure(p_evt);
    pm_handler_flash_clean(p_evt);

    switch (p_evt->evt_id)
      {
      case PM_EVT_PEERS_DELETE_SUCCEEDED:
	advertising_start();
	break;

      case  PM_EVT_CONN_SEC_SUCCEEDED:
	NRF_LOG_INFO("--> PM_EVT_CONN_SEC_SUCCEEDED");
	break;
      case  PM_EVT_CONN_SEC_PARAMS_REQ:
	NRF_LOG_INFO("--> PM_EVT_CONN_SEC_PARAMS_REQ");
	pm_conn_sec_params_reply(p_evt->conn_handle,
				 p_evt->params.conn_sec_params_req.p_peer_params,
				 p_evt->params.conn_sec_params_req.p_context);
	break;
      default:
	NRF_LOG_INFO("--> pm_evt_handler %d", p_evt->evt_id);
	break;
    }
}



/**@brief Function for the Peer Manager initialization.
 */

static void peer_manager_init(void)
{
    ble_gap_sec_params_t sec_param;
    ret_code_t           err_code;

    err_code = pm_init();
    APP_ERROR_CHECK(err_code);

    memset(&sec_param, 0, sizeof(ble_gap_sec_params_t));

    // Security parameters to be used for all security procedures.
    sec_param.bond           = SEC_PARAM_BOND;
    sec_param.mitm           = SEC_PARAM_MITM;
    sec_param.lesc           = SEC_PARAM_LESC;
    sec_param.keypress       = SEC_PARAM_KEYPRESS;
    sec_param.io_caps        = SEC_PARAM_IO_CAPABILITIES;
    sec_param.oob            = SEC_PARAM_OOB;
    sec_param.min_key_size   = SEC_PARAM_MIN_KEY_SIZE;
    sec_param.max_key_size   = SEC_PARAM_MAX_KEY_SIZE;
    sec_param.kdist_own.enc  = 1;
    sec_param.kdist_own.id   = 1;
    sec_param.kdist_peer.enc = 1;
    sec_param.kdist_peer.id  = 1;

    err_code = pm_sec_params_set(&sec_param);
    APP_ERROR_CHECK(err_code);

    err_code = pm_register(pm_evt_handler);
    APP_ERROR_CHECK(err_code);
}


  • forgot to mention that I had to remove -Werror from the CFLAGS in the Makefile. Otherwise I get the following error:

    ... commands.c:1005:39: warning: passing argument 2 of 'pm_conn_sec_params_reply' discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
    1005 | p_evt->params.conn_sec_params_req.p_peer_params,

    In file included from ../../../main.c:61:
    /home/sietse/Radio/Software/Nordic/nRF5_SDK_17.1.0_ddde560/components/ble/peer_manager/peer_manager.h:220:60: note: expected 'ble_gap_sec_params_t *' but argument is of type 'const ble_gap_sec_params_t * const'
    220 | ble_gap_sec_params_t * p_sec_params,

  • Hi

    This error seems very strange, as the  smd_params_reply() or smd_link_secure() don't have NRF_ERROR_INVALID_ADDR as a return value, so the error message doesn't make much sense to me. Have you checked out the Peer Manager documentation and the Usage chapter that shows how to typically add the Peer Manager and thus pairing/bonding to an application?

    The project you're making is for a peripheral device, is that correct? What device are you trying to pair/bond to exactly? Another nRF device or a phone/computer?

    Best regards,

    Simon


  • Thanks for the reply!


    I am indeed trying do make a periphiral (ble_periphiral/ble_app_uart) and connect to android or PC (Linux).
    I now created a version that ONLY added the (hopefully) relevant parts from ble_app_hrs to ble_app_uart_pair.
    For completeness here the code.

    ble_app_uart_pair.zip

    See the diff between main.c and main.c_org for the additions.
    There also are some differences in sdk_config.h and the Makefile of course.
    The Makefile_pca10056 is a version for use with BOARD_PCA10056.
    Now to my problem.

    I re-read the documentation about the peer manager and found one error I think.
    I mistakenly had "PM_CENTRAL_ENABLE 1" in sdk_config.h. Changed this to 0, but nothing changed.

    So, the app works fine (with android and PC), but there is no pairing at all!
    Here RTT log from a short session:
    <info> app: --> PM_EVT_CONN_SEC_PARAMS_REQ
    <debug> app: --> pm_conn_secure return: 0
    <debug> nrf_ble_gatt: ATT MTU updated to 247 bytes on connection 0x0 (response).
    <info> app: Data len is set to 0xF4(244)
    <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
    <debug> nrf_ble_gatt: Data length updated to 251 on connection 0x0.
    <debug> nrf_ble_gatt: max_rx_octets: 251
    <debug> nrf_ble_gatt: max_tx_octets: 251
    <debug> nrf_ble_gatt: max_rx_time: 2120
    <debug> nrf_ble_gatt: max_tx_time: 2120
    <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
    <debug> nrf_ble_gatt: Peer on connection 0x0 requested an ATT MTU of 517 bytes.
    <debug> nrf_ble_gatt: Updating ATT MTU to 247 bytes (desired: 247) on connection 0x0.
    <info> app: Data len is set to 0xF4(244)
    <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
    <debug> app: Received data from BLE NUS. Writing data on UART.
    <debug> app: 66 20 67 20 66 |f g f
    <info> app: Disconnected

    Note that pm_conn_service is called but there is no PM_EVT_CONN_SEC_START event!

    But, if the pairing is initiated on linux, by doing a "bluetoothctl pair E7:05:43:10:93:D3" I get the following reaction:
    On linux:
    Attempting to pair with E7:05:43:10:93:D3
    [CHG] Device E7:05:43:10:93:D3 Connected: yes
    [CHG] Device E7:05:43:10:93:D3 Connected: no
    Failed to pair: org.bluez.Error.AuthenticationCanceled

    and via RTT from the target:
    <info> app: --> PM_EVT_CONN_SEC_PARAMS_REQ
    <debug> app: --> pm_conn_secure return: 0
    <debug> nrf_ble_gatt: Data length updated to 251 on connection 0x0.
    <debug> nrf_ble_gatt: max_rx_octets: 251
    <debug> nrf_ble_gatt: max_tx_octets: 251
    <debug> nrf_ble_gatt: max_rx_time: 2120
    <debug> nrf_ble_gatt: max_tx_time: 2120
    <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
    <info> app: --> pm_evt_handler 2
    <info> app: --> PM_EVT_CONN_SEC_PARAMS_REQ
    <error> app: Fatal error

    Note that "pm_evt_handler 2" is PM_EVT_CONN_SEC_START
    So now we get a little bit further.
    But, why the fatal error?

    Thanks again, Sietse

    PS. And if it had worked, where could I have set the required pincode on the target?

  • Hi again

    Is there a reason you are using ble_app_hrs as a template for adding pairing/bonding? That example project does neither, and I would recommend looking at ble_app_bms or ble_app_gls instead which actually do pairing/bonding.

    The "pm_evt_handler" with event ID 2 could be that it disconnects on a security failure perhaps.

    Best regards,

    Simon

  • Hello again,

    I was using ble_app_hrs because somewhere I was pointed to it for pairing/bonding.
    I now tried _bms en _gls that both work.
    Then I tried to get the pair/bond stuff into my ble_app_uart_pair, here the new main.c,
    the only file that changed.

    /**
     * Copyright (c) 2014 - 2021, Nordic Semiconductor ASA
     *
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without modification,
     * are permitted provided that the following conditions are met:
     *
     * 1. Redistributions of source code must retain the above copyright notice, this
     *    list of conditions and the following disclaimer.
     *
     * 2. Redistributions in binary form, except as embedded into a Nordic
     *    Semiconductor ASA integrated circuit in a product or a software update for
     *    such product, must reproduce the above copyright notice, this list of
     *    conditions and the following disclaimer in the documentation and/or other
     *    materials provided with the distribution.
     *
     * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
     *    contributors may be used to endorse or promote products derived from this
     *    software without specific prior written permission.
     *
     * 4. This software, with or without modification, must only be used with a
     *    Nordic Semiconductor ASA integrated circuit.
     *
     * 5. Any software provided in binary form under this license must not be reverse
     *    engineered, decompiled, modified and/or disassembled.
     *
     * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
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     * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
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     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    /** @file
     *
     * @defgroup ble_sdk_uart_over_ble_main main.c
     * @{
     * @ingroup  ble_sdk_app_nus_eval
     * @brief    UART over BLE application main file.
     *
     * This file contains the source code for a sample application that uses the Nordic UART service.
     * This application uses the @ref srvlib_conn_params module.
    
     With pairing/bonding from ble_app_gls.
    
     */
    
    
    #include <stdint.h>
    #include <string.h>
    #include "nordic_common.h"
    #include "nrf.h"
    #include "ble_hci.h"
    #include "ble_advdata.h"
    #include "ble_advertising.h"
    #include "ble_conn_params.h"
    #include "nrf_sdh.h"
    #include "nrf_sdh_soc.h"
    #include "nrf_sdh_ble.h"
    #include "nrf_ble_gatt.h"
    #include "nrf_ble_qwr.h"
    #include "app_timer.h"
    #include "ble_nus.h"
    #include "app_uart.h"
    #include "app_util_platform.h"
    #include "bsp_btn_ble.h"
    #include "nrf_pwr_mgmt.h"
    
    #if defined (UART_PRESENT)
    #include "nrf_uart.h"
    #endif
    #if defined (UARTE_PRESENT)
    #include "nrf_uarte.h"
    #endif
    
    #include "nrf_log.h"
    #include "nrf_log_ctrl.h"
    #include "nrf_log_default_backends.h"
    
    // added for peer manager
    #include "nrf_ble_lesc.h"
    #include "fds.h"
    #include "peer_manager.h"
    #include "peer_manager_handler.h"
    
    #define DEVICE_NAME                     "Nordic_UART"                               /**< Name of device. Will be included in the advertising data. */
    #define NUS_SERVICE_UUID_TYPE           BLE_UUID_TYPE_VENDOR_BEGIN                  /**< UUID type for the Nordic UART Service (vendor specific). */
    
    #define APP_BLE_OBSERVER_PRIO           3                                           /**< Application's BLE observer priority. You shouldn't need to modify this value. */
    #define APP_BLE_CONN_CFG_TAG            1                                           /**< A tag identifying the SoftDevice BLE configuration. */
    
    #define APP_ADV_INTERVAL                64                                          /**< The advertising interval (in units of 0.625 ms. This value corresponds to 40 ms). */
    
    #define APP_ADV_DURATION                18000                                       /**< The advertising duration (180 seconds) in units of 10 milliseconds. */
    
    #define MIN_CONN_INTERVAL               MSEC_TO_UNITS(20, UNIT_1_25_MS)             /**< Minimum acceptable connection interval (20 ms), Connection interval uses 1.25 ms units. */
    #define MAX_CONN_INTERVAL               MSEC_TO_UNITS(75, UNIT_1_25_MS)             /**< Maximum acceptable connection interval (75 ms), Connection interval uses 1.25 ms units. */
    #define SLAVE_LATENCY                   0                                           /**< Slave latency. */
    #define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(4000, UNIT_10_MS)             /**< Connection supervisory timeout (4 seconds), Supervision Timeout uses 10 ms units. */
    #define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(5000)                       /**< Time from initiating event (connect or start of notification) to first time sd_ble_gap_conn_param_update is called (5 seconds). */
    #define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(30000)                      /**< Time between each call to sd_ble_gap_conn_param_update after the first call (30 seconds). */
    #define MAX_CONN_PARAMS_UPDATE_COUNT    3                                           /**< Number of attempts before giving up the connection parameter negotiation. */
    
    #define SEC_PARAM_BOND                      1                                       /**< Perform bonding. */
    #define SEC_PARAM_MITM                      1                                       /**< Man In The Middle protection required (applicable when display module is detected). */
    #define SEC_PARAM_LESC                      1                                       /**< LE Secure Connections enabled. */
    #define SEC_PARAM_KEYPRESS                  0                                       /**< Keypress notifications not enabled. */
    #define SEC_PARAM_IO_CAPABILITIES           BLE_GAP_IO_CAPS_DISPLAY_ONLY            /**< Display I/O capabilities. */
    #define SEC_PARAM_OOB                       0                                       /**< Out Of Band data not available. */
    #define SEC_PARAM_MIN_KEY_SIZE              7                                       /**< Minimum encryption key size. */
    #define SEC_PARAM_MAX_KEY_SIZE              16                                      /**< Maximum encryption key size. */
    
    #define PASSKEY_TXT                     "Passkey:"                                  /**< Message to be displayed together with the pass-key. */
    #define PASSKEY_TXT_LENGTH              8                                           /**< Length of message to be displayed together with the pass-key. */
    #define PASSKEY_LENGTH                  6                                           /**< Length of pass-key received by the stack for display. */
    
    #define DEAD_BEEF                       0xDEADBEEF                                  /**< Value used as error code on stack dump, can be used to identify stack location on stack unwind. */
    
    #define UART_TX_BUF_SIZE                256                                         /**< UART TX buffer size. */
    #define UART_RX_BUF_SIZE                256                                         /**< UART RX buffer size. */
    
    
    BLE_NUS_DEF(m_nus, NRF_SDH_BLE_TOTAL_LINK_COUNT);                                   /**< BLE NUS service instance. */
    NRF_BLE_GATT_DEF(m_gatt);                                                           /**< GATT module instance. */
    NRF_BLE_QWR_DEF(m_qwr);                                                             /**< Context for the Queued Write module.*/
    BLE_ADVERTISING_DEF(m_advertising);                                                 /**< Advertising module instance. */
    
    static pm_peer_id_t m_peer_to_be_deleted = PM_PEER_ID_INVALID;
    static uint16_t   m_conn_handle          = BLE_CONN_HANDLE_INVALID;                 /**< Handle of the current connection. */
    static uint16_t   m_ble_nus_max_data_len = BLE_GATT_ATT_MTU_DEFAULT - 3;            /**< Maximum length of data (in bytes) that can be transmitted to the peer by the Nordic UART service module. */
    static ble_uuid_t m_adv_uuids[]          =                                          /**< Universally unique service identifier. */
    {
        {BLE_UUID_NUS_SERVICE, NUS_SERVICE_UUID_TYPE}
    };
    
    
    static void advertising_start(bool erase_bonds);
    
    /**@brief Function for assert macro callback.
     *
     * @details This function will be called in case of an assert in the SoftDevice.
     *
     * @warning This handler is an example only and does not fit a final product. You need to analyse
     *          how your product is supposed to react in case of Assert.
     * @warning On assert from the SoftDevice, the system can only recover on reset.
     *
     * @param[in] line_num    Line number of the failing ASSERT call.
     * @param[in] p_file_name File name of the failing ASSERT call.
     */
    void assert_nrf_callback(uint16_t line_num, const uint8_t * p_file_name)
    {
        app_error_handler(DEAD_BEEF, line_num, p_file_name);
    }
    
    /**@brief Function for handling Peer Manager events.
     *
     * @param[in] p_evt  Peer Manager event.
     */
    
    static void pm_evt_handler(pm_evt_t const * p_evt)
    {
        ret_code_t err_code;
    
        pm_handler_on_pm_evt(p_evt);
        pm_handler_disconnect_on_sec_failure(p_evt);
        pm_handler_flash_clean(p_evt);
    
        switch (p_evt->evt_id)
          {
          case  PM_EVT_CONN_SEC_SUCCEEDED:
    	NRF_LOG_INFO("--> PM_EVT_CONN_SEC_SUCCEEDED");
    	pm_conn_sec_status_t conn_sec_status;
    
    	// Check if the link is authenticated (meaning at least MITM).
    	err_code = pm_conn_sec_status_get(p_evt->conn_handle, &conn_sec_status);
    	APP_ERROR_CHECK(err_code);
    
    	if (conn_sec_status.mitm_protected)
    	  {
    	    NRF_LOG_INFO("Link secured. Role: %d. conn_handle: %d, Procedure: %d",
    			 ble_conn_state_role(p_evt->conn_handle),
    			 p_evt->conn_handle,
    			 p_evt->params.conn_sec_succeeded.procedure);
    	  }
    	else
    	  {
    	    // The peer did not use MITM, disconnect.
    	    NRF_LOG_INFO("Collector did not use MITM, disconnecting");
    	    err_code = pm_peer_id_get(m_conn_handle, &m_peer_to_be_deleted);
    	    APP_ERROR_CHECK(err_code);
    	    err_code = sd_ble_gap_disconnect(m_conn_handle,
    					     BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
    	    APP_ERROR_CHECK(err_code);
    	  }
    
    	break;
          case PM_EVT_CONN_SEC_FAILED:
    	m_conn_handle = BLE_CONN_HANDLE_INVALID;
    	break;
    
          case  PM_EVT_CONN_SEC_PARAMS_REQ:
    	NRF_LOG_INFO("--> PM_EVT_CONN_SEC_PARAMS_REQ");
    	pm_conn_sec_params_reply(p_evt->conn_handle,
    				 p_evt->params.conn_sec_params_req.p_peer_params,
    				 p_evt->params.conn_sec_params_req.p_context);
    	break;
    
          case PM_EVT_PEERS_DELETE_SUCCEEDED:
    	advertising_start(false);
    	break;
    
          default:
    	NRF_LOG_INFO("--> pm_evt_handler %d", p_evt->evt_id);
    	break;
        }
    }
    
    /**@brief Function for initializing the timer module.
     */
    static void timers_init(void)
    {
        ret_code_t err_code = app_timer_init();
        APP_ERROR_CHECK(err_code);
    }
    
    /**@brief Function for the GAP initialization.
     *
     * @details This function will set up all the necessary GAP (Generic Access Profile) parameters of
     *          the device. It also sets the permissions and appearance.
     */
    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);
    
        err_code = sd_ble_gap_appearance_set(BLE_APPEARANCE_GENERIC_DISPLAY);
        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);
    }
    
    /**@brief Function for handling events from the GATT library. */
    void gatt_evt_handler(nrf_ble_gatt_t * p_gatt, nrf_ble_gatt_evt_t const * p_evt)
    {
        if ((m_conn_handle == p_evt->conn_handle) && (p_evt->evt_id == NRF_BLE_GATT_EVT_ATT_MTU_UPDATED))
        {
            m_ble_nus_max_data_len = p_evt->params.att_mtu_effective - OPCODE_LENGTH - HANDLE_LENGTH;
            NRF_LOG_INFO("Data len is set to 0x%X(%d)", m_ble_nus_max_data_len, m_ble_nus_max_data_len);
        }
        NRF_LOG_DEBUG("ATT MTU exchange completed. central 0x%x peripheral 0x%x",
                      p_gatt->att_mtu_desired_central,
                      p_gatt->att_mtu_desired_periph);
    }
    
    
    /**@brief Function for initializing the GATT library. */
    void gatt_init(void)
    {
        ret_code_t err_code;
    
        err_code = nrf_ble_gatt_init(&m_gatt, gatt_evt_handler);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_ble_gatt_att_mtu_periph_set(&m_gatt, NRF_SDH_BLE_GATT_MAX_MTU_SIZE);
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for handling Queued Write Module errors.
     *
     * @details A pointer to this function will be passed to each service which may need to inform the
     *          application about an error.
     *
     * @param[in]   nrf_error   Error code containing information about what went wrong.
     */
    static void nrf_qwr_error_handler(uint32_t nrf_error)
    {
        APP_ERROR_HANDLER(nrf_error);
    }
    
    
    /**@brief Function for handling the data from the Nordic UART Service.
     *
     * @details This function will process the data received from the Nordic UART BLE Service and send
     *          it to the UART module.
     *
     * @param[in] p_evt       Nordic UART Service event.
     */
    /**@snippet [Handling the data received over BLE] */
    static void nus_data_handler(ble_nus_evt_t * p_evt)
    {
    
        if (p_evt->type == BLE_NUS_EVT_RX_DATA)
        {
            uint32_t err_code;
    
            NRF_LOG_DEBUG("Received data from BLE NUS. Writing data on UART.");
            NRF_LOG_HEXDUMP_DEBUG(p_evt->params.rx_data.p_data, p_evt->params.rx_data.length);
    
            for (uint32_t i = 0; i < p_evt->params.rx_data.length; i++)
            {
                do
                {
                    err_code = app_uart_put(p_evt->params.rx_data.p_data[i]);
                    if ((err_code != NRF_SUCCESS) && (err_code != NRF_ERROR_BUSY))
                    {
                        NRF_LOG_ERROR("Failed receiving NUS message. Error 0x%x. ", err_code);
                        APP_ERROR_CHECK(err_code);
                    }
                } while (err_code == NRF_ERROR_BUSY);
            }
            if (p_evt->params.rx_data.p_data[p_evt->params.rx_data.length - 1] == '\r')
            {
                while (app_uart_put('\n') == NRF_ERROR_BUSY);
            }
        }
    
    }
    /**@snippet [Handling the data received over BLE] */
    
    
    /**@brief Function for initializing services that will be used by the application.
     */
    static void services_init(void)
    {
        uint32_t           err_code;
        ble_nus_init_t     nus_init;
        nrf_ble_qwr_init_t qwr_init = {0};
    
        // Initialize Queued Write Module.
        qwr_init.error_handler = nrf_qwr_error_handler;
    
        err_code = nrf_ble_qwr_init(&m_qwr, &qwr_init);
        APP_ERROR_CHECK(err_code);
    
        // Initialize NUS.
        memset(&nus_init, 0, sizeof(nus_init));
        // SEC_JUST_WORKS?
    
        nus_init.data_handler = nus_data_handler;
    
        err_code = ble_nus_init(&m_nus, &nus_init);
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for handling an event from the Connection Parameters Module.
     *
     * @details This function will be called for all events in the Connection Parameters Module
     *          which are passed to the application.
     *
     * @note All this function does is to disconnect. This could have been done by simply setting
     *       the disconnect_on_fail config parameter, but instead we use the event handler
     *       mechanism to demonstrate its use.
     *
     * @param[in] p_evt  Event received from the Connection Parameters Module.
     */
    static void on_conn_params_evt(ble_conn_params_evt_t * p_evt)
    {
        uint32_t err_code;
    
        if (p_evt->evt_type == BLE_CONN_PARAMS_EVT_FAILED)
        {
            err_code = sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_CONN_INTERVAL_UNACCEPTABLE);
            APP_ERROR_CHECK(err_code);
        }
    }
    
    
    /**@brief Function for handling errors from the Connection Parameters module.
     *
     * @param[in] nrf_error  Error code containing information about what went wrong.
     */
    static void conn_params_error_handler(uint32_t nrf_error)
    {
        APP_ERROR_HANDLER(nrf_error);
    }
    
    
    /**@brief Function for initializing the Connection Parameters module.
     */
    static void conn_params_init(void)
    {
        uint32_t               err_code;
        ble_conn_params_init_t cp_init;
    
        memset(&cp_init, 0, sizeof(cp_init));
    
        cp_init.p_conn_params                  = NULL;
        cp_init.first_conn_params_update_delay = FIRST_CONN_PARAMS_UPDATE_DELAY;
        cp_init.next_conn_params_update_delay  = NEXT_CONN_PARAMS_UPDATE_DELAY;
        cp_init.max_conn_params_update_count   = MAX_CONN_PARAMS_UPDATE_COUNT;
        cp_init.start_on_notify_cccd_handle    = BLE_GATT_HANDLE_INVALID;
        cp_init.disconnect_on_fail             = false;
        cp_init.evt_handler                    = on_conn_params_evt;
        cp_init.error_handler                  = conn_params_error_handler;
    
        err_code = ble_conn_params_init(&cp_init);
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for putting the chip into sleep mode.
     *
     * @note This function will not return.
     */
    static void sleep_mode_enter(void)
    {
        uint32_t err_code = bsp_indication_set(BSP_INDICATE_IDLE);
        APP_ERROR_CHECK(err_code);
    
        // Prepare wakeup buttons.
        err_code = bsp_btn_ble_sleep_mode_prepare();
        APP_ERROR_CHECK(err_code);
    
        // Go to system-off mode (this function will not return; wakeup will cause a reset).
        err_code = sd_power_system_off();
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for handling advertising events.
     *
     * @details This function will be called for advertising events which are passed to the application.
     *
     * @param[in] ble_adv_evt  Advertising event.
     */
    static void on_adv_evt(ble_adv_evt_t ble_adv_evt)
    {
        uint32_t err_code;
    
        switch (ble_adv_evt)
        {
            case BLE_ADV_EVT_FAST:
                NRF_LOG_INFO("Fast advertising");
                err_code = bsp_indication_set(BSP_INDICATE_ADVERTISING);
                APP_ERROR_CHECK(err_code);
                break;
            case BLE_ADV_EVT_IDLE:
                sleep_mode_enter();
                break;
            default:
                break;
        }
    }
    
    
    /**@brief Function for handling BLE events.
     *
     * @param[in]   p_ble_evt   Bluetooth stack event.
     * @param[in]   p_context   Unused.
     */
    static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
    {
        uint32_t err_code;
    
        pm_handler_secure_on_connection(p_ble_evt);
    
        switch (p_ble_evt->header.evt_id)
        {
            case BLE_GAP_EVT_DISCONNECTED:
                NRF_LOG_INFO("Disconnected");
                m_conn_handle = BLE_CONN_HANDLE_INVALID;
                // Check if the last connected peer had not used MITM, if so, delete its bond information.
                if (m_peer_to_be_deleted != PM_PEER_ID_INVALID)
                {
                    err_code = pm_peer_delete(m_peer_to_be_deleted);
                    APP_ERROR_CHECK(err_code);
                    NRF_LOG_DEBUG("Collector's bond deleted");
                    m_peer_to_be_deleted = PM_PEER_ID_INVALID;
                }
                break;
    
            case BLE_GAP_EVT_CONNECTED:
                NRF_LOG_INFO("Connected");
                m_peer_to_be_deleted = PM_PEER_ID_INVALID;
                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 = nrf_ble_qwr_conn_handle_assign(&m_qwr, m_conn_handle);
                APP_ERROR_CHECK(err_code);
    	    /* needed ?
                err_code = pm_conn_secure(p_ble_evt->evt.gap_evt.conn_handle, false);
                if (err_code != NRF_ERROR_BUSY)
                {
                    APP_ERROR_CHECK(err_code);
                }
    	    */
                break;
    
            case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
            {
                NRF_LOG_DEBUG("PHY update request.");
                ble_gap_phys_t const phys =
                {
                    .rx_phys = BLE_GAP_PHY_AUTO,
                    .tx_phys = BLE_GAP_PHY_AUTO,
                };
                err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
                APP_ERROR_CHECK(err_code);
            } break;
    
            case BLE_GATTC_EVT_TIMEOUT:
                // Disconnect on GATT Client timeout event.
                err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gattc_evt.conn_handle,
                                                 BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
                APP_ERROR_CHECK(err_code);
                break;
    
            case BLE_GATTS_EVT_TIMEOUT:
                // Disconnect on GATT Server timeout event.
                err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gatts_evt.conn_handle,
                                                 BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
                APP_ERROR_CHECK(err_code);
                break;
    
            case BLE_GAP_EVT_PASSKEY_DISPLAY:
            {
                char passkey[PASSKEY_LENGTH + 1];
                memcpy(passkey, p_ble_evt->evt.gap_evt.params.passkey_display.passkey, PASSKEY_LENGTH);
                passkey[PASSKEY_LENGTH] = 0;
    
                NRF_LOG_INFO("Passkey: %s", nrf_log_push(passkey));
            } break;
            
            case BLE_GAP_EVT_AUTH_KEY_REQUEST:
                NRF_LOG_INFO("BLE_GAP_EVT_AUTH_KEY_REQUEST");
                break;
    
            case BLE_GAP_EVT_LESC_DHKEY_REQUEST:
                NRF_LOG_INFO("BLE_GAP_EVT_LESC_DHKEY_REQUEST");
                break;
    
             case BLE_GAP_EVT_AUTH_STATUS:
                 NRF_LOG_INFO("BLE_GAP_EVT_AUTH_STATUS: status=0x%x bond=0x%x lv4: %d kdist_own:0x%x kdist_peer:0x%x",
                              p_ble_evt->evt.gap_evt.params.auth_status.auth_status,
                              p_ble_evt->evt.gap_evt.params.auth_status.bonded,
                              p_ble_evt->evt.gap_evt.params.auth_status.sm1_levels.lv4,
                              *((uint8_t *)&p_ble_evt->evt.gap_evt.params.auth_status.kdist_own),
                              *((uint8_t *)&p_ble_evt->evt.gap_evt.params.auth_status.kdist_peer));
                break;
    
            default:
                // No implementation needed.
                break;
        }
    }
    
    
    /**@brief Function for the SoftDevice initialization.
     *
     * @details This function initializes the SoftDevice and the BLE event interrupt.
     */
    static void ble_stack_init(void)
    {
        ret_code_t err_code;
    
        err_code = nrf_sdh_enable_request();
        APP_ERROR_CHECK(err_code);
    
        // Configure the BLE stack using the default settings.
        // Fetch the start address of the application RAM.
        uint32_t ram_start = 0;
        err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Enable BLE stack.
        err_code = nrf_sdh_ble_enable(&ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Register a handler for BLE events.
        NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
    }
    
    
    /**@brief Function for handling events from the BSP module.
     *
     * @param[in]   event   Event generated by button press.
     */
    void bsp_event_handler(bsp_event_t event)
    {
        uint32_t err_code;
        switch (event)
        {
            case BSP_EVENT_SLEEP:
                sleep_mode_enter();
                break;
    
            case BSP_EVENT_DISCONNECT:
                err_code = sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
                if (err_code != NRF_ERROR_INVALID_STATE)
                {
                    APP_ERROR_CHECK(err_code);
                }
                break;
    
            case BSP_EVENT_WHITELIST_OFF:
                if (m_conn_handle == BLE_CONN_HANDLE_INVALID)
                {
                    err_code = ble_advertising_restart_without_whitelist(&m_advertising);
                    if (err_code != NRF_ERROR_INVALID_STATE)
                    {
                        APP_ERROR_CHECK(err_code);
                    }
                }
                break;
    
            default:
                break;
        }
    }
    
    /**@brief Function for the Peer Manager initialization.
     */
    
    static void peer_manager_init(void)
    {
        ble_gap_sec_params_t sec_param;
        ret_code_t           err_code;
    
        err_code = pm_init();
        APP_ERROR_CHECK(err_code);
    
        memset(&sec_param, 0, sizeof(ble_gap_sec_params_t));
    
        // Security parameters to be used for all security procedures.
        sec_param.bond           = SEC_PARAM_BOND;
        sec_param.mitm           = SEC_PARAM_MITM;
        sec_param.lesc           = SEC_PARAM_LESC;
        sec_param.keypress       = SEC_PARAM_KEYPRESS;
        sec_param.io_caps        = SEC_PARAM_IO_CAPABILITIES;
        sec_param.oob            = SEC_PARAM_OOB;
        sec_param.min_key_size   = SEC_PARAM_MIN_KEY_SIZE;
        sec_param.max_key_size   = SEC_PARAM_MAX_KEY_SIZE;
        sec_param.kdist_own.enc  = 1;
        sec_param.kdist_own.id   = 1;
        sec_param.kdist_peer.enc = 1;
        sec_param.kdist_peer.id  = 1;
    
        err_code = pm_sec_params_set(&sec_param);
        APP_ERROR_CHECK(err_code);
    
        err_code = pm_register(pm_evt_handler);
        APP_ERROR_CHECK(err_code);
    }
    
    static void delete_bonds(void)
    {
        ret_code_t err_code;
    
        NRF_LOG_INFO("Erase bonds!");
    
        err_code = pm_peers_delete();
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for initializing the Advertising functionality.
     */
    static void advertising_init(void)
    {
        uint32_t               err_code;
        ble_advertising_init_t init;
    
        memset(&init, 0, sizeof(init));
    
        init.advdata.name_type          = BLE_ADVDATA_FULL_NAME;
        init.advdata.include_appearance = true;
        init.advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_LIMITED_DISC_MODE;
        init.srdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
        init.srdata.uuids_complete.p_uuids  = m_adv_uuids;
    
        init.config.ble_adv_fast_enabled  = true;
        init.config.ble_adv_fast_interval = APP_ADV_INTERVAL;
        init.config.ble_adv_fast_timeout  = APP_ADV_DURATION;
        init.evt_handler = on_adv_evt;
    
        err_code = ble_advertising_init(&m_advertising, &init);
        APP_ERROR_CHECK(err_code);
    
        ble_advertising_conn_cfg_tag_set(&m_advertising, APP_BLE_CONN_CFG_TAG);
    }
    
    /**@brief Function for initializing buttons and leds.
     *
     * @param[out] p_erase_bonds  Will be true if the clear bonding button was pressed to wake the application up.
     */
    static void buttons_leds_init(bool * p_erase_bonds)
    {
        bsp_event_t startup_event;
    
        uint32_t err_code = bsp_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS, bsp_event_handler);
        APP_ERROR_CHECK(err_code);
    
        err_code = bsp_btn_ble_init(NULL, &startup_event);
        APP_ERROR_CHECK(err_code);
    
        *p_erase_bonds = (startup_event == BSP_EVENT_CLEAR_BONDING_DATA);
    }
    
    
    /**@brief Function for initializing the nrf log module.
     */
    static void log_init(void)
    {
        ret_code_t err_code = NRF_LOG_INIT(NULL);
        APP_ERROR_CHECK(err_code);
    
        NRF_LOG_DEFAULT_BACKENDS_INIT();
    }
    
    
    /**@brief Function for initializing power management.
     */
    static void power_management_init(void)
    {
        ret_code_t err_code;
        err_code = nrf_pwr_mgmt_init();
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@brief Function for handling the idle state (main loop).
     *
     * @details If there is no pending log operation, then sleep until next the next event occurs.
     */
    static void idle_state_handle(void)
    {
        ret_code_t err_code;
    
        err_code = nrf_ble_lesc_request_handler();
        APP_ERROR_CHECK(err_code);
    
        if (NRF_LOG_PROCESS() == false)
        {
            nrf_pwr_mgmt_run();
        }
    }
    
    
    /**@brief   Function for handling app_uart events.
     *
     * @details This function will receive a single character from the app_uart module and append it to
     *          a string. The string will be be sent over BLE when the last character received was a
     *          'new line' '\n' (hex 0x0A) or if the string has reached the maximum data length.
     */
    /**@snippet [Handling the data received over UART] */
    void uart_event_handle(app_uart_evt_t * p_event)
    {
        static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
        static uint8_t index = 0;
        uint32_t       err_code;
    
        switch (p_event->evt_type)
        {
            case APP_UART_DATA_READY:
                UNUSED_VARIABLE(app_uart_get(&data_array[index]));
                index++;
    
                if ((data_array[index - 1] == '\n') ||
                    (data_array[index - 1] == '\r') ||
                    (index >= m_ble_nus_max_data_len))
                {
                    if (index > 1)
                    {
                        NRF_LOG_DEBUG("Ready to send data over BLE NUS");
                        NRF_LOG_HEXDUMP_DEBUG(data_array, index);
    
                        do
                        {
                            uint16_t length = (uint16_t)index;
                            err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
                            if ((err_code != NRF_ERROR_INVALID_STATE) &&
                                (err_code != NRF_ERROR_RESOURCES) &&
                                (err_code != NRF_ERROR_NOT_FOUND))
                            {
                                APP_ERROR_CHECK(err_code);
                            }
                        } while (err_code == NRF_ERROR_RESOURCES);
                    }
    
                    index = 0;
                }
                break;
    
            case APP_UART_COMMUNICATION_ERROR:
                APP_ERROR_HANDLER(p_event->data.error_communication);
                break;
    
            case APP_UART_FIFO_ERROR:
                APP_ERROR_HANDLER(p_event->data.error_code);
                break;
    
            default:
                break;
        }
    }
    /**@snippet [Handling the data received over UART] */
    
    
    /**@brief  Function for initializing the UART module.
     */
    /**@snippet [UART Initialization] */
    static void uart_init(void)
    {
        uint32_t                     err_code;
        app_uart_comm_params_t const comm_params =
        {
            .rx_pin_no    = RX_PIN_NUMBER,
            .tx_pin_no    = TX_PIN_NUMBER,
            .rts_pin_no   = RTS_PIN_NUMBER,
            .cts_pin_no   = CTS_PIN_NUMBER,
            .flow_control = APP_UART_FLOW_CONTROL_DISABLED,
            .use_parity   = false,
    #if defined (UART_PRESENT)
            .baud_rate    = NRF_UART_BAUDRATE_115200
    #else
            .baud_rate    = NRF_UARTE_BAUDRATE_115200
    #endif
        };
    
        APP_UART_FIFO_INIT(&comm_params,
                           UART_RX_BUF_SIZE,
                           UART_TX_BUF_SIZE,
                           uart_event_handle,
                           APP_IRQ_PRIORITY_LOWEST,
                           err_code);
        APP_ERROR_CHECK(err_code);
    }
    /**@snippet [UART Initialization] */
    
    
    
    
    /**@brief Function for starting advertising.
     */
    static void advertising_start(bool erase_bonds)
    {
        if (erase_bonds == true)
        {
            delete_bonds();
            // Advertising is started by PM_EVT_PEERS_DELETE_SUCCEEDED event.
        }
        else
        {
            ret_code_t err_code;
    
            err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);
            APP_ERROR_CHECK(err_code);
        }
    }
    
    
    
    
    
    /**@brief Application main function.
     */
    int main(void)
    {
        bool erase_bonds;
    
        // Initialize.
        uart_init();
        log_init();
        timers_init();
        buttons_leds_init(&erase_bonds);
        power_management_init();
        ble_stack_init();
        gap_params_init();
        gatt_init();
        services_init();
        advertising_init();
        conn_params_init();
    
        peer_manager_init();
    
    
        // Start execution.
        printf("\r\nUART started.\r\n");
        NRF_LOG_INFO("Debug logging for UART over RTT started.");
        advertising_start(erase_bonds);
    
        // Enter main loop.
        for (;;)
        {
            idle_state_handle();
        }
    }
    
    
    /**
     * @}
     */
    

    This works, but still no pairing/bonding!
    Here a few questions about my port.

    In services_init of ble_app_gls there is:
         // Here the sec level for the Glucose Service can be changed/increased.
         gls_init.gl_meas_cccd_wr_sec = SEC_JUST_WORKS;
    There are no such fields in ble_nus_init_t. Is this relevant? I guess not because there is mentioning of "changed/increased" and not of initialize/configure.

    In the ble_evt_handler of ble_app_gls there is NO call to pm_conn_secure.
    I thought that this was needed (see peer manager functionality documentation).
    I thought that encryption was enabled via SEC_PARAM_LESC.

    Finally here a short RTT log:

        <info> app_timer: RTC: initialized.
        <debug> nrf_ble_lesc: Initialized nrf_crypto.
        <debug> nrf_ble_lesc: Initialized nrf_ble_lesc.
        <debug> nrf_ble_lesc: Generating ECC key pair
        <info> app: Debug logging for UART over RTT started.
        <info> app: Fast advertising
        <debug> nrf_ble_gatt: Requesting to update ATT MTU to 247 bytes on connection 0x0.
        <debug> nrf_ble_gatt: Updating data length to 251 on connection 0x0.
        <info> app: --> pm_evt_handler 1
        <info> app: --> PM_EVT_CONN_SEC_PARAMS_REQ
       <info> app: Connected
       <debug> nrf_ble_gatt: Data length updated to 251 on connection 0x0.
       <debug> nrf_ble_gatt: max_rx_octets: 251
       <debug> nrf_ble_gatt: max_tx_octets: 251
       <debug> nrf_ble_gatt: max_rx_time: 2120
       <debug> nrf_ble_gatt: max_tx_time: 2120
        0xF7
       <debug> nrf_ble_gatt: ATT MTU updated to 247 bytes on connection 0x0 (response).
       <info> app: Data len is set to 0xF4(244)
       <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7
       <debug> nrf_ble_gatt: Peer on connection 0x0 requested an ATT MTU of 517 bytes.
       <debug> nrf_ble_gatt: Updating ATT MTU to 247 bytes (desired: 247) on connection 0x0.
       <info> app: Data len is set to 0xF4(244)
       <debug> app: ATT MTU exchange completed. central 0xF7 peripheral 0xF7

    I seemed to have missed something, but what?

    Thanks again,
    Sietse

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