RE: Onboard LED blinks and nrf52840 does not advertise

stationarydev — Thu, 30 Sep 2021 09:45:41 GMT
I have LEDs connected to pins 3, 4 & 5.

Not sure if you've noticed my message updates, but it seems like the nrf_sdh_ble_enable call only fails when l2cap_conn_cfg.ch_count is non-zero.
I will build the ipsp acceptor and see how that works out.
RE: Onboard LED blinks and nrf52840 does not advertise

Simonr — Thu, 30 Sep 2021 08:36:58 GMT
Okay, I just assumed you were working on an nRF52840 DK. A less comprehensive L2CAP example is the IPSP acceptor example I think, which just demonstrates the usage of an L2CAP connection oriented channel. Do you know what pin on the nRF52840 the LED is connected to?
Best regards,
Simon
RE: Onboard LED blinks and nrf52840 does not advertise

stationarydev — Thu, 30 Sep 2021 07:05:03 GMT
I just checked, and it seems to restart after the call to nrf_sdh_ble_enable when I'm configuring the l2cap connections.
UPDATE: It looks like it's failing with NRF_ERROR_NO_MEM.
UPDATE: The call to nrf_sdh_ble_enable doesn't fail when I set the ch_count on l2cap_conn_cfg to 0 instead of 1.
RE: Onboard LED blinks and nrf52840 does not advertise

stationarydev — Wed, 29 Sep 2021 18:17:07 GMT
It's the only programmable on board LED. I'm using the Sparkfun Pro nRF52840 Mini. Here's the whole code.
/**
 * Copyright (c) 2015 - 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
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * 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.
 *
 */
/**
 * @brief Blinky Sample Application main file.
 *
 * This file contains the source code for a sample server application using the LED Button service.
 */

#include <stdint.h>
#include <string.h>
#include "nordic_common.h"
#include "nrf.h"
#include "app_error.h"
#include "ble.h"
#include "ble_l2cap.h"
#include "ble_types.h"
#include "ble_err.h"
#include "ble_hci.h"
#include "ble_srv_common.h"
#include "ble_advdata.h"
#include "ble_conn_params.h"
#include "nrf_delay.h"
#include "nrf_sdh.h"
#include "nrf_sdh_ble.h"
#include "boards.h"
#include "app_timer.h"
#include "app_button.h"
#include "ble_lbs.h"
#include "nrf_ble_gatt.h"
#include "nrf_ble_qwr.h"
#include "nrf_pwr_mgmt.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"


#define MY_GPIO_PIN_1  NRF_GPIO_PIN_MAP(0, 3)
#define MY_GPIO_PIN_2  NRF_GPIO_PIN_MAP(0, 4)
#define MY_GPIO_PIN_3 NRF_GPIO_PIN_MAP(0, 5)

#define ADVERTISING_LED                 BSP_BOARD_LED_0                         /**< Is on when device is advertising. */
#define CONNECTED_LED                   MY_GPIO_PIN_1                         /**< Is on when device has connected. */
#define LEDBUTTON_LED                   MY_GPIO_PIN_2                         /**< LED to be toggled with the help of the LED Button Service. */
#define CHANNEL_DATA_LED                MY_GPIO_PIN_3 // To be on when data is recvd on l2cap channel
#define LEDBUTTON_BUTTON                BSP_BUTTON_0                            /**< Button that will trigger the notification event with the LED Button Service */

#define DEVICE_NAME                     "Super_Blinky"                         /**< Name of device. Will be included in the advertising data. */

#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                BLE_GAP_ADV_TIMEOUT_GENERAL_UNLIMITED   /**< The advertising time-out (in units of seconds). When set to 0, we will never time out. */


#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(100, UNIT_1_25_MS)        /**< Minimum acceptable connection interval (0.5 seconds). */
#define MAX_CONN_INTERVAL               MSEC_TO_UNITS(200, UNIT_1_25_MS)        /**< Maximum acceptable connection interval (1 second). */
#define SLAVE_LATENCY                   0                                       /**< Slave latency. */
#define CONN_SUP_TIMEOUT                MSEC_TO_UNITS(4000, UNIT_10_MS)         /**< Connection supervisory time-out (4 seconds). */

#define FIRST_CONN_PARAMS_UPDATE_DELAY  APP_TIMER_TICKS(20000)                  /**< Time from initiating event (connect or start of notification) to first time sd_ble_gap_conn_param_update is called (15 seconds). */
#define NEXT_CONN_PARAMS_UPDATE_DELAY   APP_TIMER_TICKS(5000)                   /**< Time between each call to sd_ble_gap_conn_param_update after the first call (5 seconds). */
#define MAX_CONN_PARAMS_UPDATE_COUNT    3                                       /**< Number of attempts before giving up the connection parameter negotiation. */

#define BUTTON_DETECTION_DELAY          APP_TIMER_TICKS(50)                     /**< Delay from a GPIOTE event until a button is reported as pushed (in number of timer ticks). */

#define DEAD_BEEF                       0xDEADBEEF                              /**< Value used as error code on stack dump, can be used to identify stack location on stack unwind. */
#define L2CAP_SDU_BUF_SIZE 1024

#define L2CAP_RX_MPS                         200                                /**< Size of L2CAP Rx MPS (must be at least BLE_L2CAP_MPS_MIN).*/
#define L2CAP_TX_MPS                         200                                /**< Size of L2CAP Tx MPS (must be at least BLE_L2CAP_MPS_MIN).*/


BLE_LBS_DEF(m_lbs);                                                             /**< LED Button Service instance. */
NRF_BLE_GATT_DEF(m_gatt);                                                       /**< GATT module instance. */
NRF_BLE_QWR_DEF(m_qwr);                                                         /**< Context for the Queued Write module.*/

static uint16_t m_conn_handle = BLE_CONN_HANDLE_INVALID;                        /**< Handle of the current connection. */

static uint8_t m_adv_handle = BLE_GAP_ADV_SET_HANDLE_NOT_SET;                   /**< Advertising handle used to identify an advertising set. */
static uint8_t m_enc_advdata[BLE_GAP_ADV_SET_DATA_SIZE_MAX];                    /**< Buffer for storing an encoded advertising set. */
static uint8_t m_enc_scan_response_data[BLE_GAP_ADV_SET_DATA_SIZE_MAX];         /**< Buffer for storing an encoded scan data. */
static uint8_t m_l2cap_sdu_buf[L2CAP_SDU_BUF_SIZE];         /**< Buffer for storing an encoded scan data. */

static ble_data_t const sdu_buf = {
  .len = L2CAP_SDU_BUF_SIZE,
  .p_data = m_l2cap_sdu_buf
};

/**@brief Struct that contains pointers to the encoded advertising data. */
static ble_gap_adv_data_t m_adv_data =
{
    .adv_data =
    {
        .p_data = m_enc_advdata,
        .len    = BLE_GAP_ADV_SET_DATA_SIZE_MAX
    },
    .scan_rsp_data =
    {
        .p_data = m_enc_scan_response_data,
        .len    = BLE_GAP_ADV_SET_DATA_SIZE_MAX

    }
};

static void led_on(uint8_t led)
{
    nrf_gpio_pin_write(led, 1);
}

static void led_off(uint8_t led)
{
    nrf_gpio_pin_write(led, 0);
}

/**@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 analyze
 *          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 the LEDs initialization.
 *
 * @details Initializes all LEDs used by the application.
 */
static void leds_init(void)
{
    bsp_board_init(BSP_INIT_LEDS);
    nrf_gpio_cfg_output(MY_GPIO_PIN_1);
    nrf_gpio_cfg_output(MY_GPIO_PIN_2);
    nrf_gpio_cfg_output(MY_GPIO_PIN_3);
}


/**@brief Function for the Timer initialization.
 *
 * @details Initializes the timer module.
 */
static void timers_init(void)
{
    // Initialize timer module, making it use the scheduler
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for the GAP initialization.
 *
 * @details This function sets up all the necessary GAP (Generic Access Profile) parameters of the
 *          device including the device name, appearance, and the preferred connection parameters.
 */
static void gap_params_init(void)
{
    ret_code_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);
}


/**@brief Function for initializing the GATT module.
 */
static void gatt_init(void)
{
    ret_code_t err_code = nrf_ble_gatt_init(&m_gatt, NULL);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the Advertising functionality.
 *
 * @details Encodes the required advertising data and passes it to the stack.
 *          Also builds a structure to be passed to the stack when starting advertising.
 */
static void advertising_init(void)
{
    ret_code_t    err_code;
    ble_advdata_t advdata;
    ble_advdata_t srdata;

    ble_uuid_t adv_uuids[] = {{LBS_UUID_SERVICE, m_lbs.uuid_type}};

    // Build and set advertising data.
    memset(&advdata, 0, sizeof(advdata));

    advdata.name_type          = BLE_ADVDATA_FULL_NAME;
    advdata.include_appearance = true;
    advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;


    memset(&srdata, 0, sizeof(srdata));
    srdata.uuids_complete.uuid_cnt = sizeof(adv_uuids) / sizeof(adv_uuids[0]);
    srdata.uuids_complete.p_uuids  = adv_uuids;

    err_code = ble_advdata_encode(&advdata, m_adv_data.adv_data.p_data, &m_adv_data.adv_data.len);
    APP_ERROR_CHECK(err_code);

    err_code = ble_advdata_encode(&srdata, m_adv_data.scan_rsp_data.p_data, &m_adv_data.scan_rsp_data.len);
    APP_ERROR_CHECK(err_code);

    ble_gap_adv_params_t adv_params;

    // Set advertising parameters.
    memset(&adv_params, 0, sizeof(adv_params));

    adv_params.primary_phy     = BLE_GAP_PHY_1MBPS;
    adv_params.duration        = APP_ADV_DURATION;
    adv_params.properties.type = BLE_GAP_ADV_TYPE_CONNECTABLE_SCANNABLE_UNDIRECTED;
    adv_params.p_peer_addr     = NULL;
    adv_params.filter_policy   = BLE_GAP_ADV_FP_ANY;
    adv_params.interval        = APP_ADV_INTERVAL;

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &adv_params);
    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 write events to the LED characteristic.
 *
 * @param[in] p_lbs     Instance of LED Button Service to which the write applies.
 * @param[in] led_state Written/desired state of the LED.
 */
static void led_write_handler(uint16_t conn_handle, ble_lbs_t * p_lbs, uint8_t led_state)
{
    if (led_state)
    {
        led_on(LEDBUTTON_LED);
        NRF_LOG_INFO("Received LED ON!");
    }
    else
    {
        led_off(LEDBUTTON_LED);
        NRF_LOG_INFO("Received LED OFF!");
    }
}


/**@brief Function for initializing services that will be used by the application.
 */
static void services_init(void)
{
    ret_code_t         err_code;
    ble_lbs_init_t     init     = {0};
    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 LBS.
    init.led_write_handler = led_write_handler;

    err_code = ble_lbs_init(&m_lbs, &init);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling the Connection Parameters Module.
 *
 * @details This function will be called for all events in the Connection Parameters Module that
 *          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)
{
    ret_code_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 a Connection Parameters error.
 *
 * @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)
{
    ret_code_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 starting advertising.
 */
static void advertising_start(void)
{
    ret_code_t           err_code;

    err_code = sd_ble_gap_adv_start(m_adv_handle, APP_BLE_CONN_CFG_TAG);
    APP_ERROR_CHECK(err_code);

    bsp_board_led_on(ADVERTISING_LED);
}

// From the experimental ble peripheral OTS example
static void on_l2cap_ch_rx(ble_evt_t const * const p_ble_evt)
{
    nrf_gpio_pin_write(CHANNEL_DATA_LED, 1);
    NRF_LOG_DEBUG("Bytes received: %i", p_ble_evt->evt.l2cap_evt.params.rx.sdu_len);
    NRF_LOG_HEXDUMP_DEBUG(p_ble_evt->evt.l2cap_evt.params.rx.sdu_buf.p_data,
                          p_ble_evt->evt.l2cap_evt.params.rx.sdu_len);

}

/**@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)
{
    ret_code_t err_code;

    uint16_t local_cid;

    ble_l2cap_ch_setup_params_t setup_params;

    switch (p_ble_evt->header.evt_id)
    {
       case BLE_L2CAP_EVT_CH_SETUP_REQUEST:
            nrf_gpio_pin_write(CHANNEL_DATA_LED, 1);
            local_cid = p_ble_evt->evt.l2cap_evt.local_cid;

            setup_params = (ble_l2cap_ch_setup_params_t) {
              .le_psm = p_ble_evt->evt.l2cap_evt.params.ch_setup_request.le_psm,
              .status = BLE_L2CAP_CH_STATUS_CODE_SUCCESS,
              .rx_params = {
                .rx_mtu = p_ble_evt->evt.l2cap_evt.params.ch_setup_request.tx_params.tx_mtu,
                .rx_mps = p_ble_evt->evt.l2cap_evt.params.ch_setup_request.tx_params.tx_mps,
                .sdu_buf = sdu_buf
              }
            };

            if (NRF_SUCCESS != sd_ble_l2cap_ch_setup(p_ble_evt->evt.l2cap_evt.conn_handle, &local_cid, &setup_params))
              break;

            break;

        case BLE_L2CAP_EVT_CH_RX:
            NRF_LOG_DEBUG("BLE_L2CAP_EVT_CH_RX");
            on_l2cap_ch_rx(p_ble_evt);
            break;

        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected");
            led_on(CONNECTED_LED);
            bsp_board_led_off(ADVERTISING_LED);
            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);
            err_code = app_button_enable();
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected");
            led_off(CONNECTED_LED);
            m_conn_handle = BLE_CONN_HANDLE_INVALID;
            err_code = app_button_disable();
            APP_ERROR_CHECK(err_code);
            advertising_start();
            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);
            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_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_GATTC_EVT_TIMEOUT:
            // Disconnect on GATT Client timeout event.
            NRF_LOG_DEBUG("GATT Client Timeout.");
            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.
            NRF_LOG_DEBUG("GATT Server Timeout.");
            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;

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


/**@brief Function for initializing the BLE stack.
 *
 * @details Initializes the SoftDevice and the BLE event interrupt.
 */
static void ble_stack_init(void)
{
    ret_code_t err_code;
    ble_cfg_t ble_cfg;

    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);

    if (false) {
      memset(&ble_cfg, 0x00, sizeof(ble_cfg));
      // Set l2cap channel configuration
      ble_cfg.conn_cfg.conn_cfg_tag                        = APP_BLE_CONN_CFG_TAG;
      ble_cfg.conn_cfg.params.l2cap_conn_cfg.rx_mps        = L2CAP_RX_MPS;
      ble_cfg.conn_cfg.params.l2cap_conn_cfg.rx_queue_size = 1;
      ble_cfg.conn_cfg.params.l2cap_conn_cfg.tx_mps        = L2CAP_TX_MPS;
      ble_cfg.conn_cfg.params.l2cap_conn_cfg.tx_queue_size = 1;
      ble_cfg.conn_cfg.params.l2cap_conn_cfg.ch_count      = 1;

      err_code = sd_ble_cfg_set(BLE_CONN_CFG_L2CAP, &ble_cfg, 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 button handler module.
 *
 * @param[in] pin_no        The pin that the event applies to.
 * @param[in] button_action The button action (press/release).
 */
static void button_event_handler(uint8_t pin_no, uint8_t button_action)
{
    ret_code_t err_code;

    switch (pin_no)
    {
        case LEDBUTTON_BUTTON:
            NRF_LOG_INFO("Send button state change.");
            err_code = ble_lbs_on_button_change(m_conn_handle, &m_lbs, button_action);
            if (err_code != NRF_SUCCESS &&
                err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
                err_code != NRF_ERROR_INVALID_STATE &&
                err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING)
            {
                APP_ERROR_CHECK(err_code);
            }
            break;

        default:
            APP_ERROR_HANDLER(pin_no);
            break;
    }
}


/**@brief Function for initializing the button handler module.
 */
static void buttons_init(void)
{
    ret_code_t err_code;

    //The array must be static because a pointer to it will be saved in the button handler module.
    static app_button_cfg_t buttons[] =
    {
        {LEDBUTTON_BUTTON, false, BUTTON_PULL, button_event_handler}
    };

    err_code = app_button_init(buttons, ARRAY_SIZE(buttons),
                               BUTTON_DETECTION_DELAY);
    APP_ERROR_CHECK(err_code);
}


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)
{
    if (NRF_LOG_PROCESS() == false)
    {
        nrf_pwr_mgmt_run();
    }
}


/**@brief Function for application main entry.
 */
int main(void)
{
    // Initialize.
    log_init();
    leds_init();
    timers_init();
    buttons_init();
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    services_init();
    advertising_init();
    conn_params_init();

    // Start execution.
    NRF_LOG_INFO("Blinky example started.");
    advertising_start();

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


/**
 * @}
 */
The section of code in 'ble_stack_init' wrapped in an 'if (false)' is causing the device to stop advertising. I have been following the ots example as a guideline, but I'm starting from the ble_app_blinky example to keep things simple since I just need to accept arbitrary data on the l2cap channel.
RE: Onboard LED blinks and nrf52840 does not advertise

Simonr — Wed, 29 Sep 2021 13:17:45 GMT
What LED exactly is it that's blinking on the board? LED5 for instance is controlled by the onboard debugger MCU, and just indicates that the debugger is "alive and well".
Can you also upload the main() loop of your application so I can take a look at what the application starts out by doing? I would suggest referring to the Object Transfer Service example project in the SDK which supports establishing an L2CAP channel reserved for a specific service. Seems pretty close to what you're looking to do.
Best regards,
Simon