How to build a maximum-length beacon (without using extended advertising)?

[Pierre Landau]

The discussion in https://devzone.nordicsemi.com/f/nordic-q-a/79364/maximum-number-of-bytes-that-can-be-used-in-beacon-advertising suggests that we should be able to populate 27 bytes of a beacon, with the remainder consisting of Manufacturer ID, length, and a type byte.  However, none of the examples suggest how to actually do this. we were using extended beacons but ran into a use case where the recipient only had BLE 4.2 so now it's about how many bytes we can squeeze out of traditional beacons...

My experiments with using ble_advdata_manuf_data_t and calling ble_data_encode() suggest that I can only directly affect the contents of a much smaller number of bytes without getting an NRF_ERROR_DATA_SIZE error.

I then tried just manually put in the 2 bytes of Manufacturer ID, a type (??) and a length (31 or 27?) then put in data, without calling ble_data_encode(). What I got back was BLE_ERROR_GAP_UUID_LIST_MISMATCH, so apparently that's not quite the correct approach.  Suggestions would be most welcome.

Thanks!

[Einar Thorsrud]

Hi,

The maximum size of the manufacturer specific data in a normal advertising packet is 24 bytes. With this, the entire advertising packet will be 31 bytes, which is the maximum. You can refer to this code which is a stripped down version of the beacon example that just use a maximum sized manufacturer specific array (you can drop it into the beacon example in SDK 17.1.0 to test yourself).

Fullscreen 0572.main.c Download

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/** @file
 *
 * @defgroup ble_sdk_app_beacon_main main.c
 * @{
 * @ingroup ble_sdk_app_beacon
 * @brief Beacon Transmitter Sample Application main file.
 *
 * This file contains the source code for an Beacon transmitter sample application.
 */

#include <stdbool.h>
#include <stdint.h>
#include "nordic_common.h"
#include "bsp.h"
#include "nrf_soc.h"
#include "nrf_sdh.h"
#include "nrf_sdh_ble.h"
#include "ble_advdata.h"
#include "app_timer.h"
#include "nrf_pwr_mgmt.h"

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

#define APP_COMPANY_IDENTIFIER 0x0059                                      /**< Company identifier for Nordic Semiconductor ASA. as per www.bluetooth.org. */
#define MANUF_DATA_LENGTH               24
#define APP_BLE_CONN_CFG_TAG            1                                  /**< A tag identifying the SoftDevice BLE configuration. */

#define NON_CONNECTABLE_ADV_INTERVAL    MSEC_TO_UNITS(100, UNIT_0_625_MS)  /**< The advertising interval for non-connectable advertisement (100 ms). This value can vary between 100ms to 10.24s). */

#define APP_BEACON_INFO_LENGTH          0x17                               /**< Total length of information advertised by the Beacon. */
#define APP_ADV_DATA_LENGTH             0x15                               /**< Length of manufacturer specific data in the advertisement. */

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


static ble_gap_adv_params_t m_adv_params;                                  /**< Parameters to be passed to the stack when starting advertising. */
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. */

/**@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 = NULL,
        .len    = 0

    }
};

/**@brief Dummy manufacturer specific data */
static uint8_t m_manuf_data[MANUF_DATA_LENGTH] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17
};

/**@brief Callback function for asserts in the SoftDevice.
 *
 * @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]   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 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)
{
    uint32_t      err_code;
    ble_advdata_t advdata;
    uint8_t       flags = BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED;

    ble_advdata_manuf_data_t manuf_specific_data;

    manuf_specific_data.company_identifier = APP_COMPANY_IDENTIFIER;

    manuf_specific_data.data.p_data = (uint8_t *) m_manuf_data;
    manuf_specific_data.data.size   = MANUF_DATA_LENGTH;

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

    advdata.name_type             = BLE_ADVDATA_NO_NAME;
    advdata.flags                 = flags;
    advdata.p_manuf_specific_data = &manuf_specific_data;

    // Initialize advertising parameters (used when starting advertising).
    memset(&m_adv_params, 0, sizeof(m_adv_params));

    m_adv_params.properties.type = BLE_GAP_ADV_TYPE_NONCONNECTABLE_NONSCANNABLE_UNDIRECTED;
    m_adv_params.p_peer_addr     = NULL;    // Undirected advertisement.
    m_adv_params.filter_policy   = BLE_GAP_ADV_FP_ANY;
    m_adv_params.interval        = NON_CONNECTABLE_ADV_INTERVAL;
    m_adv_params.duration        = 0;       // Never time out.

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

    NRF_LOG_INFO("Advertising data length after encoding: %u", m_adv_data.adv_data.len);

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &m_adv_params);
    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);

    err_code = bsp_indication_set(BSP_INDICATE_ADVERTISING);
    APP_ERROR_CHECK(err_code);
}


/**@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;

    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);
}


/**@brief Function for initializing logging. */
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 LEDs. */
static void leds_init(void)
{
    ret_code_t err_code = bsp_init(BSP_INIT_LEDS, NULL);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing timers. */
static void timers_init(void)
{
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);
}


/**@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();
    timers_init();
    leds_init();
    power_management_init();
    ble_stack_init();
    advertising_init();

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

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


/**
 * @}
 */