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BLE Service Sending When NFC Active

Hi

I have a really strange issue with an NRF52840. I'm using it with an MPU-9250 connected via TWI. I've modifed the excellent library:

https://github.com/Martinsbl/nrf5-mpu-examples

And have based my project on the nrf5-mpu-data-ready-interrupts example, with my own BLE custom Service and Characteristics.

All is working okay and data is being sent over BLE, only when I keep my hand close to the nrf52 (I assume its triggering the NFC sensor).

Any ideas, my code is attached, the reset is copied for the git-repository.

main.c

#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>

#include "nordic_common.h"
#include "nrf.h"
#include "app_error.h"
#include "ble.h"
#include "ble_hci.h"
#include "ble_srv_common.h"
#include "ble_advdata.h"
#include "ble_advertising.h"
#include "ble_conn_params.h"

//OPTION BLE Service
#include "srm_service.h"

#include "nrf_sdh.h"
#include "nrf_delay.h"
#include "nrf_sdh_soc.h"
#include "nrf_sdh_ble.h"
#include "app_timer.h"
#include "fds.h"
#include "peer_manager.h"
#include "bsp_btn_ble.h"
#include "sensorsim.h"
#include "ble_conn_state.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"

//MPU-9250
#include "nrf_drv_gpiote.h"
#include "app_mpu.h"
#define MPU_MPU_INT_PIN     30
volatile bool mpu_data_ready = false;

#define DEVICE_NAME "SRMotion"       /**< Name of device. Will be included in the advertising data. */
#define MANUFACTURER_NAME "StingRay" /**< Manufacturer. Will be passed to Device Information Service. */
#define APP_ADV_INTERVAL 300         /**< The advertising interval (in units of 0.625 ms. This value corresponds to 187.5 ms). */

#define APP_ADV_DURATION 18000  /**< The advertising duration (180 seconds) in units of 10 milliseconds. */
#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 MIN_CONN_INTERVAL MSEC_TO_UNITS(100, UNIT_1_25_MS) /**< Minimum acceptable connection interval (0.1 seconds). */
#define MAX_CONN_INTERVAL MSEC_TO_UNITS(200, UNIT_1_25_MS) /**< Maximum acceptable connection interval (0.2 second). */
#define SLAVE_LATENCY 0                                    /**< Slave latency. */
#define CONN_SUP_TIMEOUT MSEC_TO_UNITS(4000, UNIT_10_MS)   /**< Connection supervisory timeout (4 seconds). */

#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 0                               /**< Man In The Middle protection not required. */
#define SEC_PARAM_LESC 0                               /**< LE Secure Connections not 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. */

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

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. */

/* Declare all services  - BLE_XYZ_DEF(m_xyz); */
BLE_SRVC_OPT_DEF(m_srm_service);

//Advertised Services
static ble_uuid_t m_adv_uuids[] = /**< Universally unique service identifiers. */
    {
        {BLE_UUID_DEVICE_INFORMATION_SERVICE, BLE_UUID_TYPE_BLE},
        {BLE_SRM_SERVICE_UUID, BLE_UUID_TYPE_BLE},
};

//App Timers
#define SERVICES_NOTIFICATION_INTERVAL APP_TIMER_TICKS(5000) /**< Time between updating Services Characteristics. */
#define RAWData_GET_INTERVAL APP_TIMER_TICKS(1000)       /**< Time between updating RAW Data Characteristics. */
#define APP_TIMER_MAX_TIMERS 2;
APP_TIMER_DEF(m_service_notification_timer_id);
//APP_TIMER_DEF(m_rawdata_get_notification_timer_id);

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

static void advertising_start(bool erase_bonds);

//Device State
typedef uint8_t m_srm_state_evt_type_t;
enum
{
    SR_IDLE         = 0x00,
    SR_RUN          = 0x01,
    SR_FAULT_UKN    = 0x09,
    SR_FAULT_NO_MPU = 0xA1,
    SR_FAULT_MPU    = 0xA2,
    SR_FAULT_TWI    = 0xB1
};

typedef struct
{
    m_srm_state_evt_type_t evt_type;
} m_srm_state_type_t;
static m_srm_state_type_t m_srm_state;

//Device Command
typedef uint8_t m_srm_cmd_evt_type_t;
enum
{
    SR_STOP         = 0x00,
    SR_START        = 0x01,
};

typedef struct
{
    m_srm_cmd_evt_type_t evt_type;
} m_srm_cmd_type_t;
static m_srm_cmd_type_t m_cmd_state;


/**@brief Function for handling CMD request.
 */
static void handle_cmd_chr(ble_srvc_opt_t *p_service) {

    uint32_t err_code;

    ble_gatts_value_t	t_value;
    t_value.p_value = &m_cmd_state.evt_type;
	t_value.len      = 1;
	t_value.offset   = 0;

    err_code = sd_ble_gatts_value_get(p_service->conn_handle, p_service->cmd_char_handle.value_handle, &t_value);
    APP_ERROR_CHECK(err_code);
    
    switch (m_cmd_state.evt_type)
    {
    case SR_STOP:
        NRF_LOG_INFO("CMD Data = STOP");
        m_srm_state.evt_type = SR_IDLE;
        err_code = ble_srvc_set_state(p_service, m_srm_state.evt_type);
        APP_ERROR_CHECK(err_code);
        break;
    
    case SR_START:
        NRF_LOG_INFO("CMD Data = RUN");
        m_srm_state.evt_type = SR_RUN;
        err_code = ble_srvc_set_state(p_service, m_srm_state.evt_type);
        APP_ERROR_CHECK(err_code);
        break;

    default:
        NRF_LOG_INFO("CMD Data = UKN");
        break;
    }

}

/**@brief Function for handling SRM BLE Service events.
 */
static void on_ble_srm_service_evt(ble_srvc_opt_t *p_cus_service, ble_srvc_opt_evt_t *p_evt)
{
    //m_setget t_value;
    uint32_t err_code;

    switch (p_evt->evt_type)
    {

    case BLE_SRVC_EVT_STATE_NOTIFICATION_ENABLED:
        NRF_LOG_INFO("BLE_SRVC_EVT_STATE_NOTIFICATION_ENABLED");
        break;

    case BLE_SRVC_EVT_STATE_NOTIFICATION_DISABLED:
        NRF_LOG_INFO("BLE_SRVC_EVT_STATE_NOTIFICATION_DISABLED");
        break;

    case BLE_SRVC_EVT_CONNECTED:
        NRF_LOG_INFO("BLE_SRVC_OPT_EVT_CONNECTED");
        ble_gatts_value_t	t_value;
        t_value.p_value = &m_srm_state.evt_type;
	    t_value.len      = 1;
	    t_value.offset   = 0;
        err_code = sd_ble_gatts_value_set(p_cus_service->conn_handle, p_cus_service->state_char_handle.value_handle, &t_value);
    	APP_ERROR_CHECK(err_code);
        break;

    case BLE_SRVC_EVT_DISCONNECTED:
        NRF_LOG_INFO("BLE_SRVC_OPT_EVT_DISCONNECTED");
        break;

    case BLE_SRVC_EVT_STATE_CHAR_WRITE:
        //Should never happen as State is READ ONLY
        NRF_LOG_INFO("BLE_SRVC_EVT_STATE_CHAR_WRITE - Should not happen as READ ONLY");       
        break;
    
    case BLE_SRVC_EVT_CMD_CHAR_WRITE:
        NRF_LOG_INFO("BLE_SRVC_EVT_CMD_CHAR_WRITE");
        handle_cmd_chr(p_cus_service);       
        break;

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

/**@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 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;

    switch (p_evt->evt_id)
    {
    case PM_EVT_BONDED_PEER_CONNECTED:
    {
        NRF_LOG_INFO("Connected to a previously bonded device.");
    }
    break;

    case PM_EVT_CONN_SEC_SUCCEEDED:
    {
        NRF_LOG_INFO("Connection secured: role: %d, conn_handle: 0x%x, procedure: %d.",
                     ble_conn_state_role(p_evt->conn_handle),
                     p_evt->conn_handle,
                     p_evt->params.conn_sec_succeeded.procedure);
    }
    break;

    case PM_EVT_CONN_SEC_FAILED:
    {
        /* Often, when securing fails, it shouldn't be restarted, for security reasons.
             * Other times, it can be restarted directly.
             * Sometimes it can be restarted, but only after changing some Security Parameters.
             * Sometimes, it cannot be restarted until the link is disconnected and reconnected.
             * Sometimes it is impossible, to secure the link, or the peer device does not support it.
             * How to handle this error is highly application dependent. */
    }
    break;

    case PM_EVT_CONN_SEC_CONFIG_REQ:
    {
        // Reject pairing request from an already bonded peer.
        pm_conn_sec_config_t conn_sec_config = {.allow_repairing = false};
        pm_conn_sec_config_reply(p_evt->conn_handle, &conn_sec_config);
    }
    break;

    case PM_EVT_STORAGE_FULL:
    {
        // Run garbage collection on the flash.
        err_code = fds_gc();
        if (err_code == FDS_ERR_NO_SPACE_IN_QUEUES)
        {
            // Retry.
        }
        else
        {
            APP_ERROR_CHECK(err_code);
        }
    }
    break;

    case PM_EVT_PEERS_DELETE_SUCCEEDED:
    {
        advertising_start(false);
    }
    break;

    case PM_EVT_PEER_DATA_UPDATE_FAILED:
    {
        // Assert.
        APP_ERROR_CHECK(p_evt->params.peer_data_update_failed.error);
    }
    break;

    case PM_EVT_PEER_DELETE_FAILED:
    {
        // Assert.
        APP_ERROR_CHECK(p_evt->params.peer_delete_failed.error);
    }
    break;

    case PM_EVT_PEERS_DELETE_FAILED:
    {
        // Assert.
        APP_ERROR_CHECK(p_evt->params.peers_delete_failed_evt.error);
    }
    break;

    case PM_EVT_ERROR_UNEXPECTED:
    {
        // Assert.
        APP_ERROR_CHECK(p_evt->params.error_unexpected.error);
    }
    break;

    case PM_EVT_CONN_SEC_START:
    case PM_EVT_PEER_DATA_UPDATE_SUCCEEDED:
    case PM_EVT_PEER_DELETE_SUCCEEDED:
    case PM_EVT_LOCAL_DB_CACHE_APPLIED:
    case PM_EVT_LOCAL_DB_CACHE_APPLY_FAILED:
        // This can happen when the local DB has changed.
    case PM_EVT_SERVICE_CHANGED_IND_SENT:
    case PM_EVT_SERVICE_CHANGED_IND_CONFIRMED:
    default:
        break;
    }
}

/**@brief Function for handling the Battery measurement timer timeout.
 *
 * @details This function will be called each time the battery level measurement timer expires.
 *
 * @param[in] p_context  Pointer used for passing some arbitrary information (context) from the
 *                       app_start_timer() call to the timeout handler.
 */
static void services_state_timeout_handler(void *p_context)
{
    UNUSED_PARAMETER(p_context);
    ret_code_t err_code;

    // Increment the value of m_custom_value before nortifing it.
    err_code = ble_srvc_opt_custom_value_update(&m_srm_service, m_srm_state.evt_type);
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for the Timer initialization.
 *
 * @details Initializes the timer module. This creates and starts application timers.
 */
static void timers_init(void)
{
    // Initialize timer module.
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);

    // Create timers.

    /* YOUR_JOB: Create any timers to be used by the application.
                 Below is an example of how to create a timer.
                 For every new timer needed, increase the value of the macro APP_TIMER_MAX_TIMERS by
                 one.
       ret_code_t err_code;
       err_code = app_timer_create(&m_app_timer_id, APP_TIMER_MODE_REPEATED, timer_timeout_handler);
       APP_ERROR_CHECK(err_code); */

    err_code = app_timer_create(&m_service_notification_timer_id, APP_TIMER_MODE_REPEATED, services_state_timeout_handler);
    APP_ERROR_CHECK(err_code);

    //err_code = app_timer_create(&m_rawdata_get_notification_timer_id, APP_TIMER_MODE_REPEATED, rawdata_get_timeout_handler);
    //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);

    /* YOUR_JOB: Use an appearance value matching the application's use case.
       err_code = sd_ble_gap_appearance_set(BLE_APPEARANCE_);
       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);

    ble_gap_privacy_params_t prvt_conf;
    memset(&prvt_conf, 0, sizeof(prvt_conf));
    prvt_conf.privacy_mode = BLE_GAP_PRIVACY_MODE_DEVICE_PRIVACY;
    prvt_conf.private_addr_type = BLE_GAP_ADDR_TYPE_RANDOM_PRIVATE_RESOLVABLE ;
    prvt_conf.private_addr_cycle_s = 0;
    err_code = sd_ble_gap_privacy_set(&prvt_conf);
    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 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 initializing services that will be used by the application.
 */
static void services_init(void)
{
    ret_code_t err_code;
    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);

    /* YOUR_JOB: Add code to initialize the services used by the application.
       ble_xxs_init_t                     xxs_init;
       ble_yys_init_t                     yys_init;

       // Initialize XXX Service.
       memset(&xxs_init, 0, sizeof(xxs_init));

       xxs_init.evt_handler                = NULL;
       xxs_init.is_xxx_notify_supported    = true;
       xxs_init.ble_xx_initial_value.level = 100;

       err_code = ble_bas_init(&m_xxs, &xxs_init);
       APP_ERROR_CHECK(err_code);

       // Initialize YYY Service.
       memset(&yys_init, 0, sizeof(yys_init));
       yys_init.evt_handler                  = on_yys_evt;
       yys_init.ble_yy_initial_value.counter = 0;

       err_code = ble_yy_service_init(&yys_init, &yy_init);
       APP_ERROR_CHECK(err_code);
     */

    //Option Services
    ble_srvc_opt_init_t srvc_opt_init;
    // Initialize CUS Service init structure to zero.
    memset(&srvc_opt_init, 0, sizeof(srvc_opt_init));
    // Set the cus event handler
    srvc_opt_init.evt_handler = on_ble_srm_service_evt;
    err_code = ble_srvc_opt_init(&m_srm_service, &srvc_opt_init);
    APP_ERROR_CHECK(err_code);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&srvc_opt_init.custom_value_char_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&srvc_opt_init.custom_value_char_attr_md.write_perm);

}

/**@brief Function for handling 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)
{
    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 timers.
 */
static void application_timers_start(void)
{
    /* YOUR_JOB: Start your timers. below is an example of how to start a timer.
       ret_code_t err_code;
       err_code = app_timer_start(m_app_timer_id, TIMER_INTERVAL, NULL);
       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)
{
    ret_code_t err_code;

    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)
{
    ret_code_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)
{
    ret_code_t err_code = NRF_SUCCESS;

    switch (p_ble_evt->header.evt_id)
    {
    case BLE_GAP_EVT_DISCONNECTED:
        NRF_LOG_INFO("Disconnected.");
        // LED indication will be changed when advertising starts.
        break;

    case BLE_GAP_EVT_CONNECTED:
        NRF_LOG_INFO("Connected.");
        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);
        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.
        NRF_LOG_DEBUG("GATT - BLE_GATTC_EVT_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 - BLE_GATTS_EVT_TIMEOU.");
        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_GATTS_EVT_SYS_ATTR_MISSING:
        NRF_LOG_DEBUG("GATT -BLE_GATTS_EVT_SYS_ATTR_MISSING.");
        err_code = sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0, 0);
        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;

    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 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);
}

/**@brief Clear bond information from persistent storage.
 */
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 handling events from the BSP module.
 *
 * @param[in]   event   Event generated when button is pressed.
 */
static void bsp_event_handler(bsp_event_t event)
{
    ret_code_t err_code;

    switch (event)
    {
    case BSP_EVENT_SLEEP:
        sleep_mode_enter();
        break; // BSP_EVENT_SLEEP

    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; // BSP_EVENT_DISCONNECT

    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; // BSP_EVENT_KEY_0

    default:
        break;
    }
}

/**@brief Function for initializing the Advertising functionality.
 */
static void advertising_init(void)
{
    ret_code_t err_code;
    ble_advertising_init_t init;

    memset(&init, 0, sizeof(init));

    init.advdata.name_type = BLE_ADVDATA_SHORT_NAME;
    init.advdata.short_name_len = 3;
    init.advdata.include_appearance = true;
    init.advdata.flags = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;
    init.advdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
    init.advdata.uuids_complete.p_uuids = m_adv_uuids;
    //int8_t tx_power = -4;// Set Power Level
    //init.advdata.p_tx_power_level = &tx_power;

    ble_advdata_manuf_data_t                  manuf_data; //Variable to hold manufacturer specific data
    uint8_t data[]                            = MANUFACTURER_NAME; //Our data to advertise
    manuf_data.company_identifier             =  0x0059; //Nordics company ID
    manuf_data.data.p_data                    = data;
    manuf_data.data.size                      = sizeof(data);
    init.advdata.p_manuf_specific_data = &manuf_data;

    ble_advdata_manuf_data_t  manuf_data_response;
    uint8_t                     data_response[] = MANUFACTURER_NAME;
    manuf_data_response.company_identifier  = 0x0059;
    manuf_data_response.data.p_data         = data_response;
    manuf_data_response.data.size           = sizeof(data_response);
    init.srdata.name_type = BLE_ADVDATA_NO_NAME;
    init.srdata.p_manuf_specific_data = &manuf_data_response;

    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)
{
    ret_code_t err_code;
    bsp_event_t startup_event;

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

/**@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_DELETED_SUCEEDED event
    }
    else
    {
        ret_code_t err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);

        APP_ERROR_CHECK(err_code);
    }
}

void mpu_init(void)
{
    uint32_t err_code;
    // Initiate MPU driver
    err_code = app_mpu_init();
    APP_ERROR_CHECK(err_code); // Check for errors in return value
    
    // Setup and configure the MPU with intial values
    app_mpu_config_t p_mpu_config = MPU_DEFAULT_CONFIG(); // Load default values
    p_mpu_config.smplrt_div = 199;   // Change sampelrate. Sample Rate = Gyroscope Output Rate / (1 + SMPLRT_DIV). 199 gives a sample rate of 5Hz
    p_mpu_config.accel_config.afs_sel = AFS_2G; // Set accelerometer full scale range to 2G
    err_code = app_mpu_config(&p_mpu_config); // Configure the MPU with above values
    APP_ERROR_CHECK(err_code); // Check for errors in return value
    
    
    // This is a way to configure the interrupt pin behaviour
    app_mpu_int_pin_cfg_t p_int_pin_cfg = MPU_DEFAULT_INT_PIN_CONFIG(); // Default configurations
    p_int_pin_cfg.int_rd_clear = 1; // When this bit is equal to 1, interrupt status bits are cleared on any read operation
    err_code = app_mpu_int_cfg_pin(&p_int_pin_cfg); // Configure pin behaviour
    APP_ERROR_CHECK(err_code); // Check for errors in return value
    
    // Enable the MPU interrupts
    app_mpu_int_enable_t p_int_enable = MPU_DEFAULT_INT_ENABLE_CONFIG();
    p_int_enable.data_rdy_en = 1; // Trigger interrupt everytime new sensor values are available
    err_code = app_mpu_int_enable(&p_int_enable); // Configure interrupts
    APP_ERROR_CHECK(err_code); // Check for errors in return value    
}

/**
 * @brief Simple interrupt handler setting a flag indicating that data is ready
 *
 */
void int_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
    mpu_data_ready = true;
}

/**
 * @brief Function for initiating the GPIOTE module and enable the 
 * nRF5 to trigger an interrupt on a Low-To-High event on pin MPU_MPU_INT_PIN
 *
 */
static void gpiote_init(void)
{
    uint32_t err_code;
    if (!nrf_drv_gpiote_is_init())
    {
        err_code = nrf_drv_gpiote_init();
        APP_ERROR_CHECK(err_code);
    }
    
    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_LOTOHI(true);

    err_code = nrf_drv_gpiote_in_init(MPU_MPU_INT_PIN, &in_config, int_pin_handler);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_in_event_enable(MPU_MPU_INT_PIN, true);
}

/**@brief Function for the Power manager.
 */
static void power_manage(void)
{
    ret_code_t err_code = sd_app_evt_wait();
    APP_ERROR_CHECK(err_code);
}

/**@brief Function for application main entry.
 */
int main(void)
{

    //init State
    m_srm_state.evt_type = SR_IDLE;

    bool erase_bonds;

    // Initialize.
    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();

    gpiote_init();
    mpu_init();

    // Start execution.
    NRF_LOG_INFO("SRMotion started!!");
    application_timers_start();
    advertising_start(erase_bonds);

    uint32_t err_code;
    accel_values_t accel_values;

    // Enter main loop.
    for (;;)
    {
        if (NRF_LOG_PROCESS() == false)
        {
            power_manage();
            
            if ((mpu_data_ready == true) && (m_srm_state.evt_type == SR_RUN))
            {
                // Read accelerometer data.
                err_code = app_mpu_read_accel(&accel_values);
                APP_ERROR_CHECK(err_code);
                NRF_LOG_INFO("Accel: %05d, %05d, %05d, 0x%04X, 0x%04X, 0x%04X", accel_values.x, accel_values.y, accel_values.z, accel_values.x, accel_values.y, accel_values.z);
                mpu_data_ready = false;

                /**
                 * START - Test Send Function remove once working
                 **/
                if (&m_srm_service == NULL) {return NRF_ERROR_NULL;}	uint32_t err_code = NRF_SUCCESS;

	            //Setup the value to send
	            ble_gatts_value_t	t_value;
                uint8_t accvalues[6] = {accel_values.x, accel_values.y, accel_values.z, accel_values.x, accel_values.y, accel_values.z};
	            //uint8_t value[1] = {0xAA};
                t_value.p_value = accvalues;
	            t_value.len      = 1;
	            t_value.offset   = 0;

	            //setup the notification event
	            ble_gatts_hvx_params_t hvx_params;
                memset(&hvx_params, 0, sizeof(hvx_params));
                hvx_params.handle = m_srm_service.data_char_handle.value_handle;
	            hvx_params.type = BLE_GATT_HVX_NOTIFICATION;
                hvx_params.offset = t_value.offset;
	            hvx_params.p_len = &t_value.len;

	            //Set value
	            err_code = sd_ble_gatts_value_set(m_srm_service.conn_handle, m_srm_service.data_char_handle.value_handle, &t_value);
                APP_ERROR_CHECK(err_code);

	            //Set notification
                if ((m_srm_service.conn_handle != BLE_CONN_HANDLE_INVALID))
	            {
		            hvx_params.p_data = t_value.p_value;
		            err_code = sd_ble_gatts_hvx(m_srm_service.conn_handle, &hvx_params);
	            }
	            else
	            {
		            err_code = NRF_ERROR_INVALID_STATE;
	            }
                /**
                * END - Test Send Function remove once working
                **/

               mpu_data_ready = false;

            }
        }
    }


}

srm_service.h

0636.srm_service.h

srm_service.c

#include "sdk_common.h"
#include "ble_srv_common.h"
#include "srm_service.h"
#include <string.h>
#include "nrf_gpio.h"
#include "boards.h"
#include "nrf_log.h"
#include "app_mpu.h"

static const uint8_t state_char_name[] = "State";
static const uint8_t cmd_char_name[] = "Command";
static const uint8_t data_char_name[] = "Data";

/**@brief Function for initializing the Custom Service.
 *
 * @param[out]  p_cus       Custom Service structure. This structure will have to be supplied by
 *                          the application. It will be initialized by this function, and will later
 *                          be used to identify this particular service instance.
 * @param[in]   p_srvc_opt_init  Information needed to initialize the service.
 *
 * @return      NRF_SUCCESS on successful initialization of service, otherwise an error code.
 */

//Function for setting the State Characteristic
uint32_t ble_srvc_set_state(ble_srvc_opt_t *p_service, uint8_t state_value) {

	if (p_service == NULL) {return NRF_ERROR_NULL;}
	uint32_t err_code = NRF_SUCCESS;

	//Setup the value to send
	ble_gatts_value_t	t_value;
    t_value.p_value = &state_value;
	t_value.len      = 1;
	t_value.offset   = 0;

	//setup the notification event
	ble_gatts_hvx_params_t hvx_params;
    memset(&hvx_params, 0, sizeof(hvx_params));
    hvx_params.handle = p_service->state_char_handle.value_handle;
	hvx_params.type = BLE_GATT_HVX_NOTIFICATION;
    hvx_params.offset = t_value.offset;
	hvx_params.p_len = &t_value.len;

	//Set value
	err_code = sd_ble_gatts_value_set(p_service->conn_handle, p_service->state_char_handle.value_handle, &t_value);
    APP_ERROR_CHECK(err_code);

	//Set notification
    if ((p_service->conn_handle != BLE_CONN_HANDLE_INVALID))
	{
		hvx_params.p_data = t_value.p_value;
		err_code = sd_ble_gatts_hvx(p_service->conn_handle, &hvx_params);
	}
	else
	{
		err_code = NRF_ERROR_INVALID_STATE;
	}

	return err_code;
}

uint32_t ble_srvc_opt_custom_value_update(ble_srvc_opt_t *p_cus, uint8_t custom_value)
{
	NRF_LOG_INFO("In ble_srvc_opt_custom_value_update. \r\n");
	if (p_cus == NULL)
	{
		return NRF_ERROR_NULL;
	}

	uint32_t err_code = NRF_SUCCESS;
	ble_gatts_value_t gatts_value;

	// Initialize value struct.
	memset(&gatts_value, 0, sizeof(gatts_value));

	gatts_value.len = sizeof(uint8_t);
	gatts_value.offset = 0;
	gatts_value.p_value = &custom_value;

	// Update database.
	err_code = sd_ble_gatts_value_set(p_cus->conn_handle,
									  p_cus->state_char_handle.value_handle,
									  &gatts_value);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	// Send value if connected and notifying.
	if ((p_cus->conn_handle != BLE_CONN_HANDLE_INVALID))
	{
		ble_gatts_hvx_params_t hvx_params;

		memset(&hvx_params, 0, sizeof(hvx_params));

		hvx_params.handle = p_cus->state_char_handle.value_handle;
		hvx_params.type = BLE_GATT_HVX_NOTIFICATION;
		hvx_params.offset = gatts_value.offset;
		hvx_params.p_len = &gatts_value.len;
		hvx_params.p_data = gatts_value.p_value;

		err_code = sd_ble_gatts_hvx(p_cus->conn_handle, &hvx_params);
	}
	else
	{
		err_code = NRF_ERROR_INVALID_STATE;
	}

	return err_code;
}

//Adding the State Characteristic
static uint32_t state_char_add(ble_srvc_opt_t *p_cus, const ble_srvc_opt_init_t *p_srvc_opt_init, uint16_t uuid)
{
	uint32_t err_code;
	ble_gatts_char_md_t char_md;
	ble_gatts_attr_md_t cccd_md;
	ble_gatts_attr_t attr_char_value;
	ble_uuid_t ble_uuid;
	ble_gatts_attr_md_t attr_md;

	memset(&char_md, 0, sizeof(char_md));

	char_md.char_props.read = 1;
	char_md.char_props.write = 0;
	char_md.char_props.notify = 1;
	char_md.p_char_user_desc = state_char_name;
	char_md.char_user_desc_size = sizeof(state_char_name);
	char_md.char_user_desc_max_size = sizeof(state_char_name);
	char_md.p_char_pf = NULL;
	char_md.p_user_desc_md = NULL;
	char_md.p_cccd_md = NULL;
	char_md.p_sccd_md = NULL;

	memset(&attr_md, 0, sizeof(attr_md));

	attr_md.read_perm = p_srvc_opt_init->custom_value_char_attr_md.read_perm;
	attr_md.write_perm = p_srvc_opt_init->custom_value_char_attr_md.write_perm;
	attr_md.vloc = BLE_GATTS_VLOC_STACK;
	attr_md.rd_auth = 0;
	attr_md.wr_auth = 0;
	attr_md.vlen = 0;

	ble_uuid.type = p_cus->uuid_type;
	ble_uuid.uuid = BLE_SRM_STATE_CHAR_UUID;
	//ble_uuid.uuid = uuid;

	memset(&attr_char_value, 0, sizeof(attr_char_value));

	attr_char_value.p_uuid = &ble_uuid;
	attr_char_value.p_attr_md = &attr_md;
	attr_char_value.init_len = sizeof(uint8_t);
	attr_char_value.init_offs = 0;
	attr_char_value.max_len = sizeof(uint8_t);
	uint8_t value[1] = {0x00};
	attr_char_value.p_value = value;

	memset(&cccd_md, 0, sizeof(cccd_md));

	//  Read  operation on Cccd should be possible without authentication.
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);

	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);

	cccd_md.vloc = BLE_GATTS_VLOC_STACK;

	char_md.p_cccd_md = &cccd_md;

	err_code = sd_ble_gatts_characteristic_add(p_cus->service_handle, &char_md,
											   &attr_char_value,
											   &p_cus->state_char_handle);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	return NRF_SUCCESS;
}

//Adding the Command Characteristic
static uint32_t cmd_char_add(ble_srvc_opt_t *p_cus, const ble_srvc_opt_init_t *p_srvc_opt_init, uint16_t uuid)
{
	uint32_t err_code;
	ble_gatts_char_md_t char_md;
	ble_gatts_attr_md_t cccd_md;
	ble_gatts_attr_t attr_char_value;
	ble_uuid_t ble_uuid;
	ble_gatts_attr_md_t attr_md;

	memset(&char_md, 0, sizeof(char_md));

	char_md.char_props.read = 1;
	char_md.char_props.write = 1;
	char_md.char_props.notify = 0;
	char_md.p_char_user_desc = cmd_char_name;
	char_md.char_user_desc_size = sizeof(cmd_char_name);
	char_md.char_user_desc_max_size = sizeof(cmd_char_name);
	char_md.p_char_pf = NULL;
	char_md.p_user_desc_md = NULL;
	char_md.p_cccd_md = NULL;
	char_md.p_sccd_md = NULL;

	memset(&attr_md, 0, sizeof(attr_md));

	attr_md.read_perm = p_srvc_opt_init->custom_value_char_attr_md.read_perm;
	attr_md.write_perm = p_srvc_opt_init->custom_value_char_attr_md.write_perm;
	attr_md.vloc = BLE_GATTS_VLOC_STACK;
	attr_md.rd_auth = 0;
	attr_md.wr_auth = 0;
	attr_md.vlen = 0;

	ble_uuid.type = p_cus->uuid_type;
	ble_uuid.uuid = BLE_SRM_CMD_CHAR_UUID;

	memset(&attr_char_value, 0, sizeof(attr_char_value));

	attr_char_value.p_uuid = &ble_uuid;
	attr_char_value.p_attr_md = &attr_md;
	attr_char_value.init_len = sizeof(uint8_t);
	attr_char_value.init_offs = 0;
	attr_char_value.max_len = sizeof(uint8_t);
	uint8_t value[1] = {0x00};
	attr_char_value.p_value = value;

	memset(&cccd_md, 0, sizeof(cccd_md));

	//  Read  operation on Cccd should be possible without authentication.
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);

	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);

	cccd_md.vloc = BLE_GATTS_VLOC_STACK;

	char_md.p_cccd_md = &cccd_md;

	err_code = sd_ble_gatts_characteristic_add(p_cus->service_handle, &char_md,
											   &attr_char_value,
											   &p_cus->cmd_char_handle);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	return NRF_SUCCESS;
}

//Adding the Data Characteristic
static uint32_t data_char_add(ble_srvc_opt_t *p_cus, const ble_srvc_opt_init_t *p_srvc_opt_init, uint16_t uuid)
{
	uint32_t err_code;
	ble_gatts_char_md_t char_md;
	ble_gatts_attr_md_t cccd_md;
	ble_gatts_attr_t attr_char_value;
	ble_uuid_t ble_uuid;
	ble_gatts_attr_md_t attr_md;

	memset(&char_md, 0, sizeof(char_md));

	char_md.char_props.read = 1;
	char_md.char_props.write = 0;
	char_md.char_props.notify = 1;
	char_md.p_char_user_desc = data_char_name;
	char_md.char_user_desc_size = sizeof(data_char_name);
	char_md.char_user_desc_max_size = sizeof(data_char_name);
	char_md.p_char_pf = NULL;
	char_md.p_user_desc_md = NULL;
	char_md.p_cccd_md = NULL;
	char_md.p_sccd_md = NULL;

	memset(&attr_md, 0, sizeof(attr_md));

	attr_md.read_perm = p_srvc_opt_init->custom_value_char_attr_md.read_perm;
	attr_md.write_perm = p_srvc_opt_init->custom_value_char_attr_md.write_perm;
	attr_md.vloc = BLE_GATTS_VLOC_STACK;
	attr_md.rd_auth = 0;
	attr_md.wr_auth = 0;
	attr_md.vlen = 0;

	ble_uuid.type = p_cus->uuid_type;
	ble_uuid.uuid = BLE_SRM_CMD_CHAR_UUID;

	memset(&attr_char_value, 0, sizeof(attr_char_value));

	attr_char_value.p_uuid = &ble_uuid;
	attr_char_value.p_attr_md = &attr_md;
	attr_char_value.init_len = sizeof(data_values_t);
	//attr_char_value.init_offs = 0;
	attr_char_value.max_len = sizeof(data_values_t);
	uint8_t value[8] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08};
	attr_char_value.p_value = value;

	memset(&cccd_md, 0, sizeof(cccd_md));

	//  Read  operation on Cccd should be possible without authentication.
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);

	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
	BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);

	cccd_md.vloc = BLE_GATTS_VLOC_STACK;

	char_md.p_cccd_md = &cccd_md;

	err_code = sd_ble_gatts_characteristic_add(p_cus->service_handle, &char_md,
											   &attr_char_value,
											   &p_cus->data_char_handle);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	return NRF_SUCCESS;
}

//Initialise the Service and add the Characteristics
uint32_t ble_srvc_opt_init(ble_srvc_opt_t *p_cus, const ble_srvc_opt_init_t *p_srvc_opt_init)
{

	if (p_cus == NULL || p_srvc_opt_init == NULL)
	{
		return NRF_ERROR_NULL;
	}

	uint32_t err_code;
	ble_uuid_t ble_uuid;
	uint16_t cus_char_uuid;

	// Initialize service structure
	p_cus->evt_handler = p_srvc_opt_init->evt_handler;
	p_cus->conn_handle = BLE_CONN_HANDLE_INVALID;

	// Add Custom Service UUID
	ble_uuid128_t base_uuid = {BLE_SRM_SERVICE_BASE_UUID};
	err_code = sd_ble_uuid_vs_add(&base_uuid, &p_cus->uuid_type);
	VERIFY_SUCCESS(err_code);

	ble_uuid.type = p_cus->uuid_type;
	ble_uuid.uuid = BLE_SRM_SERVICE_UUID;

	// Add the Custom Service
	err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY, &ble_uuid, &p_cus->service_handle);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	// Add the State Characteristic
	err_code = state_char_add(p_cus, p_srvc_opt_init, cus_char_uuid);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

    // Add the Command Characteristic
	err_code = cmd_char_add(p_cus, p_srvc_opt_init, cus_char_uuid);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

    // Add the Data Characteristic
	err_code = data_char_add(p_cus, p_srvc_opt_init, cus_char_uuid);
	if (err_code != NRF_SUCCESS)
	{
		return err_code;
	}

	return err_code;
}

/**@brief Function for handling the Connect event.
 *
 * @param[in]   p_cus       Custom Service structure.
 * @param[in]   p_ble_evt   Event received from the BLE stack.
 */
static void on_connect(ble_srvc_opt_t *p_cus, ble_evt_t const *p_ble_evt)
{
	p_cus->conn_handle = p_ble_evt->evt.gap_evt.conn_handle;

	ble_srvc_opt_evt_t evt;

	evt.evt_type = BLE_SRVC_EVT_CONNECTED;

	p_cus->evt_handler(p_cus, &evt);

}

/**@brief Function for handling the Disconnect event.
 *
 * @param[in]   p_cus       Custom Service structure.
 * @param[in]   p_ble_evt   Event received from the BLE stack.
 */
static void on_disconnect(ble_srvc_opt_t *p_cus, ble_evt_t const *p_ble_evt)
{
	UNUSED_PARAMETER(p_ble_evt);
	p_cus->conn_handle = BLE_CONN_HANDLE_INVALID;
	//nrf_gpio_pin_toggle(LED_4);
}

static void on_write(ble_srvc_opt_t *p_cus, ble_evt_t const *p_ble_evt)
{
	//ble_gatts_evt_write_t * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;
	ble_gatts_evt_write_t const *p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;

	// State Characteristic Written to.
	if (p_evt_write->handle == p_cus->state_char_handle.value_handle)
	{
		if (p_cus->evt_handler != NULL)
		{
			//Set and Call the application event handler
			ble_srvc_opt_evt_t evt;
			evt.evt_type = BLE_SRVC_EVT_STATE_CHAR_WRITE;
			p_cus->evt_handler(p_cus, &evt);

		}
	}

    // Command Characteristic Written to.
	if (p_evt_write->handle == p_cus->cmd_char_handle.value_handle)
	{
		if (p_cus->evt_handler != NULL)
		{
			//Set and Call the application event handler
			ble_srvc_opt_evt_t evt;
			evt.evt_type = BLE_SRVC_EVT_CMD_CHAR_WRITE;
			p_cus->evt_handler(p_cus, &evt);

		}
	}

	// Check if the Custom value CCCD is written to and that the value is the appropriate length, i.e 2 bytes.
	if ((p_evt_write->handle == p_cus->state_char_handle.cccd_handle) && (p_evt_write->len == 2))
	{
		// CCCD written, call application event handler
		if (p_cus->evt_handler != NULL)
		{
			ble_srvc_opt_evt_t evt;

			if (ble_srv_is_notification_enabled(p_evt_write->data))
			{
				evt.evt_type = BLE_SRVC_EVT_STATE_NOTIFICATION_ENABLED;
				//NRF_LOG_INFO("ble_srvc_opt- on_write - BLE_SRVC_OPT_EVT_NOTIFICATION_ENABLED");
			}
			else
			{
				evt.evt_type = BLE_SRVC_EVT_STATE_NOTIFICATION_DISABLED;
				//NRF_LOG_INFO("ble_srvc_opt - on_write - BLE_SRVC_OPT_EVT_NOTIFICATION_DISABLED");
			}
			// Call the application event handler.
			p_cus->evt_handler(p_cus, &evt);
		}
	}
}

void ble_srvc_opt_on_ble_evt(ble_evt_t const *p_ble_evt, void *p_context)
{
	ble_srvc_opt_t *p_cus = (ble_srvc_opt_t *)p_context;

	if (p_cus == NULL || p_ble_evt == NULL)
	{
		return;
	}

	switch (p_ble_evt->header.evt_id)
	{
	case BLE_GAP_EVT_CONNECTED:
		NRF_LOG_INFO("ble_srvc_opt - BLE_GAP_EVT_CONNECTED");
		on_connect(p_cus, p_ble_evt);
		break;

	case BLE_GAP_EVT_DISCONNECTED:
		NRF_LOG_INFO("ble_srvc_opt - BLE_GAP_EVT_DISCONNECTED");
		on_disconnect(p_cus, p_ble_evt);
		break;
	case BLE_GATTS_EVT_WRITE:
		on_write(p_cus, p_ble_evt);
		break;
	default:
		// No implementation needed.
		break;
	}
}

uint32_t ble_mpu_update(ble_srvc_opt_t *p_cus, accel_values_t * accel_values)
{
    // Send value if connected and notifying
    if (p_cus->conn_handle == BLE_CONN_HANDLE_INVALID)
    {
        return NRF_ERROR_INVALID_STATE;
    }
    
    uint16_t               len = sizeof(accel_values_t);
    ble_gatts_hvx_params_t hvx_params;
    memset(&hvx_params, 0, sizeof(hvx_params));

	hvx_params.handle = p_cus->data_char_handle.value_handle;
    hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;
    hvx_params.offset = 0;
    hvx_params.p_len  = &len;
    hvx_params.p_data = (uint8_t*)accel_values;  

    return sd_ble_gatts_hvx(p_cus->conn_handle, &hvx_params);
}

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