text: /* Copyright (c) 2014 Nordic Semiconductor. All Rights Reserved.
   *
   * The information contained herein is property of Nordic Semiconductor ASA.
   * Terms and conditions of usage are described in detail in NORDIC
   * SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
   *
   * Licensees are granted free, non-transferable use of the information. NO
   * WARRANTY of ANY KIND is provided. This heading must NOT be removed from
   * the file.
   *
   */
  
  /** @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.
   */
  
  #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 "softdevice_handler.h"
  #include "app_timer.h"
  #include "app_button.h"
  #include "ble_nus.h"
  #include "app_uart.h"
  #include "app_util_platform.h"
  #include "bsp.h"
  #include "bsp_btn_ble.h"
  #include "nrf_drv_adc.h"
  #include "nrf_delay.h"
  
  #define IS_SRVC_CHANGED_CHARACT_PRESENT 0                                           /**< Include the service_changed characteristic. If not enabled, the server's database cannot be changed for the lifetime of the device. */
  
  #if (NRF_SD_BLE_API_VERSION == 3)
  #define NRF_BLE_MAX_MTU_SIZE            GATT_MTU_SIZE_DEFAULT                       /**< MTU size used in the softdevice enabling and to reply to a BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST event. */
  #endif
  
  #define APP_FEATURE_NOT_SUPPORTED       BLE_GATT_STATUS_ATTERR_APP_BEGIN + 2        /**< Reply when unsupported features are requested. */
  
  #define CENTRAL_LINK_COUNT              0                                           /**< Number of central links used by the application. When changing this number remember to adjust the RAM settings*/
  #define PERIPHERAL_LINK_COUNT           1                                           /**< Number of peripheral links used by the application. When changing this number remember to adjust the RAM settings*/
  
  #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_ADV_INTERVAL                64                                          /**< The advertising interval (in units of 0.625 ms. This value corresponds to 40 ms). */
  #define APP_ADV_TIMEOUT_IN_SECONDS      180                                         /**< The advertising timeout (in units of seconds). */
  
  #define APP_TIMER_PRESCALER             0                                           /**< Value of the RTC1 PRESCALER register. */
  #define APP_TIMER_OP_QUEUE_SIZE         4                                           /**< Size of timer operation queues. */
  
  #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, APP_TIMER_PRESCALER)  /**< 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, APP_TIMER_PRESCALER) /**< 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 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. */
  
  #define ADC_BUFFER_SIZE 4                                                           /**< Size of buffer for ADC samples.  */
  static nrf_adc_value_t                  adc_buffer[ADC_BUFFER_SIZE];                /**< ADC buffer. */
  static nrf_drv_adc_channel_t            m_channel_config = NRF_DRV_ADC_DEFAULT_CHANNEL(NRF_ADC_CONFIG_INPUT_2); /**< Channel instance. Default configuration used. */
  static uint8_t                          adc_event_counter = 0;
  
  
  static ble_nus_t                        m_nus;                                      /**< Structure to identify the Nordic UART Service. */
  static uint16_t                         m_conn_handle = BLE_CONN_HANDLE_INVALID;    /**< Handle of the current connection. */
  
  static ble_uuid_t                       m_adv_uuids[] = {{BLE_UUID_NUS_SERVICE, NUS_SERVICE_UUID_TYPE}};  /**< Universally unique service identifier. */
  
  
  /**@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 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);
  
      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 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_nus    Nordic UART Service structure.
   * @param[in] p_data   Data to be send to UART module.
   * @param[in] length   Length of the data.
   */
  /**@snippet [Handling the data received over BLE] */
  static void nus_data_handler(ble_nus_t * p_nus, uint8_t * p_data, uint16_t length)
  {
      for (uint32_t i = 0; i < length; i++)
      {
          while (app_uart_put(p_data[i]) != NRF_SUCCESS);
      }
      while (app_uart_put('\r') != NRF_SUCCESS);
      while (app_uart_put('\n') != NRF_SUCCESS);
  }
  /**@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;
  
      memset(&nus_init, 0, sizeof(nus_init));
  
      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:
              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 the application's SoftDevice event handler.
   *
   * @param[in] p_ble_evt SoftDevice event.
   */
  static void on_ble_evt(ble_evt_t * p_ble_evt)
  {
      uint32_t err_code;
  
      switch (p_ble_evt->header.evt_id)
      {
          case BLE_GAP_EVT_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;
              break; // BLE_GAP_EVT_CONNECTED
  
          case BLE_GAP_EVT_DISCONNECTED:
              err_code = bsp_indication_set(BSP_INDICATE_IDLE);
              APP_ERROR_CHECK(err_code);
              m_conn_handle = BLE_CONN_HANDLE_INVALID;
              break; // BLE_GAP_EVT_DISCONNECTED
  
          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; // BLE_GAP_EVT_SEC_PARAMS_REQUEST
  
          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; // BLE_GATTS_EVT_SYS_ATTR_MISSING
  
          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; // BLE_GATTC_EVT_TIMEOUT
  
          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; // BLE_GATTS_EVT_TIMEOUT
  
          case BLE_EVT_USER_MEM_REQUEST:
              err_code = sd_ble_user_mem_reply(p_ble_evt->evt.gattc_evt.conn_handle, NULL);
              APP_ERROR_CHECK(err_code);
              break; // BLE_EVT_USER_MEM_REQUEST
  
          case BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST:
          {
              ble_gatts_evt_rw_authorize_request_t  req;
              ble_gatts_rw_authorize_reply_params_t auth_reply;
  
              req = p_ble_evt->evt.gatts_evt.params.authorize_request;
  
              if (req.type != BLE_GATTS_AUTHORIZE_TYPE_INVALID)
              {
                  if ((req.request.write.op == BLE_GATTS_OP_PREP_WRITE_REQ)     ||
                      (req.request.write.op == BLE_GATTS_OP_EXEC_WRITE_REQ_NOW) ||
                      (req.request.write.op == BLE_GATTS_OP_EXEC_WRITE_REQ_CANCEL))
                  {
                      if (req.type == BLE_GATTS_AUTHORIZE_TYPE_WRITE)
                      {
                          auth_reply.type = BLE_GATTS_AUTHORIZE_TYPE_WRITE;
                      }
                      else
                      {
                          auth_reply.type = BLE_GATTS_AUTHORIZE_TYPE_READ;
                      }
                      auth_reply.params.write.gatt_status = APP_FEATURE_NOT_SUPPORTED;
                      err_code = sd_ble_gatts_rw_authorize_reply(p_ble_evt->evt.gatts_evt.conn_handle,
                                                                 &auth_reply);
                      APP_ERROR_CHECK(err_code);
                  }
              }
          } break; // BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST
  
  #if (NRF_SD_BLE_API_VERSION == 3)
          case BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST:
              err_code = sd_ble_gatts_exchange_mtu_reply(p_ble_evt->evt.gatts_evt.conn_handle,
                                                         NRF_BLE_MAX_MTU_SIZE);
              APP_ERROR_CHECK(err_code);
              break; // BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST
  #endif
  
          default:
              // No implementation needed.
              break;
      }
  }
  
  
  /**@brief Function for dispatching a SoftDevice event to all modules with a SoftDevice
   *        event handler.
   *
   * @details This function is called from the SoftDevice event interrupt handler after a
   *          SoftDevice event has been received.
   *
   * @param[in] p_ble_evt  SoftDevice event.
   */
  static void ble_evt_dispatch(ble_evt_t * p_ble_evt)
  {
      ble_conn_params_on_ble_evt(p_ble_evt);
      ble_nus_on_ble_evt(&m_nus, p_ble_evt);
      on_ble_evt(p_ble_evt);
      ble_advertising_on_ble_evt(p_ble_evt);
      bsp_btn_ble_on_ble_evt(p_ble_evt);
  
  }
  
  
  /**@brief Function for the SoftDevice initialization.
   *
   * @details This function initializes the SoftDevice and the BLE event interrupt.
   */
  static void ble_stack_init(void)
  {
      uint32_t err_code;
  
      nrf_clock_lf_cfg_t clock_lf_cfg = NRF_CLOCK_LFCLKSRC;
  
      // Initialize SoftDevice.
      SOFTDEVICE_HANDLER_INIT(&clock_lf_cfg, NULL);
  
      ble_enable_params_t ble_enable_params;
      err_code = softdevice_enable_get_default_config(CENTRAL_LINK_COUNT,
                                                      PERIPHERAL_LINK_COUNT,
                                                      &ble_enable_params);
      APP_ERROR_CHECK(err_code);
  
      //Check the ram settings against the used number of links
      CHECK_RAM_START_ADDR(CENTRAL_LINK_COUNT,PERIPHERAL_LINK_COUNT);
  
      // Enable BLE stack.
  #if (NRF_SD_BLE_API_VERSION == 3)
      ble_enable_params.gatt_enable_params.att_mtu = NRF_BLE_MAX_MTU_SIZE;
  #endif
      err_code = softdevice_enable(&ble_enable_params);
      APP_ERROR_CHECK(err_code);
  
      // Subscribe for BLE events.
      err_code = softdevice_ble_evt_handler_set(ble_evt_dispatch);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@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();
                  if (err_code != NRF_ERROR_INVALID_STATE)
                  {
                      APP_ERROR_CHECK(err_code);
                  }
              }
              break;
  
          case BSP_EVENT_KEY_0:
   				LEDS_ON(BSP_LED_1_MASK);
              break;
          
          case BSP_EVENT_KEY_1:
                  LEDS_OFF(BSP_LED_1_MASK);
              break;
          
          default:
              break;
      }
  }
  
  
  /**@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' i.e '\r\n' (hex 0x0D) or if the string has reached a length of
   *          @ref NUS_MAX_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') || (index >= (BLE_NUS_MAX_DATA_LEN)))
              {
                  err_code = ble_nus_string_send(&m_nus, data_array, index);
                  if (err_code != NRF_ERROR_INVALID_STATE)
                  {
                      APP_ERROR_CHECK(err_code);
                  }
  
                  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;
      const app_uart_comm_params_t comm_params =
      {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          APP_UART_FLOW_CONTROL_DISABLED,
          false,
          UART_BAUDRATE_BAUDRATE_Baud115200
      };
  
      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 initializing the Advertising functionality.
   */
  static void advertising_init(void)
  {
      uint32_t               err_code;
      ble_advdata_t          advdata;
      ble_advdata_t          scanrsp;
      ble_adv_modes_config_t options;
  
      // Build advertising data struct to pass into @ref ble_advertising_init.
      memset(&advdata, 0, sizeof(advdata));
      advdata.name_type          = BLE_ADVDATA_FULL_NAME;
      advdata.include_appearance = false;
      advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_LIMITED_DISC_MODE;
  
      memset(&scanrsp, 0, sizeof(scanrsp));
      scanrsp.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
      scanrsp.uuids_complete.p_uuids  = m_adv_uuids;
  
      memset(&options, 0, sizeof(options));
      options.ble_adv_fast_enabled  = true;
      options.ble_adv_fast_interval = APP_ADV_INTERVAL;
      options.ble_adv_fast_timeout  = APP_ADV_TIMEOUT_IN_SECONDS;
  
      err_code = ble_advertising_init(&advdata, &scanrsp, &options, on_adv_evt, NULL);
      APP_ERROR_CHECK(err_code);
  }
  
  
  /**@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_LED | BSP_INIT_BUTTONS,
                                   APP_TIMER_TICKS(100, APP_TIMER_PRESCALER),
                                   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 placing the application in low power state while waiting for events.
   */
  static void power_manage(void)
  {
      uint32_t err_code = sd_app_evt_wait();
      APP_ERROR_CHECK(err_code);
  }
  
  /**
   * @brief ADC interrupt handler.
   * Prints ADC results on hardware UART and over BLE via the NUS service.
   */
  static void adc_event_handler(nrf_drv_adc_evt_t const * p_event)
  {
      uint8_t adc_result[ADC_BUFFER_SIZE*2];
  	
      if (p_event->type == NRF_DRV_ADC_EVT_DONE)
      {
          adc_event_counter++;
          printf("    ADC event counter: %d\r\n", adc_event_counter);			
          uint32_t i;
          for (i = 0; i < p_event->data.done.size; i++)
          {
              printf("Sample value %d: %d\r\n", (unsigned int)i+1, p_event->data.done.p_buffer[i]);   //Print ADC result on hardware UART
              adc_result[(i*2)] = p_event->data.done.p_buffer[i] >> 8;
              adc_result[(i*2)+1] = p_event->data.done.p_buffer[i];					
          }
          if(ADC_BUFFER_SIZE <= 10)
          {
              ble_nus_string_send(&m_nus, &adc_result[0], ADC_BUFFER_SIZE*2);           //Send ADC result over BLE via NUS service
          }		
          LEDS_INVERT(BSP_LED_3_MASK);				                                          //Indicate sampling complete on LED 4
      }
  }
  
  /**
   * @brief ADC initialization.
   */
  static void adc_config(void)
  {
      ret_code_t ret_code;
      nrf_drv_adc_config_t config = NRF_DRV_ADC_DEFAULT_CONFIG;
  
      ret_code = nrf_drv_adc_init(&config, adc_event_handler);
      APP_ERROR_CHECK(ret_code);
  
      nrf_drv_adc_channel_enable(&m_channel_config);
  }
  
  /**@brief Application main function.
   */
  int main(void)
  {
      uint32_t err_code;
      bool erase_bonds;
  
      // Initialize.
      APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
      uart_init();
  
      buttons_leds_init(&erase_bonds);
      ble_stack_init();
      gap_params_init();
      services_init();
      advertising_init();
      conn_params_init();
  
      printf("\r\nUART Start!\r\n");
      err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
      APP_ERROR_CHECK(err_code);
      
      adc_config();
  
      // Enter main loop.
      for (;;)
      {
          APP_ERROR_CHECK(nrf_drv_adc_buffer_convert(adc_buffer,ADC_BUFFER_SIZE));   //Allocate buffer for ADC
          for (uint32_t i = 0; i < ADC_BUFFER_SIZE; i++)
          {
              nrf_drv_adc_sample();           // manually trigger ADC conversion
              power_manage();                 // CPU enter sleep mode during sampling. CPU will be enabled again when ADC interrupt occurs and adc_event_handler is called
              LEDS_INVERT(BSP_LED_1_MASK);    // Indicate sampling complete
              nrf_delay_ms(250);              // Slow down sampling frequency with 250ms blocking delay
          }
      }
  }
  
  
  /**
   * @}
   */
  