Sending PDF files through BLE_APP_UART

[Mani]

Hi,

I am using ble_app_uart service in my application. I am trying to send files using teraterm tool. If I am sending .txt or .doc files there is no disconnection in the devices. But if I am sending PDF or PPT file there is a disconnection between central and peripheral device. Is there any issue in sending PDF files? Also I am seeing some data loss while sending .txt or  .doc files.

Need a urgent solution for this.

[haakonsh]

Hey Manigandan,

I need some detail on your implementation and more importantly some debugging information(source code, logs, error info, sniffer logs, etc). 

I think the two symptoms, disconnections and data corruptions, might be unrelated. 

The BLE_APP_UART example is sends ASCII strings over BLE and it is completely agnostic to it's string content with one exception. From Handling data received over UART: 

"The implementation of the example requires the newline character to be '\n'. Some terminals use different characters to trigger a newline, for example '\r'. Therefore, you might need to configure your terminal to interpret only '\n' as a newline."

The reason why the doc and txt files have less corruption might be because they use less special characters or '\r' as newlines, or something in that direction. 

Cheers,

Håkon.

[Mani]

Find the code in the attached file

.

Fullscreen 44716.main.c Download

/* 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 <stdbool.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 "nrf_uarte.h"

#include "app_util_platform.h"
#include "bsp.h"
#include "app_fifo.h"
#include "bsp_btn_ble.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"

#define EVENT_SIZE 20
#define QUEUE_SIZE 5

#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. */

#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                     "BLE_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      0                                        /**< 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               7.5 //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               7.5 //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(7500, 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 MAX_PKT_SIZE                    20
#define MAX_SIZE                        1024                                        /** < Maximum no.of bytes in 2kB Memory. */

static uint32_t baud_rate=UART_BAUDRATE_BAUDRATE_Baud115200;
static void uart_init(void);
typedef struct _my_queue
   {
       int         head;
       int         tail;
       int         count;
       unsigned char  buffer[MAX_SIZE];
   } MY_QUEUE;

/* Queue implementation */

                                 
#define StructQueuePeekTail(q,N) ( ((q)->tail < (N-1))         ?  \
                                     &(q)->buffer[(q)->tail+1] :  \
                                     &(q)->buffer[0]              )


#define StructQueueIsFull(q,N) ( (q)->count >= N )

#define StructQueueIsNotFull(q,N) ( (q)->count < N )

#define StructQueueIsEmpty(q,N) ( (q)->count == 0 )

#define StructQueueIsNotEmpty(q,N) ( (q)->count != 0 )

#define StructQueueCount(q,N) ( (q)->count )
#define StructQueueSpaceAvailable(c,q,N) ( ((q)->count + c) <= N )


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. */
void start_timer(void);
static uint8_t data_array[32];
MY_QUEUE UartQueue;


uint8_t received_pkts=0,intr_count=1,buff_over_wrt=0;
static uint16_t bytereceivedCount ;

void StructQueueInit(MY_QUEUE * q) 
{
   (q)->head  = 0;                              //(  (q)->head  = (N), \
   (q)->tail  = 0;                              //(q)->tail  = (N), \
   (q)->count = 0;                              //(q)->count =  0   )
}
void StructQueueAdd(MY_QUEUE * q, uint8_t inByte) 
{ 
  (q)->count++;            
  if((q)->head < (MAX_SIZE-1))            //( ((q)->head < (MAX_SIZE-1)) ?  
    (q)->head++  ;                        //((q)->head++)     :  
  else
    ((q)->head=0);                        //((q)->head=0)     ), 
  
   if((q)->head == (q)->tail)
      printf("\r\nBuffer overrun !!\r\n");
   
  (q)->buffer[(q)->head]  = inByte;       //&(q)->buffer[(q)->head] 
   bytereceivedCount++;
   
}


int flag=0,                     /* */
    flag1=0;                    /* */

void StructQueueRemove(MY_QUEUE * q, uint8_t * inByte) 
{
  (q)->count--;                                   
                          
   *inByte = (q)->buffer[(q)->tail] ;       
    if ((q)->tail < (MAX_SIZE-1))              
     ((q)->tail++) ;                      
  else
     (q)->tail=0; 
}

void start_timer(void)
{		
  NRF_TIMER2->MODE = TIMER_MODE_MODE_Counter;              // Set the timer in Counter Mode
  NRF_TIMER2->TASKS_CLEAR = 1;                             // clear the task first to be usable for later
	NRF_TIMER2->BITMODE = TIMER_BITMODE_BITMODE_16Bit;		   //Set counter to 16 bit resolution
	NRF_TIMER2->CC[0] = 7;                                   //Set value for TIMER2 compare register 0
	NRF_TIMER2->CC[1] = 0;                                   //Set value for TIMER2 compare register 1
		
  // Enable interrupt on Timer 2, both for CC[0] and CC[1] compare match events
	
	NRF_TIMER2->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos) | (TIMER_INTENSET_COMPARE1_Enabled << TIMER_INTENSET_COMPARE1_Pos);
  NVIC_EnableIRQ(TIMER2_IRQn);
		
  NRF_TIMER2->TASKS_START = 1;               // Start TIMER2
	
}

/**@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)
{
    
    char data[10];
	  uint32_t i;
	
    for (i = 0; i < length; i++)
    {
        while(app_uart_put(p_data[i]) != NRF_SUCCESS);
			  data[i]=p_data[i];
    }
    while(app_uart_put('\n') != NRF_SUCCESS);
		// Added- For changing the baud rate dynamically
		if(strstr(data,"BAUD9600")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud9600;
			uart_init();
		}
		if(strstr(data,"BAUD57600")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud57600;
			uart_init();
		}
		if(strstr(data,"BAUD115200")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud115200;
			uart_init();
		}
		if(strstr(data,"BAUD38400")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud38400;
			uart_init();
		}
		if(strstr(data,"BAUD14400")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud14400;
			uart_init();
		}
		if(strstr(data,"BAUD19200")!=NULL)
		{
			app_uart_close();
			baud_rate= UART_BAUDRATE_BAUDRATE_Baud19200;
			uart_init();
		}
		// Added- For changing the baud rate dynamically
}
/**@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;
            
        case BLE_GAP_EVT_DISCONNECTED:
            err_code = bsp_indication_set(BSP_INDICATE_IDLE);
            APP_ERROR_CHECK(err_code);
						gap_params_init();
						//uart_init();
            m_conn_handle = BLE_CONN_HANDLE_INVALID;
            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_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;

        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.
    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:
            err_code = ble_advertising_restart_without_whitelist();
            if (err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            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 '\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)
{
    uint8_t   tempByte;
    switch (p_event->evt_type)
    {
        case APP_UART_DATA_READY:
					
          
           app_uart_get(&tempByte);
           StructQueueAdd(&UartQueue,tempByte);

           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,
        baud_rate //Used static variable for configuring baud rate dynamically
		};

    APP_UART_FIFO_INIT( &comm_params,
                       UART_RX_BUF_SIZE,
                       UART_TX_BUF_SIZE,
                       uart_event_handle,
                       APP_IRQ_PRIORITY_LOW,
                       err_code);
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for initializing the Advertising functionality.
 */
static void advertising_init(void)
{
    uint32_t      err_code;
    ble_advdata_t advdata;
    ble_advdata_t scanrsp;

    // 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_GENERAL_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;

    ble_adv_modes_config_t options = {0};
    options.ble_adv_fast_enabled  = BLE_ADV_FAST_ENABLED;
    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 Application main function.
 */
int main(void)
{
    uint32_t err_code;
    bool erase_bonds;
  	uint8_t index=0;
    uint16_t  icounter =0; 
    
    // 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();
    
    StructQueueInit (&UartQueue);
	  printf("\r\nUART Start!\r\n");
    err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
    APP_ERROR_CHECK(err_code);
    start_timer();
    nrf_delay_ms(1000);
    // Enter main loop.
    	for (;;)
     {
       icounter++;
			 //printf("\r\n Count %u\r\n",icounter);
			 if(( icounter > 10000))
 
			 {
           err_code = ble_nus_string_send(&m_nus, data_array,index);
           index = 0;
           icounter = 0;
           // printf("\r\n 2 byteCount %u\r\n",bytereceivedCount);
         }
			   while(UartQueue.count >0)
         {
          StructQueueRemove(&UartQueue,&data_array[index++]);
         }
         
         if( index > 16)
         {
           err_code = ble_nus_string_send(&m_nus, data_array,index);
           //printf("\r\n 1 index %u\r\n",index);
           index = 0;
           icounter = 0;
         }
         
        
         power_manage();
		 }
		
    }
/** 
 * @}
 */ 

[haakonsh]

Use our macro for setting the minimum and maximum connection interval. As of now you are assigning the value 7.5 to an uint16_t which makes no sense. 

You should set:
#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(20, UNIT_1_25_MS)

#define MAX_CONN_INTERVAL              MSEC_TO_UNITS(75, UNIT_1_25_MS)

Use these settings before you start to optimize you latency. 

 

I will also recommend using UARTE with flow control. Then you'll get an event when the UART transmission is complete, instead of checking every receive byte for a newline.