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iOS MTU size why only 185 bytes

Hi,

I am writing an APP for comunicating with my nRF peripheral. I've set the MTU size to 251 and this works fine under bluez or android.

But if I try it in iOS (>10.0) I get only 185 bytes. Is there any way to increase it with DLE (data length extension).

So far the internet says no, but as I studied the BLE 4.2 standard it should be possible?

Best regards,

C.W.

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  • the example source code is attached.

    /**
     * Copyright (c) 2014 - 2017, Nordic Semiconductor ASA
     * 
     * All rights reserved.
     * 
     * Redistribution and use in source and binary forms, with or without modification,
     * are permitted provided that the following conditions are met:
     * 
     * 1. Redistributions of source code must retain the above copyright notice, this
     *    list of conditions and the following disclaimer.
     * 
     * 2. Redistributions in binary form, except as embedded into a Nordic
     *    Semiconductor ASA integrated circuit in a product or a software update for
     *    such product, must reproduce the above copyright notice, this list of
     *    conditions and the following disclaimer in the documentation and/or other
     *    materials provided with the distribution.
     * 
     * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
     *    contributors may be used to endorse or promote products derived from this
     *    software without specific prior written permission.
     * 
     * 4. This software, with or without modification, must only be used with a
     *    Nordic Semiconductor ASA integrated circuit.
     * 
     * 5. Any software provided in binary form under this license must not be reverse
     *    engineered, decompiled, modified and/or disassembled.
     * 
     * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
     * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     * 
     */
    /** @file
     *
     * @defgroup ble_sdk_uart_over_ble_main main.c
     * @{
     * @ingroup  ble_sdk_app_its_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 "nrf_ble_gatt.h"
    #include "app_timer.h"
    #include "app_button.h"
    #include "app_uart.h"
    #include "app_util_platform.h"
    #include "bsp.h"
    #include "bsp_btn_ble.h"
    #include "ble_image_transfer_service.h"
    #include "nrf_gpio.h"
    #include "cl_includes.h"
    #include "cl_system.h"
    #include "cl_hal_gpio.h"
    #include "ArducamMini2MP.h"
    
    #define NRF_LOG_MODULE_NAME "APP"
    #include "nrf_log.h"
    #include "nrf_log_ctrl.h"
    
    #define PCA10056_USE_FRONT_HEADER				0																						/**< Use the front header (P24) for the camera module. Requires SB10-15 and SB20-25 to be soldered/cut, as described in the readme. */
    
    #define CONN_CFG_TAG                    1                                           /**< A tag that refers to the BLE stack configuration we set with @ref sd_ble_cfg_set. Default tag is @ref BLE_CONN_CFG_TAG_DEFAULT. */
    
    #define APP_FEATURE_NOT_SUPPORTED       BLE_GATT_STATUS_ATTERR_APP_BEGIN + 2        /**< Reply when unsupported features are requested. */
    
    #define DEVICE_NAME                     "Nordic2IMAGE"                              /**< Name of device. Will be included in the advertising data. */
    #define ITS_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 MIN_CONN_INTERVAL               MSEC_TO_UNITS(15, UNIT_1_25_MS)              /**< Minimum acceptable connection interval (20 ms), Connection interval uses 1.25 ms units. */
    #define MAX_CONN_INTERVAL               MSEC_TO_UNITS(15, 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)                       /**< 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 MTU_REQUEST_DELAY                 APP_TIMER_TICKS(2000)                      /**< Battery level measurement interval (ticks). */
    
    #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. */
    APP_TIMER_DEF(m_MTU_request_timer_id);                        /**< Battery timer. */
    
    static ble_its_t                        m_its;                                      /**< Structure to identify the Nordic UART Service. */
    static uint16_t                         m_conn_handle = BLE_CONN_HANDLE_INVALID;    /**< Handle of the current connection. */
    
    static nrf_ble_gatt_t                   m_gatt;                                     /**< GATT module instance. */
    static ble_uuid_t                       m_adv_uuids[] = {{BLE_UUID_ITS_SERVICE, ITS_SERVICE_UUID_TYPE}};  /**< Universally unique service identifier. */
    static uint16_t                         m_ble_its_max_data_len = BLE_GATT_ATT_MTU_DEFAULT - 3;  /**< Maximum length of data (in bytes) that can be transmitted to the peer by the Nordic UART service module. */
    
    static uint8_t                          m_new_command_received = 0;
    static uint8_t                          m_new_resolution, m_new_phy;
    
    static bool                             m_stream_mode_active = false;
    
    static ble_its_ble_params_info_t        m_ble_params_info = {20, 50, 1, 1};
    static bool MTU_requested_flag = false;
    using namespace CppLib;
    
    ArducamMini2MP myCamera;
    Button button1(BUTTON_1, true);
    
    enum {APP_CMD_NOCOMMAND = 0, APP_CMD_SINGLE_CAPTURE, APP_CMD_START_STREAM, APP_CMD_STOP_STREAM, 
          APP_CMD_CHANGE_RESOLUTION, APP_CMD_CHANGE_PHY, APP_CMD_SEND_BLE_PARAMS};
    
    /**@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_its    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 its_data_handler(ble_its_t * p_its, uint8_t * p_data, uint16_t length)
    {
       
        switch(p_data[0])
        {
            // Take picture
            case APP_CMD_SINGLE_CAPTURE:
            case APP_CMD_SEND_BLE_PARAMS:
                m_new_command_received = p_data[0];
                break;
            
            case APP_CMD_START_STREAM:
                m_stream_mode_active = true;
                m_new_command_received = p_data[0];
                break;
    
            case APP_CMD_STOP_STREAM:
                m_stream_mode_active = false;
                m_new_command_received = p_data[0];
                break;
            
            case APP_CMD_CHANGE_RESOLUTION:
                m_new_command_received = APP_CMD_CHANGE_RESOLUTION;
                m_new_resolution = p_data[1];
                break;
            
            case APP_CMD_CHANGE_PHY:
                m_new_command_received = APP_CMD_CHANGE_PHY;
                m_new_phy = p_data[1];
                break;
            
            default: 
                printf("Unknown command!!\r\n");
                break;
        }
    }
    /**@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_its_init_t its_init;
    
        memset(&its_init, 0, sizeof(its_init));
    
        its_init.data_handler = its_data_handler;
    
        err_code = ble_its_init(&m_its, &its_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;
                
                printf("Connected\r\n");
                // iOS+Android support fix
                err_code = app_timer_start(m_MTU_request_timer_id, MTU_REQUEST_DELAY, NULL);
                APP_ERROR_CHECK(err_code);
                /*  err_code = sd_ble_gattc_exchange_mtu_request(m_conn_handle, 247);
           APP_ERROR_CHECK(err_code);*/
    
    
                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;
                
                // Set the command to have the resolution returned to the default 320x240
                m_new_command_received = APP_CMD_CHANGE_RESOLUTION;
                m_new_resolution = 1;
                
                m_stream_mode_active = false;
                m_ble_params_info.tx_phy = m_ble_params_info.rx_phy = 1;
                MTU_requested_flag=false;
                printf("Disconnected\r\n");
                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_GAP_EVT_DATA_LENGTH_UPDATE_REQUEST:
            {
                ble_gap_data_length_params_t dl_params;
    
                // Clearing the struct will effectivly set members to @ref BLE_GAP_DATA_LENGTH_AUTO
                memset(&dl_params, 0, sizeof(ble_gap_data_length_params_t));
                err_code = sd_ble_gap_data_length_update(p_ble_evt->evt.gap_evt.conn_handle, &dl_params, NULL);
                APP_ERROR_CHECK(err_code);
            } break;
    
            case BLE_GAP_EVT_CONN_PARAM_UPDATE:
            {
                uint16_t max_con_int = p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.max_conn_interval;
                uint16_t min_con_int = p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.min_conn_interval;
    
                m_ble_params_info.con_interval = max_con_int;
                ble_its_ble_params_info_send(&m_its, &m_ble_params_info);
                printf("Con params updated: CI %i, %i\r\n", (int)min_con_int, (int)max_con_int);
            } break;
           
            case BLE_GAP_EVT_PHY_UPDATE:
                m_ble_params_info.tx_phy = p_ble_evt->evt.gap_evt.params.phy_update.tx_phy;
                m_ble_params_info.rx_phy = p_ble_evt->evt.gap_evt.params.phy_update.rx_phy;    
                ble_its_ble_params_info_send(&m_its, &m_ble_params_info);
                printf("Phy update: %i, %i\r\n", (int)m_ble_params_info.tx_phy, (int)m_ble_params_info.rx_phy);
                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; // 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
            case BLE_GATTS_EVT_EXCHANGE_MTU_REQUEST:
                MTU_requested_flag=true;
                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);
        nrf_ble_gatt_on_ble_evt(&m_gatt, p_ble_evt);
        ble_its_on_ble_evt(&m_its, 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;
    
        clock_lf_cfg.source        = NRF_CLOCK_LF_SRC_XTAL;
        clock_lf_cfg.rc_ctiv       = 0;
        clock_lf_cfg.rc_temp_ctiv  = 0;
    #ifdef S140
        clock_lf_cfg.xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM;
    #else
        clock_lf_cfg.accuracy = NRF_CLOCK_LF_ACCURACY_20_PPM;
    #endif
    
        // Initialize SoftDevice.
        SOFTDEVICE_HANDLER_INIT(&clock_lf_cfg, NULL);
    
        // Fetch the start address of the application RAM.
        uint32_t ram_start = 0;
        err_code = softdevice_app_ram_start_get(&ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Overwrite some of the default configurations for the BLE stack.
        ble_cfg_t ble_cfg;
    
        // Configure the maximum number of connections.
        memset(&ble_cfg, 0, sizeof(ble_cfg));
        ble_cfg.gap_cfg.role_count_cfg.periph_role_count  = BLE_GAP_ROLE_COUNT_PERIPH_DEFAULT;
        ble_cfg.gap_cfg.role_count_cfg.central_role_count = 0;
        ble_cfg.gap_cfg.role_count_cfg.central_sec_count  = 0;
        err_code = sd_ble_cfg_set(BLE_GAP_CFG_ROLE_COUNT, &ble_cfg, ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Configure the maximum ATT MTU.
        memset(&ble_cfg, 0x00, sizeof(ble_cfg));
        ble_cfg.conn_cfg.conn_cfg_tag                 = CONN_CFG_TAG;
        ble_cfg.conn_cfg.params.gatt_conn_cfg.att_mtu = NRF_BLE_GATT_MAX_MTU_SIZE;
        err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATT, &ble_cfg, ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Configure the maximum event length.
        memset(&ble_cfg, 0x00, sizeof(ble_cfg));
        ble_cfg.conn_cfg.conn_cfg_tag                     = CONN_CFG_TAG;
        ble_cfg.conn_cfg.params.gap_conn_cfg.event_length = 320;
        ble_cfg.conn_cfg.params.gap_conn_cfg.conn_count   = BLE_GAP_CONN_COUNT_DEFAULT;
        err_code = sd_ble_cfg_set(BLE_CONN_CFG_GAP, &ble_cfg, ram_start);
        APP_ERROR_CHECK(err_code);
    
        // Enable BLE stack.
        err_code = softdevice_enable(&ram_start);
        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 GATT library. */
    void gatt_evt_handler(nrf_ble_gatt_t * p_gatt, const nrf_ble_gatt_evt_t * p_evt)
    {
        if ((m_conn_handle == p_evt->conn_handle) && (p_evt->evt_id == NRF_BLE_GATT_EVT_ATT_MTU_UPDATED))
        {
            m_ble_its_max_data_len = p_evt->params.att_mtu_effective - OPCODE_LENGTH - HANDLE_LENGTH;
            m_ble_params_info.mtu = m_ble_its_max_data_len;
            ble_its_ble_params_info_send(&m_its, &m_ble_params_info);
            printf("Data len is set to 0x%X(%d), or maybe %i\r\n", m_ble_its_max_data_len, m_ble_its_max_data_len, p_evt->params.data_length);
        }
        printf("ATT MTU exchange completed. central %i peripheral %i\r\n", p_gatt->att_mtu_desired_central, p_gatt->att_mtu_desired_periph);
    }
    
    
    /**@brief Function for initializing the GATT library. */
    void gatt_init(void)
    {
        ret_code_t err_code;
    
        err_code = nrf_ble_gatt_init(&m_gatt, gatt_evt_handler);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_ble_gatt_att_mtu_periph_set(&m_gatt, 64);
        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;
                
            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' '\n' (hex 0x0A) or if the string has reached the maximum 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_ITS_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 >= (m_ble_its_max_data_len)))
                {
                    NRF_LOG_DEBUG("Ready to send data over BLE NUS\r\n");
                    NRF_LOG_HEXDUMP_DEBUG(data_array, index);
    
                    do
                    {
                        err_code = ble_its_string_send(&m_its, data_array, index);
                        if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
                        {
                            APP_ERROR_CHECK(err_code);
                        }
                    } while (err_code == NRF_ERROR_BUSY);
    
                    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;
        app_uart_comm_params_t comm_params;
        comm_params.rx_pin_no    = RX_PIN_NUMBER;
        comm_params.tx_pin_no    = TX_PIN_NUMBER;
        comm_params.rts_pin_no   = RTS_PIN_NUMBER;
        comm_params.cts_pin_no   = CTS_PIN_NUMBER;
        comm_params.flow_control = APP_UART_FLOW_CONTROL_DISABLED;
        comm_params.use_parity   = false;
        comm_params.baud_rate    = 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);
    
        ble_advertising_conn_cfg_tag_set(CONN_CFG_TAG);
    }
    
    
    static void data_len_ext_set(bool status)
    {
        uint8_t data_length = status ? (247 + 4) : (23 + 4);
        (void) nrf_ble_gatt_data_length_set(&m_gatt, BLE_CONN_HANDLE_INVALID, data_length);
    }
    
    
    static void gatt_mtu_set(uint16_t att_mtu)
    {
        ret_code_t err_code;
    
        err_code = nrf_ble_gatt_att_mtu_periph_set(&m_gatt, att_mtu);
        APP_ERROR_CHECK(err_code);
    
        err_code = nrf_ble_gatt_att_mtu_central_set(&m_gatt, att_mtu);
        APP_ERROR_CHECK(err_code);
    }
    
    
    /**@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);
    }
    
    static void camera_init(void)
    {
    #if defined(BOARD_PCA10056)
    	#if(PCA10056_USE_FRONT_HEADER == 1)
    			myCamera.pinScl = 13;
    			myCamera.pinSda = 15;
    			myCamera.pinSck = 21;
    			myCamera.pinMiso = 23;
    			myCamera.pinMosi = 25;
    			myCamera.pinCsn = 32 + 9;
    	#else
    			myCamera.pinScl = 27;
    			myCamera.pinSda = 26;
    			myCamera.pinSck = 32 + 15;
    			myCamera.pinMiso = 32 + 14;
    			myCamera.pinMosi = 32 + 13;
    			myCamera.pinCsn = 32 + 12;
    	#endif
    #elif defined(BOARD_PCA10040)
        myCamera.pinScl = 27;
        myCamera.pinSda = 26;
        myCamera.pinSck = 25;
        myCamera.pinMiso = 24;
        myCamera.pinMosi = 23;
        myCamera.pinCsn = 22;
    #else
    #error Board not defined or not supported
    #endif    
        myCamera.open();
        myCamera.setResolution(OV2640_320x240);
    }
    
    
    /**@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);
    }
    
    
    void cpplibLogFunction(LogSeverity severity, char *module, uint32_t errorCode, char *message)
    {
        printf("%s - %s\r\n", module, message);
    }
    
    static void MTU_request_timeout_handler(void * p_context)
    { 
        ret_code_t err_code;
        if (!MTU_requested_flag) 
        {
           err_code = sd_ble_gattc_exchange_mtu_request(m_conn_handle, 247);
           //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)
    {
        ret_code_t err_code;
    
        // Initialize timer module.
        err_code = app_timer_init();
        APP_ERROR_CHECK(err_code);
    
        // Create timers.
        err_code = app_timer_create(&m_MTU_request_timer_id,
                                    APP_TIMER_MODE_SINGLE_SHOT,
                                    MTU_request_timeout_handler);
        APP_ERROR_CHECK(err_code);
    }
    
    /**@brief Application main function.
     */
    int main(void)
    {
        uint32_t err_code;
        uint32_t img_data_length = 0;
        uint8_t img_data_buffer[255];
    
        // Initialize.
       
        timers_init();
        uart_init();
        log_init();
     
    
        // Start application timers.
      
        ble_stack_init();
        gap_params_init();
        gatt_init();
        services_init();
        advertising_init();
        conn_params_init();
        
        printf("\r\nUART Start!\r\n");
    
        nrfSystem.setLogHandler(cpplibLogFunction);
        nrfSystem.setLogDefaultSeverity(LS_DEBUG);
        err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
        APP_ERROR_CHECK(err_code);
    
        camera_init();
    
        data_len_ext_set(true);
    
        gatt_mtu_set(247);
    
        // Enter main loop.
        for (;;)
        {
            uint32_t image_size;
            ble_gap_phys_t gap_phys_settings;    
    
            switch(m_new_command_received)
            {
                case APP_CMD_SINGLE_CAPTURE:
                    m_new_command_received = APP_CMD_NOCOMMAND;
                    //ble_its_send_file(&m_its, test_file, TEST_FILE_SIZE);
                    if(myCamera.bytesAvailable() == 0)
                    {
                        printf("Starting capture...\r\n");
                        myCamera.startSingleCapture();
                        image_size = myCamera.bytesAvailable();
                        printf("Capture complete: size %i bytes\r\n", (int)(image_size));
                        ble_its_img_info_t image_info;
                        image_info.file_size_bytes = image_size - 1;
                        ble_its_img_info_send(&m_its, &image_info);
                        
                        // Flush the first byte (or the JPG image will be corrupted)
                        myCamera.fillBuffer(img_data_buffer, 1);
                    }
                    break;
                
                case APP_CMD_START_STREAM:
                    m_new_command_received = APP_CMD_NOCOMMAND;
    
                    printf("Stream mode enabled\r\n");                
                    break;
                    
                case APP_CMD_STOP_STREAM:
                    m_new_command_received = APP_CMD_NOCOMMAND;
                    m_stream_mode_active = false;
                    printf("Stream mode disabled\r\n");
                    break;
                    
                case APP_CMD_CHANGE_RESOLUTION:
                    m_new_command_received = APP_CMD_NOCOMMAND;
                    printf("Change resolution to mode: %i\r\n", (int)m_new_resolution);
                    switch(m_new_resolution)
                    {
                        case 0:
                            myCamera.setResolution(OV2640_160x120);
                            break;
                        
                        case 1:
                            myCamera.setResolution(OV2640_320x240);
                            break;
    
                        case 2:
                            myCamera.setResolution(OV2640_640x480);
                            break;
    
                        case 3:
                            myCamera.setResolution(OV2640_800x600);
                            break;
    
                        case 4:
                            myCamera.setResolution(OV2640_1024x768);
                            break;
                        
                        case 5:
                            myCamera.setResolution(OV2640_1600x1200);
                            break;
                        
                    } 
                    break;
                    
                case APP_CMD_CHANGE_PHY:   
                    m_new_command_received = APP_CMD_NOCOMMAND;
                
                    printf("Attempting to change phy.\r\n");
                    gap_phys_settings.tx_phys = (m_new_phy == 0 ? BLE_GAP_PHY_1MBPS : BLE_GAP_PHY_2MBPS);  
                    gap_phys_settings.rx_phys = (m_new_phy == 0 ? BLE_GAP_PHY_1MBPS : BLE_GAP_PHY_2MBPS);  
    #ifdef S140            
                    sd_ble_gap_phy_request(m_its.conn_handle, &gap_phys_settings);   
    #else            
                    sd_ble_gap_phy_update(m_its.conn_handle, &gap_phys_settings);  
    #endif
                    break;
                
                case APP_CMD_SEND_BLE_PARAMS:
                    m_new_command_received = APP_CMD_NOCOMMAND;
                    ble_its_ble_params_info_send(&m_its, &m_ble_params_info);
                    break;
                
                default:
                    break;
            }
            
            if(m_stream_mode_active)
            {
                if(img_data_length == 0 && myCamera.bytesAvailable() == 0)
                {
                    myCamera.startSingleCapture();
    
                    image_size = myCamera.bytesAvailable();
                    
                    ble_its_img_info_t image_info;
                    image_info.file_size_bytes = image_size - 1;
                    ble_its_img_info_send(&m_its, &image_info);
                    
                    // Flush the first byte (or the JPG image will be corrupted)
                    myCamera.fillBuffer(img_data_buffer, 1);
                }
            }
            
            if(img_data_length > 0 || myCamera.bytesAvailable() > 0)
            {
                if(img_data_length == 0)
                {
                    img_data_length = myCamera.fillBuffer(img_data_buffer, m_ble_its_max_data_len);
                }
                if(ble_its_send_file_fragment(&m_its, img_data_buffer, img_data_length) == NRF_SUCCESS)
                {
                    img_data_length = 0;
                }                
            }
            
            if(m_new_command_received == APP_CMD_NOCOMMAND)
            {
                power_manage();
            }
        }
    }
    
    
    /**
     * @}
     */
    

  • Hi,

    i've tried your example but it did not change something. I've added

    data_len_ext_set(true);
    gatt_mtu_set(NRF_SDH_BLE_GATT_MAX_MTU_SIZE);

    But I can still only get 185 bytes. What I am missig?

    My data:

    nRF52832 dev board

    SDK 14.2

    Softdevice S132

    This is the order I am calling the routines

        bool erase_bonds;
        ret_code_t err_code;

        log_init();
        NRF_LOG_INFO("firmware compilation date and time: %s %s", __DATE__, __TIME__);
        #if defined BOARD_CUSTOM
            NRF_LOG_INFO("BOARD_CUSTOM");
        #elif defined BOARD_PCA10040
            NRF_LOG_INFO("BOARD_PCA10040");
        #endif

        timers_init();
        buttons_leds_init(&erase_bonds);
        ble_stack_init();
        gap_params_init();
        gatt_init();
        gpio_init();

        peer_manager_init();
        //services_init();

        // initialization of communication handler
        CommHandler* communication_handler = CommHandler::getInstance();
        communication_handler->nus_initialize_instance(&m_nus);

        advertising_init();
        conn_params_init();
        advertising_start(erase_bonds);

        data_len_ext_set(true);
        gatt_mtu_set(NRF_SDH_BLE_GATT_MAX_MTU_SIZE);

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