Time-sensitive: BLE packet size limited to 64 bytes even though MTU size negotiated to 244 bytes

Question

Hi everyone - thank you in advance for your support with this. 
 Our team's goal is to sample ADC data on a single channel at a sample rate of 500 Hz and send that to a laptop via BLE. 
 System: - Transmitter: nrf52DK (nrf52832) 
 - Receiver: laptop (Python script) 
 
 I started with the example in: https://github.com/NordicPlayground/nRF52-ADC-examples/blob/master/ble_app_uart__saadc_timer_driven__scan_mode/main.c . I'm programming the dev board using Segger Embedded Studio. 
 I modified the example to sample on only one channel and at a rate of 500 Hz. I (ideally) want to also send that data a rate of 500 samples/second; in the example, sampling and sending are both happening inside the callback, so I moved the sending logic into a separate method and created a ring buffer that would populate with SAADC samples and send at various intervals. 
 My issue at the moment is that even though the negotiated MTU size between central and peripheral is 244 bytes (verified by printing m_ble_nus_max_data_len after negotiation and immediately before sending - I can see the value change from 20 bytes to 244 bytes when the connection is established), my receiver (which is a simple Python script that simply prints out the packet exactly as it's received) seems to only be receiving a maximum of 64 bytes per packet. I wrote a minimal example that attempts to send a simple buffer that is 244 bytes long (attempted with integers, repeating characters, binary data), but see the same issue of only receiving 64 bytes per packet. 
 I don't want to continue development until I can verify that at least one packet is being sent and received exactly as expected, so ideally want to see 244 bytes being sent and received in a single packet before continuing. My idea is that after I can confirm that I can send 244 bytes per packet, I can then package the 500 samples into appropriate packets and send them in single packets to my receiver. If there's a better way to implement this, I would love to hear that too. 
 I'm new to both Nordic and bluetooth communication in general so would really appreciate your support with this; I've been struggling with it for a while and this is actively stopping a high-priority project's development. 
 Thanks so much, appreciate your support.

Vidar Berg · Accepted Answer

Hi,

I'm not familiar with the Adafruit library, unfortunately. However, I'm glad to hear that it worked with Bleak. I tested with the example you mentioned and was able to send 500 SAADC samples per second to my PC.

Modified main.c

/**
 * Copyright (c) 2014 - 2018, 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
 * Peripheral: SAADC
 * Compatibility: nRF52832 rev 2/nRF52840 rev 1, SDK 15.2.0
 * Softdevice used: S132 v6.1.0/S140 v6.1.0
 *
 * This SAADC example samples on 4 different input pins, and enables scan mode to do that. It is otherwise an
 * offsprint from the standard ble_app_uart example available in nRF5 SDK 15.2.0
 * Works together with softdevice S132 v6.1.0 on nRF52832 and S140 v6.1.0 on nRF52840
 * Transmits SAADC output to hardware UART and over BLE via Nordic UART Servive (NUS).
 * Info on NUS -> http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v13.0.0/ble_sdk_app_nus_eval.html?cp=4_0_0_4_1_2_17
 * Info on hardware UART settings -> http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v13.0.0/uart_example.html?cp=4_0_0_4_4_41
 */


#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 "nrf_sdh.h"
#include "nrf_sdh_soc.h"
#include "nrf_sdh_ble.h"
#include "nrf_ble_gatt.h"
#include "nrf_ble_qwr.h"
#include "app_timer.h"
#include "ble_nus.h"
#include "app_uart.h"
#include "app_util_platform.h"
#include "bsp_btn_ble.h"
#include "nrf_pwr_mgmt.h"
#include "nrf_drv_saadc.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_timer.h"

#if defined (UART_PRESENT)
#include "nrf_uart.h"
#endif
#if defined (UARTE_PRESENT)
#include "nrf_uarte.h"
#endif

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

#define APP_BLE_CONN_CFG_TAG            1                                           /**< A tag identifying the SoftDevice BLE configuration. */

#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_BLE_OBSERVER_PRIO           3                                           /**< Application's BLE observer priority. You shouldn't need to modify this value. */

#define APP_ADV_INTERVAL                64                                          /**< The advertising interval (in units of 0.625 ms. This value corresponds to 40 ms). */

#define APP_ADV_DURATION                18000                                       /**< The advertising duration (180 seconds) in units of 10 milliseconds. */

#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)                       /**< 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 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 SAADC_SAMPLES_IN_BUFFER         1
#define SAADC_SAMPLE_RATE               2                                         /**< SAADC sample rate in ms. */               

#define ADC_REF_VOLTAGE_IN_MILLIVOLTS   600                                     /**< Reference voltage (in milli volts) used by ADC while doing conversion. */
#define ADC_PRE_SCALING_COMPENSATION    6                                       /**< The ADC is configured to use VDD with 1/3 prescaling as input. And hence the result of conversion is to be multiplied by 3 to get the actual value of the battery voltage.*/
#define DIODE_FWD_VOLT_DROP_MILLIVOLTS  270                                     /**< Typical forward voltage drop of the diode . */
#define ADC_RES_12BIT                   4096                                    /**< Maximum digital value for 10-bit ADC conversion. */

/**@brief Macro to convert the result of ADC conversion in millivolts.
 *
 * @param[in]  ADC_VALUE   ADC result.
 *
 * @retval     Result converted to millivolts.
 */
#define ADC_RESULT_IN_MILLI_VOLTS(ADC_VALUE)\
        ((((ADC_VALUE) * ADC_REF_VOLTAGE_IN_MILLIVOLTS) / ADC_RES_12BIT) * ADC_PRE_SCALING_COMPENSATION)

/* Defines the maximum number of samples that can be included in the BLE notification packet. */
#define MAX_SAMPLES_NOTIFICATION   (NRF_SDH_BLE_GATT_MAX_MTU_SIZE - 3) / sizeof(nrf_saadc_value_t)  

BLE_NUS_DEF(m_nus, NRF_SDH_BLE_TOTAL_LINK_COUNT);                                   /**< BLE NUS service instance. */
NRF_BLE_GATT_DEF(m_gatt);                                                           /**< GATT module instance. */
NRF_BLE_QWR_DEF(m_qwr);                                                             /**< Context for the Queued Write module.*/
BLE_ADVERTISING_DEF(m_advertising);
APP_TIMER_DEF(m_throughput_timer_id);                                                 /**< Advertising module instance. */

static uint16_t   m_conn_handle          = BLE_CONN_HANDLE_INVALID;                 /**< Handle of the current connection. */
static uint16_t   m_ble_nus_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 ble_uuid_t m_adv_uuids[]          =                                          /**< Universally unique service identifier. */
{
    {BLE_UUID_NUS_SERVICE, NUS_SERVICE_UUID_TYPE}
};

volatile uint8_t state = 1;

static const nrf_drv_timer_t   m_timer = NRF_DRV_TIMER_INSTANCE(3);
static nrf_saadc_value_t       m_buffer_pool[2][SAADC_SAMPLES_IN_BUFFER];
static nrf_ppi_channel_t       m_ppi_channel;
static uint32_t                m_adc_evt_counter;

static uint32_t samples_sent;
static nrf_saadc_value_t ble_sample_buffer[MAX_SAMPLES_NOTIFICATION];

static void throughput_timer_start(void)
{
    ret_code_t err_code;

    err_code = app_timer_start(m_throughput_timer_id, APP_TIMER_TICKS(10000), NULL);
    APP_ERROR_CHECK(err_code);
}

static void throughput_timer_stop(void)
{
    ret_code_t err_code;
    err_code = app_timer_stop(m_throughput_timer_id);
    APP_ERROR_CHECK(err_code);
}

static void throughput_timeout_handler (void * p_context)
{
    NRF_LOG_INFO("%d samples/second", samples_sent / 10);
    samples_sent = 0;
}



/**@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 initializing the timer module.
 */
static void timers_init(void)
{
    ret_code_t err_code = app_timer_init();
    APP_ERROR_CHECK(err_code);

    err_code = app_timer_create(&m_throughput_timer_id,
                                APP_TIMER_MODE_REPEATED,
                                throughput_timeout_handler);
    APP_ERROR_CHECK(err_code);
}

/**@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 Queued Write Module errors.
 *
 * @details A pointer to this function will be passed to each service which may need to inform the
 *          application about an error.
 *
 * @param[in]   nrf_error   Error code containing information about what went wrong.
 */
static void nrf_qwr_error_handler(uint32_t nrf_error)
{
    APP_ERROR_HANDLER(nrf_error);
}


/**@brief Function for 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_evt       Nordic UART Service event.
 */
/**@snippet [Handling the data received over BLE] */
static void nus_data_handler(ble_nus_evt_t * p_evt)
{

    if (p_evt->type == BLE_NUS_EVT_RX_DATA)
    {
        uint32_t err_code;

        NRF_LOG_DEBUG("Received data from BLE NUS. Writing data on UART.");
        NRF_LOG_HEXDUMP_DEBUG(p_evt->params.rx_data.p_data, p_evt->params.rx_data.length);

        for (uint32_t i = 0; i < p_evt->params.rx_data.length; i++)
        {
            do
            {
                err_code = app_uart_put(p_evt->params.rx_data.p_data[i]);
                if ((err_code != NRF_SUCCESS) && (err_code != NRF_ERROR_BUSY))
                {
                    NRF_LOG_ERROR("Failed receiving NUS message. Error 0x%x. ", err_code);
                    APP_ERROR_CHECK(err_code);
                }
            } while (err_code == NRF_ERROR_BUSY);
        }
        if (p_evt->params.rx_data.p_data[p_evt->params.rx_data.length - 1] == '\r')
        {
            while (app_uart_put('\n') == NRF_ERROR_BUSY);
        }
    }
    else if (p_evt->type == BLE_NUS_EVT_COMM_STARTED)
    {
        throughput_timer_start();
    }

}
/**@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;
    nrf_ble_qwr_init_t qwr_init = {0};

    // Initialize Queued Write Module.
    qwr_init.error_handler = nrf_qwr_error_handler;

    err_code = nrf_ble_qwr_init(&m_qwr, &qwr_init);
    APP_ERROR_CHECK(err_code);

    // Initialize NUS.
    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 handling BLE events.
 *
 * @param[in]   p_ble_evt   Bluetooth stack event.
 * @param[in]   p_context   Unused.
 */
static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
    uint32_t err_code;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
            NRF_LOG_INFO("Connected");
            err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
            APP_ERROR_CHECK(err_code);
            m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
            err_code = nrf_ble_qwr_conn_handle_assign(&m_qwr, m_conn_handle);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_GAP_EVT_DISCONNECTED:
            NRF_LOG_INFO("Disconnected");
            // LED indication will be changed when advertising starts.
            m_conn_handle = BLE_CONN_HANDLE_INVALID;
            throughput_timer_stop();
            break;

        case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
        {
            NRF_LOG_DEBUG("PHY update request.");
            ble_gap_phys_t const phys =
            {
                .rx_phys = BLE_GAP_PHY_AUTO,
                .tx_phys = BLE_GAP_PHY_AUTO,
            };
            err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
            APP_ERROR_CHECK(err_code);
        } break;

        case BLE_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;

        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;

        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;

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


/**@brief Function for the SoftDevice initialization.
 *
 * @details This function initializes the SoftDevice and the BLE event interrupt.
 */
static void ble_stack_init(void)
{
    ret_code_t err_code;

    err_code = nrf_sdh_enable_request();
    APP_ERROR_CHECK(err_code);

    // Configure the BLE stack using the default settings.
    // Fetch the start address of the application RAM.
    uint32_t ram_start = 0;
    err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
    APP_ERROR_CHECK(err_code);

    // Enable BLE stack.
    err_code = nrf_sdh_ble_enable(&ram_start);
    APP_ERROR_CHECK(err_code);

    // Register a handler for BLE events.
    NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
}


/**@brief Function for handling events from the GATT library. */
void gatt_evt_handler(nrf_ble_gatt_t * p_gatt, nrf_ble_gatt_evt_t const * p_evt)
{
    if ((m_conn_handle == p_evt->conn_handle) && (p_evt->evt_id == NRF_BLE_GATT_EVT_ATT_MTU_UPDATED))
    {
        m_ble_nus_max_data_len = p_evt->params.att_mtu_effective - OPCODE_LENGTH - HANDLE_LENGTH;
        NRF_LOG_INFO("Data len is set to 0x%X(%d)", m_ble_nus_max_data_len, m_ble_nus_max_data_len);
    }
    NRF_LOG_DEBUG("ATT MTU exchange completed. central 0x%x peripheral 0x%x",
                  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, NRF_SDH_BLE_GATT_MAX_MTU_SIZE);
    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(&m_advertising);
                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_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') ||
                (data_array[index - 1] == '\r') ||
                (index >= m_ble_nus_max_data_len))
            {
                if (index > 1)
                {
                    NRF_LOG_DEBUG("Ready to send data over BLE NUS");
                    NRF_LOG_HEXDUMP_DEBUG(data_array, index);

                    do
                    {
                        uint16_t length = (uint16_t)index;
                        err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
                        if ((err_code != NRF_ERROR_INVALID_STATE) &&
                            (err_code != NRF_ERROR_RESOURCES) &&
                            (err_code != NRF_ERROR_NOT_FOUND))
                        {
                            APP_ERROR_CHECK(err_code);
                        }
                    } while (err_code == NRF_ERROR_RESOURCES);
                }

                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 const comm_params =
    {
        .rx_pin_no    = RX_PIN_NUMBER,
        .tx_pin_no    = TX_PIN_NUMBER,
        .rts_pin_no   = RTS_PIN_NUMBER,
        .cts_pin_no   = CTS_PIN_NUMBER,
        .flow_control = APP_UART_FLOW_CONTROL_DISABLED,
        .use_parity   = false,
#if defined (UART_PRESENT)
        .baud_rate    = NRF_UART_BAUDRATE_115200
#else
        .baud_rate    = NRF_UARTE_BAUDRATE_115200
#endif
    };

    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_advertising_init_t init;

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

    init.advdata.name_type          = BLE_ADVDATA_FULL_NAME;
    init.advdata.include_appearance = false;
    init.advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_LIMITED_DISC_MODE;

    init.srdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
    init.srdata.uuids_complete.p_uuids  = m_adv_uuids;

    init.config.ble_adv_fast_enabled  = true;
    init.config.ble_adv_fast_interval = APP_ADV_INTERVAL;
    init.config.ble_adv_fast_timeout  = APP_ADV_DURATION;
    init.evt_handler = on_adv_evt;

    err_code = ble_advertising_init(&m_advertising, &init);
    APP_ERROR_CHECK(err_code);

    ble_advertising_conn_cfg_tag_set(&m_advertising, APP_BLE_CONN_CFG_TAG);
}


/**@brief Function for initializing buttons and leds.
 *
 * @param[out] p_erase_bonds  Will be true if the clear bonding button was pressed to wake the application up.
 */
static void buttons_leds_init(bool * p_erase_bonds)
{
    bsp_event_t startup_event;

    uint32_t err_code = bsp_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS, bsp_event_handler);
    APP_ERROR_CHECK(err_code);

    err_code = bsp_btn_ble_init(NULL, &startup_event);
    APP_ERROR_CHECK(err_code);

    *p_erase_bonds = (startup_event == BSP_EVENT_CLEAR_BONDING_DATA);
}


/**@brief Function for initializing the nrf log module.
 */
static void log_init(void)
{
    ret_code_t err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();
}


/**@brief Function for initializing power management.
 */
static void power_management_init(void)
{
    ret_code_t err_code;
    err_code = nrf_pwr_mgmt_init();
    APP_ERROR_CHECK(err_code);
}


/**@brief Function for handling the idle state (main loop).
 *
 * @details If there is no pending log operation, then sleep until next the next event occurs.
 */
static void idle_state_handle(void)
{
    UNUSED_RETURN_VALUE(NRF_LOG_PROCESS());
    nrf_pwr_mgmt_run();
}


/**@brief Function for starting advertising.
 */
static void advertising_start(void)
{
    uint32_t err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);
    APP_ERROR_CHECK(err_code);
}


void timer_handler(nrf_timer_event_t event_type, void* p_context)
{

}


void saadc_sampling_event_init(void)
{
    ret_code_t err_code;
    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);
    
    nrf_drv_timer_config_t timer_config = NRF_DRV_TIMER_DEFAULT_CONFIG;
    timer_config.frequency = NRF_TIMER_FREQ_1MHz;
    err_code = nrf_drv_timer_init(&m_timer, &timer_config, timer_handler);
    APP_ERROR_CHECK(err_code);

    /* setup m_timer for compare event */
    uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, SAADC_SAMPLE_RATE);
    nrf_drv_timer_extended_compare(&m_timer, NRF_TIMER_CC_CHANNEL0, ticks, NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK, false);
    nrf_drv_timer_enable(&m_timer);

    uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer, NRF_TIMER_CC_CHANNEL0);
    uint32_t saadc_sample_event_addr = nrf_drv_saadc_sample_task_get();

    /* setup ppi channel so that timer compare event is triggering sample task in SAADC */
    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
    APP_ERROR_CHECK(err_code);
    
    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel, timer_compare_event_addr, saadc_sample_event_addr);
    APP_ERROR_CHECK(err_code);
}


void saadc_sampling_event_enable(void)
{
    ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);
    APP_ERROR_CHECK(err_code);
}

static void update_buffer(nrf_saadc_value_t* p_current_buffer) 
{    
    nrf_saadc_value_t * p_new_buffer = 
        (p_current_buffer == m_buffer_pool[0]) ? m_buffer_pool[1] : m_buffer_pool[0];

    ret_code_t err_code = nrf_drv_saadc_buffer_convert(p_new_buffer, SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);
}

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
    if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        ret_code_t err_code;
        uint8_t max_samples;
        uint16_t length;
        nrf_saadc_value_t saadc_value;

        static uint16_t sample_cnt;
        
        update_buffer(p_event->data.done.p_buffer);
        
        saadc_value = ADC_RESULT_IN_MILLI_VOLTS(p_event->data.done.p_buffer[0]);
        memcpy(&ble_sample_buffer[sample_cnt++], &saadc_value, sizeof(nrf_saadc_value_t));
        
        max_samples = (m_ble_nus_max_data_len / sizeof(nrf_saadc_value_t));
  
        if (max_samples == sample_cnt)
        {
            length = sample_cnt * sizeof(nrf_saadc_value_t);

            err_code = ble_nus_data_send(&m_nus, (uint8_t *) ble_sample_buffer, &length, m_conn_handle);
            
            if ((err_code != NRF_ERROR_INVALID_STATE) && 
                (err_code != NRF_ERROR_NOT_FOUND) &&
                (err_code != NRF_ERROR_RESOURCES))
            {
                APP_ERROR_CHECK(err_code);
            }

            if (err_code == NRF_SUCCESS)
            {
                samples_sent += sample_cnt;
            }

            sample_cnt = 0;
        } 
        				
    }
}



void saadc_init(void)
{
    ret_code_t err_code;
	
    nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;
    saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
	
    nrf_saadc_channel_config_t channel_0_config =
        NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);
			
    err_code = nrf_drv_saadc_init(&saadc_config, saadc_callback);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_channel_init(0, &channel_0_config);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0],SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);   
}

/**@brief Application main function.
 */
int main(void)
{
    bool erase_bonds;

    // Initialize.
    uart_init();
    log_init();
    timers_init();
    buttons_leds_init(&erase_bonds);
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    services_init();
    advertising_init();
    conn_params_init();

    saadc_sampling_event_init();
    saadc_init();
    saadc_sampling_event_enable();

    // Start execution.
    printf("\r\nUART started.\r\n");
    NRF_LOG_INFO("Debug logging for UART over RTT started.");
    advertising_start();

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


/**
 * @}
 */

Log output nRF Side:

Python script

"""
UART Service
-------------

An example showing how to write a simple program using the Nordic Semiconductor
(nRF) UART service.

"""

import asyncio
import sys
import struct
from itertools import count, takewhile
from typing import Iterator

from bleak import BleakClient, BleakScanner
from bleak.backends.characteristic import BleakGATTCharacteristic
from bleak.backends.device import BLEDevice
from bleak.backends.scanner import AdvertisementData

UART_SERVICE_UUID = "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
UART_RX_CHAR_UUID = "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
UART_TX_CHAR_UUID = "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"


# TIP: you can get this function and more from the ``more-itertools`` package.
def sliced(data: bytes, n: int) -> Iterator[bytes]:
    """
    Slices *data* into chunks of size *n*. The last slice may be smaller than
    *n*.
    """
    return takewhile(len, (data[i : i + n] for i in count(0, n)))


async def uart_terminal():
    """This is a simple "terminal" program that uses the Nordic Semiconductor
    (nRF) UART service. It reads from stdin and sends each line of data to the
    remote device. Any data received from the device is printed to stdout.
    """

    def match_nus_uuid(device: BLEDevice, adv: AdvertisementData):
        # This assumes that the device includes the UART service UUID in the
        # advertising data. This test may need to be adjusted depending on the
        # actual advertising data supplied by the device.
        if UART_SERVICE_UUID.lower() in adv.service_uuids:
            return True

        return False

    device = await BleakScanner.find_device_by_filter(match_nus_uuid)

    if device is None:
        print("no matching device found, you may need to edit match_nus_uuid().")
        sys.exit(1)

    def handle_disconnect(_: BleakClient):
        print("Device was disconnected, goodbye.")
        # cancelling all tasks effectively ends the program
        for task in asyncio.all_tasks():
            task.cancel()

    def handle_rx(_: BleakGATTCharacteristic, data: bytearray):
        #print("received:", data)
        ints = [struct.unpack('<h', data[i:i+2])[0] for i in range(0, len(data), 2)]
        print("Number of samples received:", len(ints))
        print("Samples values:", ints)

    async with BleakClient(device, disconnected_callback=handle_disconnect) as client:
        await client.start_notify(UART_TX_CHAR_UUID, handle_rx)

        print("Connected, start typing and press ENTER...")

        loop = asyncio.get_running_loop()
        nus = client.services.get_service(UART_SERVICE_UUID)
        rx_char = nus.get_characteristic(UART_RX_CHAR_UUID)

        while True:
            # This waits until you type a line and press ENTER.
            # A real terminal program might put stdin in raw mode so that things
            # like CTRL+C get passed to the remote device.
            data = await loop.run_in_executor(None, sys.stdin.buffer.readline)

            # data will be empty on EOF (e.g. CTRL+D on *nix)
            if not data:
                break

            # some devices, like devices running MicroPython, expect Windows
            # line endings (uncomment line below if needed)
            # data = data.replace(b"\n", b"\r\n")

            # Writing without response requires that the data can fit in a
            # single BLE packet. We can use the max_write_without_response_size
            # property to split the data into chunks that will fit.

            for s in sliced(data, rx_char.max_write_without_response_size):
                await client.write_gatt_char(rx_char, s, response=False)

            print("sent:", data)


if __name__ == "__main__":
    try:
        asyncio.run(uart_terminal())
    except asyncio.CancelledError:
        # task is cancelled on disconnect, so we ignore this error
        pass

Python log

Number of samples received: 122
Samples values: [2796, 2790, 2802, 2802, 2790, 2796, 2784, 2790, 2796, 2802, 2802, 2844, 2802, 2808, 2796, 2796, 2802, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2808, 2796, 2808, 2796, 2802, 2802, 2808, 2802, 2796, 2790, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2808, 2808, 2802, 2802, 2808, 2796, 2808, 2796, 2802, 2802, 2808, 2802, 2796, 2802, 2796, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2796, 2802, 2802, 2796, 2802, 2802, 2802, 2796, 2802, 2796, 2796, 2802, 2802, 2808, 2796, 2802, 2802, 2802, 2802, 2796, 2796, 2796, 2808, 2796, 2802, 2802, 2808, 2808, 2790, 2808, 2808, 2796, 2802, 2796, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2790, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2790, 2808, 2796, 2802]
Number of samples received: 122
Samples values: [2802, 2796, 2808, 2802, 2802, 2808, 2802, 2796, 2790, 2802, 2802, 2808, 2796, 2796, 2808, 2802, 2802, 2790, 2796, 2778, 2784, 2802, 2802, 2808, 2802, 2802, 2808, 2796, 2808, 2808, 2802, 2790, 2796, 2796, 2796, 2796, 2808, 2802, 2808, 2808, 2796, 2802, 2796, 2796, 2796, 2796, 2796, 2808, 2802, 2796, 2802, 2802, 2808, 2802, 2802, 2808, 2796, 2796, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2808, 2796, 2808, 2802, 2802, 2802, 2802, 2802, 2796, 2808, 2808, 2802, 2808, 2808, 2802, 2802, 2802, 2802, 2790, 2796, 2802, 2796, 2796, 2802, 2802, 2802, 2808, 2802, 2802, 2790, 2802, 2802, 2802, 2796, 2808, 2796, 2790, 2796, 2796, 2808, 2802, 2802, 2796, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2802]
Number of samples received: 122
Samples values: [2802, 2796, 2802, 2808, 2802, 2802, 2802, 2802, 2802, 2796, 2784, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2802, 2796, 2802, 2796, 2808, 2802, 2808, 2802, 2796, 2802, 2808, 2802, 2808, 2790, 2802, 2808, 2808, 2802, 2802, 2802, 2802, 2808, 2802, 2808, 2802, 2796, 2802, 2808, 2802, 2796, 2796, 2790, 2808, 2808, 2796, 2802, 2802, 2802, 2808, 2802, 2802, 2802, 2796, 2802, 2802, 2814, 2802, 2808, 2796, 2796, 2796, 2802, 2802, 2802, 2796, 2802, 2802, 2796, 2796, 2802, 2802, 2802, 2808, 2802, 2802, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2802, 2808, 2802, 2802, 2802, 2802, 2808, 2802, 2832, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2808, 2802, 2808, 2796, 2802, 2802, 2796, 2802, 2796, 2790, 2826, 2802, 2796, 2796]
Number of samples received: 122
Samples values: [2784, 2790, 2802, 2796, 2802, 2802, 2802, 2796, 2796, 2802, 2802, 2796, 2808, 2808, 2808, 2796, 2808, 2808, 2802, 2802, 2802, 2802, 2796, 2796, 2802, 2802, 2808, 2796, 2802, 2802, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2802, 2796, 2808, 2802, 2802, 2802, 2796, 2802, 2778, 2802, 2802, 2802, 2790, 2802, 2802, 2796, 2808, 2796, 2802, 2802, 2796, 2802, 2808, 2802, 2802, 2802, 2796, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2802, 2808, 2796, 2802, 2808, 2808, 2808, 2802, 2802, 2796, 2802, 2808, 2802, 2808, 2814, 2808, 2802, 2784, 2808, 2802, 2808, 2802, 2802, 2802, 2802, 2808, 2802, 2808, 2802, 2796, 2814, 2802, 2808, 2802, 2802, 2802, 2802, 2808, 2802, 2808, 2802, 2802, 2802, 2802, 2802, 2808, 2802, 2796, 2796]
Number of samples received: 122
Samples values: [2808, 2802, 2796, 2802, 2808, 2808, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2802, 2778, 2802, 2796, 2796, 2802, 2802, 2802, 2802, 2796, 2802, 2808, 2790, 2808, 2802, 2808, 2796, 2802, 2796, 2808, 2802, 2796, 2808, 2796, 2802, 2802, 2808, 2796, 2796, 2802, 2802, 2802, 2802, 2808, 2814, 2802, 2802, 2802, 2808, 2808, 2802, 2802, 2808, 2808, 2802, 2802, 2802, 2796, 2802, 2802, 2808, 2802, 2802, 2802, 2832, 2802, 2808, 2802, 2802, 2802, 2808, 2790, 2802, 2808, 2802, 2802, 2808, 2802, 2808, 2808, 2808, 2802, 2802, 2796, 2802, 2802, 2808, 2802, 2808, 2802, 2796, 2802, 2802, 2808, 2802, 2802, 2802, 2796, 2802, 2796, 2802, 2796, 2808, 2808, 2808, 2802, 2802, 2796, 2802, 2790, 2790, 2802, 2802, 2808, 2802, 2802, 2802, 2808, 2802]
Number of samples received: 122
Samples values: [2796, 2820, 2802, 2796, 2778, 2796, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2808, 2796, 2796, 2796, 2802, 2802, 2802, 2796, 2802, 2802, 2808, 2796, 2796, 2808, 2796, 2808, 2808, 2802, 2808, 2796, 2802, 2802, 2796, 2808, 2796, 2802, 2802, 2796, 2802, 2808, 2802, 2802, 2796, 2802, 2802, 2808, 2808, 2802, 2796, 2796, 2796, 2790, 2802, 2796, 2796, 2796, 2796, 2808, 2802, 2796, 2802, 2802, 2796, 2802, 2802, 2808, 2802, 2802, 2808, 2802, 2808, 2796, 2808, 2802, 2802, 2808, 2796, 2802, 2802, 2802, 2796, 2802, 2808, 2796, 2802, 2802, 2802, 2802, 2808, 2808, 2796, 2796, 2802, 2802, 2808, 2802, 2796, 2808, 2802, 2802, 2796, 2802, 2802, 2808, 2808, 2802, 2802, 2802, 2802, 2802, 2802, 2802, 2808, 2808, 2796, 2790, 2802]
Number of samples received: 122
Samples values: [2802, 2808, 2802, 2796, 2808, 2796, 2796, 2802, 2796, 2808, 2802, 2802, 2802, 2802, 2802, 2802, 2796, 2784, 2778, 2802, 2808, 2802, 2796, 2814, 2796, 2802, 2808, 2802, 2808, 2802, 2802, 2802, 2802, 2808, 2796, 2844, 2808, 2796, 2838, 2808, 2802, 2802, 2796, 2796, 2802, 2796, 2802, 2808, 2796, 2808, 2796, 2802, 2808, 2802, 2796, 2808, 2802, 2808, 2790, 2802, 2802, 2808, 2790, 2802, 2826, 2802, 2802, 2802, 2808, 2808, 2802, 2802, 2802, 2802, 2802, 2802, 2808, 2796, 2796, 2802, 2802, 2796, 2808, 2802, 2790, 2802, 2808, 2802, 2802, 2802, 2802, 2808, 2796, 2802, 2802, 2796, 2796, 2802, 2802, 2802, 2808, 2808, 2802, 2802, 2796, 2802, 2802, 2802, 2802, 2802, 2808, 2802, 2802, 2802, 2796, 2808, 2802, 2808, 2802, 2808, 2802, 2796]
Number of samples received: 122

Best regards,

Vidar

Time-sensitive: BLE packet size limited to 64 bytes even though MTU size negotiated to 244 bytes

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