Sending multiple packets at every interrupt interval

[yokokawa]

OS in development environment ：Windows7
HARD :(Taiyo Yuden)EBSHSN Series Evaluation Board : Central / Peripherals
CPU :(Nordic) nRF52832 / ARMR Cortex-M4F 32 bit processor 28-pin Land Grid Array / 15GPIOs / SWD
Soft Ver:nRF5_SDK_15.3.0_59ac345
Sample program used: "ble_app_uart" / "ble_app_uart_c"

In the sample program, one packet (244 bytes) is transmitted at each connection interval.
How can I send multiple packets at every connection interval?

Setting:
#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(30, UNIT_1_25_MS) /**< Maximum acceptable connection interval (75 ms), Connection interval uses 1.25 ms units. */
#define NRF_SDH_BLE_GAP_DATA_LENGTH 251
#define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 247

Thanks for your cooperation.

[Sigurd]

Hi,

You should increase NRF_SDH_BLE_GAP_EVENT_LENGTH in sdk_config.h, set it to e.g. 50.

You might also want to enable extended BLE connection events.

    ret_code_t err_code;
    ble_opt_t  opt;

    memset(&opt, 0x00, sizeof(opt));
    opt.common_opt.conn_evt_ext.enable = 1;

    err_code = sd_ble_opt_set(BLE_COMMON_OPT_CONN_EVT_EXT, &opt);
    APP_ERROR_CHECK(err_code);

[yokokawa]

1)Should NRF_SDH_BLE_GAP_EVENT_LENGTH be set to 50 in sdk_config.h for both "ble_app_uart" and "ble_app_uart_c"?
2)Where can I add a program that enables extended BLE connection events?
Thanking you in advance.

[Sigurd]

1) Yes.

2) Create a function like this:

void conn_evt_len_ext_set(void)
{
    ret_code_t err_code;
    ble_opt_t  opt;

    memset(&opt, 0x00, sizeof(opt));
    opt.common_opt.conn_evt_ext.enable = 1;

    err_code = sd_ble_opt_set(BLE_COMMON_OPT_CONN_EVT_EXT, &opt);
    APP_ERROR_CHECK(err_code);
}

and call it after ble_stack_init(), snippet:

int main(void)
{
    bool erase_bonds;

    // Initialize.
    uart_init();
    log_init();
    timers_init();
    buttons_leds_init(&erase_bonds);
    power_management_init();
    ble_stack_init();
    conn_evt_len_ext_set();
    gap_params_init();

[yokokawa]

1)How can I calculate the value set for NRF_SDH_BLE_GAP_EVENT_LENGTH?
2)Is the program that enables the extended BLE connection event added to both "ble_app_uart" and "ble_app_uart_c"?
Thanking you in advance.

[Sigurd]

1) Set it to match the max connection interval for your application.

Note that it's also possible to manually increase the TX buffer, e.g.

    ble_cfg_t ble_cfg;
    memset(&ble_cfg, 0, sizeof ble_cfg);
    ble_cfg.conn_cfg.conn_cfg_tag           = APP_BLE_CONN_CFG_TAG;
    ble_cfg.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = 50;
    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_cfg, ram_start);
    APP_ERROR_CHECK(err_code);

(should be added to ble_stack_init() in main.c )

2) Yes.

If you want to see the on-air traffic, you should check out the nRF Sniffer.