How to set BLE connection event length extension?

[ReedLi]

Hi everyone!

I'm working at ble multilink throughput, and the basic info shows as follows.

    chip: nRF52832(one central and eight peripherals)

    sdk: nRF5 SDK v17.0.2

    softdevice: s132 v7.0.1

    central example:  https://github.com/NordicPlayground/nrf52-ble-app-uart-c-multilink

    peripheral example: ble_app_uart

I konw connection event length greately affect the throughput.Now i have two questions about connection event extension.

1. In sdk_config.h, if central and peripherals have different NRF_SDH_BLE_GAP_EVENT_LENGTH setting, what's the actual connection event length?
2. If i want to extend connection event, do central and peripherals all need to use sd_ble_opt_set(BLE_COMMON_OPT_CONN_EVT_EXT, &opt) to enable the extension？

[Amanda Hsieh]

Hi, 

1. When adjusting the define NRF_SDH_BLE_GAP_EVENT_LENGTH, you will extend the amount of data that the peripheral can send, but this might still be restricted by the central side. 

2. Yes. You could use this conn_evt_len_ext_set function

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() in main() to enable extended BLE connection events.

Regards,
Amanda

[ReedLi]

Hi,

1. For example, if i want to set connect event length 7.5ms, should central and peripherals all set NRF_SDH_BLE_GAP_EVENT_LENGTH 6？

2.  If central and peripheral all need to call conn_evt_len_ext_set() to allow extend connect event length.

[Amanda Hsieh]

Hi, 

1. Yes, NRF_SDH_BLE_GAP_EVENT_LENGTH is the time set aside for this connection on every connection interval in 1.25 ms units. 6x1.25ms=7.5ms

2. Yes. 

-Amanda