SDK 14.2: Slow directed advertising doesn't work

[Jacob]

I'm having issues with slow directed advertising. I'm having a BLE peripheral where I want the device to advertise (direct) upon disconnects. I initialize the advertising module as follows:

    init.config.ble_adv_fast_enabled            = true;
    init.config.ble_adv_fast_interval           = APP_ADV_INTERVAL;
    init.config.ble_adv_fast_timeout            = APP_ADV_TIMEOUT_IN_SECONDS;
    init.config.ble_adv_directed_enabled        = true;
    init.config.ble_adv_directed_slow_enabled   = true;
    init.config.ble_adv_directed_slow_interval  = 40;
    init.config.ble_adv_directed_slow_timeout   = 10;

When I disconnect my central (I have tried with both macOS and Android) I am able to connect I am really quick - hence regular (one-off) directed advertising seems to work, but if I wait until the slow directed advertising starts, I never manage to connect to it from the central. Once it times out and goes to regular fast advertising it works (my long-term goal is to disable the regular advertising to get a reconnect-to-last-device behavior).

I have an event handler registered and answers BLE_ADV_EVT_PEER_ADDR_REQUEST as expected (otherwise the one-off directed advertising wouldn't work, right?). I have added checks in ble_advertising.c and there is no error code returned by sd_ble_gap_adv_start. I get a BLE_ADV_EVT_DIRECTED_SLOW event.

Thanks, Jacob

[Mttrinh]

Hi,

What do you use on macOS and Android to connect to your device? nRF Connect? Do you get any errors on Central when trying to connect?

[Jacob]

Hello,

on macOS I'm using the Audio MIDI Setup (the device is a BLE MIDI device), on Android I'm using nRF Connect. No errors as far as I can see.

Thanks.

[Mttrinh]

Have you tried increasing these parameters?

init.config.ble_adv_directed_slow_interval 
init.config.ble_adv_directed_slow_timeout

According to ble_advertisement.h, ble_adv_directed_slow_timeout is number of tries. So your device will only do slow directed advertising in 400ms before it times out.

typedef struct
{
    bool     ble_adv_on_disconnect_disabled;  /**< Enable or disable automatic return to advertising upon disconnecting.*/
    bool     ble_adv_whitelist_enabled;       /**< Enable or disable use of the whitelist. */
    bool     ble_adv_directed_enabled;        /**< Enable or disable direct advertising mode. */
    bool     ble_adv_directed_slow_enabled;   /**< Enable or disable direct advertising mode. */
    bool     ble_adv_fast_enabled;            /**< Enable or disable fast advertising mode. */
    bool     ble_adv_slow_enabled;            /**< Enable or disable slow advertising mode. */
    uint32_t ble_adv_directed_slow_interval;  /**< Advertising interval for directed advertising. */
    uint32_t ble_adv_directed_slow_timeout;   /**< Time-out (number of tries) for direct advertising. */
    uint32_t ble_adv_fast_interval;           /**< Advertising interval for fast advertising. */
    uint32_t ble_adv_fast_timeout;            /**< Time-out (in seconds) for fast advertising. */
    uint32_t ble_adv_slow_interval;           /**< Advertising interval for slow advertising. */
    uint32_t ble_adv_slow_timeout;            /**< Time-out (in seconds) for slow advertising. */
} ble_adv_modes_config_t;

 

[Jacob]

Yes, I have tried changing the numbers up and down, and during slow (directed) advertising the device won't show up on the central side. It works on directed and fast advertising.

[Mttrinh]

Hi, 

Which example application are you using? Can you try using one of the HID examples, to see if that changes anything?