Hi,
As the title said, does the SD support?
If YES, how to switch between High Duty and Low Duty?
Thanks.
Take a look at ble_gap_adv_params_t in ble_gap.h. It explains what the interval should be if you are using BLE_GAP_CONN_MODE_DIRECTED The struct documentation also talks about setting p_peer_addr
You should get a BLE_GAP_EVT_TIMEOUT BLE_GAP_TIMEOUT_SRC_ADVERTISEMENT once your one second of directed advertisement is up. You should then decide what to do from there.
The template app is a good place to start as it has a fast undirected and slow undirected advert mode. You could easily add a directed advert mode into the chain.