https://devzone.nordicsemi.com/f/nordic-q-a/35279/question-about-indication-charactristicHi to all, I am new i ble tech, i read some where that notification charactristic dose not need acknowledgement but indication need, now i want know that this acknowledgement must be sent by ble stack or user application?? Thanksen-USTelligent Community 13Mon, 11 Jun 2018 09:16:44 GMThttps://devzone.nordicsemi.com/thread/135520?ContentTypeID=1Mon, 11 Jun 2018 09:16:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b62cee32-5ba2-4630-9b36-ac828737ceb7Sigurd<p><em>Hi,</em></p> <p><em>Indications</em> require an explicit acknowledgment <strong>from the client</strong> in the form of a <em>confirmation</em>. A smartphone or a tablet is typically the client/central, while the nRF5 is the server/ peripheral.</p> <p>If the nRF5 is the server, you will get an event BLE_GATTS_EVT_HVC when the client confirms. See <a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v6.0.0/group___b_l_e___g_a_t_t_s___h_v_i___m_s_c.html?cp=2_3_1_1_0_2_4_3_2">this message sequence chart</a>. After you get the confirmation/event, you can send another indication to the client. Again, it is the client that sends the&nbsp;<span>acknowledgment, not the server.</span></p> <p>If you are running the nRF5 in the client/central role, the nRF5 must do the confirmation. This must be done by the user application, by using the function&nbsp;sd_ble_gattc_hv_confirm(). See <a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v6.0.0/group___b_l_e___g_a_t_t_c___h_v_i___m_s_c.html?cp=2_3_1_1_0_2_2_3_8">this message sequence chart</a>.</p><div style="clear:both;"></div>