https://devzone.nordicsemi.com/f/nordic-q-a/9088/characteristic-writeHow to add characteristic write only in peripheral server and how to know the char was writeen-USTelligent Community 13Mon, 07 Sep 2015 12:10:15 GMThttps://devzone.nordicsemi.com/thread/33452?ContentTypeID=1Mon, 07 Sep 2015 12:10:15 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6aa781ce-17c3-4c48-b105-88081c97e640MartinBL<p>Hi. I&#39;m not sure if I quite understand what you mean. If you want to apply &quot;write-only&quot; permissions to your characteristic you can set the relevant bits in the <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s110.api.v8.0.0/structble__gatt__char__props__t.html?resultof=%22%62%6c%65%5f%67%61%74%74%5f%63%68%61%72%5f%70%72%6f%70%73%5f%74%22%20">GATT Characteristic Properties</a> before you call <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk51.v9.0.0/ble_serialization_s110_functions_gatts.html?resultof=%22%73%64%5f%62%6c%65%5f%67%61%74%74%73%5f%63%68%61%72%61%63%74%65%72%69%73%74%69%63%5f%61%64%64%22%20">sd_ble_gatts_characteristic_add()</a>. Have a look at the examples in our SDKs.</p> <p>When your characteristic is written to you will get a <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s110.api.v8.0.0/group___b_l_e___g_a_t_t_s___e_n_u_m_e_r_a_t_i_o_n_s.html#ggae537647902af1b05c1e32f12d6b401c7aa68b7764f5264ff092d2ad17851355ed">BLE_GATTS_EVT_WRITE</a> event from the Softdevice with <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s110.api.v8.0.0/structble__gatts__evt__write__t.html?resultof=%22%62%6c%65%5f%67%61%74%74%73%5f%65%76%74%5f%77%72%69%74%65%5f%74%22%20">this data</a>.</p><div style="clear:both;"></div>