https://devzone.nordicsemi.com/f/nordic-q-a/89020/write-long-characteristicsTeam, I am using nrf52810, sdk 17, sd112. I have setup a write characteristics, to receive some long data ( 64 bytes) // write char memset(&amp;add_char_params, 0, sizeof(add_char_params)); add_char_params.uuid = LBS_UUID_WR_CHAR; add_char_paramsen-USTelligent Community 13Thu, 16 Jun 2022 11:53:51 GMThttps://devzone.nordicsemi.com/thread/372794?ContentTypeID=1Thu, 16 Jun 2022 11:53:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:7eec0cba-f5b0-4c06-9ab3-e0df6ca08381Simonr<p>Hi</p> <p>1. Are you sure the nRF52810 application is set up to support higher MTU sizes than 23 bytes (which is the standard non-extended maximum size).<a href="https://www.novelbits.io/bluetooth-5-speed-maximum-throughput/"> This blog post</a> has a great explanation on how to increase throughput and how to set up larger MTU sizes for nRF devices.</p> <p>2. <a href="https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.s140.api.v7.0.1%2Fgroup___b_l_e___c_o_m_m_o_n___f_u_n_c_t_i_o_n_s.html&amp;anchor=ga6d49592ed6722290fee71419be7dac1f">sd_ble_user_mem_reply </a><span>is used to provide a user memory block, and can only be used as a response to a BLE_EVT_USER_MEM_REQUEST event.</span></p> <p>3. If you&#39;re working with an Android device and the nRF Connect for Android app you should be able to set other MTU sizes from the ... menu next to the name of the connected device, which is what should initiate an MTU exchange once connected. It&#39;s also possible to set this up on the peripheral side if you want, but the central device will have to support the suggested value to &quot;allow&quot; it. There is usually an MTU exchange right after devices have connected to one another to find values they both support.</p> <p>Best regards,</p> <p>Simon</p><div style="clear:both;"></div>