https://devzone.nordicsemi.com/f/nordic-q-a/62056/sdk12-1-nrf51822sdk12-1-nrf51822this is my code on DFU function, I copy to the example of experimental_ble_app_buttonless_dfu on SDK12.1. I used nrfgo studio to program s130_nrf51_2.0.1_softdevice , boot_setting.hex(used nrfutil to produce ), nrf51822_xxac_s130. and then my cellphoneen-USTelligent Community 13Wed, 03 Jun 2020 12:40:33 GMThttps://devzone.nordicsemi.com/thread/253003?ContentTypeID=1Wed, 03 Jun 2020 12:40:33 GMT137ad170-7792-4731-bb38-c0d22fbe4515:ab623bc1-e8da-4ea8-b99c-11b35f898028Vidar Berg<p>Hello,</p> <p>Unfortunately, I can&#39;t say what&#39;s wrong based on the code snippet you posted. It only shows the part where the buttonless service is initialized, and we know that part is working because it gets displayed in the mobile app.</p> <p>Please try to debug the FW running on the 51 and check if the ble_dfu_evt_handler() gets called when you attempt to start DFU from nRF connect.</p><div style="clear:both;"></div>