https://devzone.nordicsemi.com/f/nordic-q-a/11810/bootloader-and-application-both-running-at-the-same-timeHello, I want to import DFU bootloader to my project. Now i got DFU working with &quot;hrm&quot; example. I can upload .zip file to my nRF and everything works perfect. When i want to upload with DFU .zip file with my apllication, module (nRF) doesn&#39;t advertiseen-USTelligent Community 13Wed, 10 Feb 2016 10:13:41 GMThttps://devzone.nordicsemi.com/thread/44658?ContentTypeID=1Wed, 10 Feb 2016 10:13:41 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9205016d-e805-43c7-ac64-2ef36ec4fd88nejcokle<p>Nevermind, i checked again if there is a problem with my app, and it didn&#39;t seem to be working properly. I don&#39;t know why is that, since i didn&#39;t change anything, but luckily i had backup. Everything works great now.</p> <p>Thanks for your help. Best regards, Nejc</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/44657?ContentTypeID=1Wed, 10 Feb 2016 07:25:54 GMT137ad170-7792-4731-bb38-c0d22fbe4515:414dc68b-1982-4cf0-ad42-4c521bee85f7Vidar Berg<p>Hello,</p> <p>The bootloader will always be executed first on startup (<a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.130.sds.v1.0.0/mbr_bootloader/mbr_sd_reset_behavior.html?cp=2_7_2_0_9_2">reset behavior</a>), and it will determine whether it should go into DFU mode, or forward execution to the application given that it&#39;s valid.</p> <p>When doing DFU of application the bootloader will mark the application as valid once finished by setting a flag in bootloader settings, othwerwise the bootlaoder will fall back into DFU mode.</p> <p>In your case it sounds like there may be problem with the application itself. Assume it doesn&#39;t advertise if your are loading it directly through the SWD interface either? Have you tried to attach a debugger and see if the application is asserting or hanging somewhere in the code?</p><div style="clear:both;"></div>