https://devzone.nordicsemi.com/f/nordic-q-a/20387/gzp-gazell-pairing-library-causes-application-to-reset-into-bootloaderHello there, thanks so much for taking the time to read. My problem is the following I am trying to run GZP (Gazell Pairing Library). After successfully pairing with a Gazell Host, if I power cycle my Gazelle device (NRF52) after this point, it resetsen-USTelligent Community 13Mon, 13 Mar 2017 12:39:51 GMThttps://devzone.nordicsemi.com/thread/79478?ContentTypeID=1Mon, 13 Mar 2017 12:39:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2cef54d0-5f9c-4b3d-abcc-33f74f778761Hung Bui<p>Hi Alex,</p> <p>How big is your actual application size after you compile it ?</p> <p>It&#39;s maybe not a very good idea to write your data at address 0x50000 because it can be erased by the bootloader to get space for the swap bank to receive new image as shown <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v12.2.0/lib_bootloader_dfu_banks.html?cp=4_0_1_3_5_1_2_0_1#lib_bootloader_dfu_dual_banks_app">here</a>.</p> <p>But it&#39;s still quite strange that the bootloader is started after you modify flash at address 0x50000. The bootloader only calculate CRC of the application code base on the size of the application not outside it. 0x50000 should be outside.</p> <p>My suggestion is to debug function nrf_dfu_app_is_valid() in nrf_dfu_utils.c in the bootloader, either by printing log out or by adding a breakpoint and step into the code. You can find if the app valid function return true or not, and why. You can debug the bootloader as you do with a normal application.</p><div style="clear:both;"></div>