https://devzone.nordicsemi.com/f/nordic-q-a/4400/dfu-bootloader-for-nrf51-evaluation-kit-suspected-bug-in-getting-bootloader-settingsDownloaded an used the latest (2 months old) code from DFU-Bootloader-for-nRF51-Evaluation-Kit After it didn&#39;t work out the gate, I&#39;ve attempted to narrow down and root cause reasoning. Seems the code initializes fine, but the function: bootloader_app_is_validen-USTelligent Community 13Tue, 11 Nov 2014 12:25:28 GMThttps://devzone.nordicsemi.com/thread/15635?ContentTypeID=1Tue, 11 Nov 2014 12:25:28 GMT137ad170-7792-4731-bb38-c0d22fbe4515:bfcb4775-852f-4ac9-ac65-6e416bea0102Stefan Birnir Sverrisson<p>Hi</p> <p>According to the SDK <a href="http://developer.nordicsemi.com/nRF51_SDK/doc/7.0.1/release_notes.txt">release note</a>s, nRF51 SDK v6.0.0 is only compatible with version 7.0.0 of the S110 softdevice, so try to use v7.0.0 instead. The bootloader you are using is based on nRF51 SDK 6.0.0 bootloader.</p><div style="clear:both;"></div>