https://devzone.nordicsemi.com/f/nordic-q-a/15378/device-does-not-start-after-bootloader-softdevice-dfu[symptom] I want to update my application/bootloader/softdevice by DFU. Steps are shown below. bootloder/softdevice update. if 1 step is done, application update comes next. I wrote some code for iOS/Android apps based on IOS-Pods-DFUen-USTelligent Community 13Thu, 28 Jul 2016 09:00:31 GMThttps://devzone.nordicsemi.com/thread/58736?ContentTypeID=1Thu, 28 Jul 2016 09:00:31 GMT137ad170-7792-4731-bb38-c0d22fbe4515:457eaccb-cd37-4ff7-bc0b-f1f6535d8792Hung Bui<p>@shtsht: Please correct me if I am wrong. You meant you can update the bootloader and or softdevice , but the device doesn&#39;t start in bootloader mode after you update and it requires you to turn the device off an on with a button pressed ?</p> <p>Are you sure you managed to update the bootloader successfully ? Have you verified by for example change the device name in the advertising packet? Have you tested with updating the application ? When you update the application, would the new application start automatically ?</p> <p>Have you made sure the APP_VALID bit in the bootloader is not set by accident ? When there is no application , this bit should be set as INVALID_APP.</p> <p>You may consider to modify the bootloader so you can debug it after you update the bootloader. You can have a look at question F in this <a href="https://devzone.nordicsemi.com/blogs/685/common-faq-on-dfu/">FAQ</a>.</p><div style="clear:both;"></div>