https://devzone.nordicsemi.com/f/nordic-q-a/54111/cannot-buttonless-dfu-on-nrf52840Hi, This is unrelated to my other open question. I have programmed the secure ble bootloader and can OTA flash the buttonless bootloader example . My problem is that when I try to perform a buttonless update, the device restarts back into theen-USTelligent Community 13Thu, 07 Nov 2019 14:32:58 GMThttps://devzone.nordicsemi.com/thread/219103?ContentTypeID=1Thu, 07 Nov 2019 14:32:58 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d86d460d-01c7-4e5e-9426-754d10505a4amredp<p>A new board arrived with the ISP-1807 module and this now works fine. For some reason it was not working on the previous module the BC840. Thanks for your help.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/219090?ContentTypeID=1Thu, 07 Nov 2019 14:15:18 GMT137ad170-7792-4731-bb38-c0d22fbe4515:11191172-b12f-4187-9c23-cc4718590b0dEinar Thorsrud<p>Hi,</p> <p>This mechanism is exactly the same on nRF52832 and nRF52840, so that itself should not be relevant.</p> <p>I recommend you flash the debug bootloader with RTT logging as the first step. The logging is quite extensive, and in many cases, you can read directly out of the log what has happened. If not, you can add more log output in the relevant region. The relevant part of the bootloader is where it reads the retention register, looking for&nbsp;BOOTLOADER_DFU_START (assuming a recent SDK) in&nbsp;dfu_enter_check() in nrf_bootlaoder.c. If that is not set at that point, then it is either cleared before it is read or never written in the first place.</p><div style="clear:both;"></div>