https://devzone.nordicsemi.com/f/nordic-q-a/18382/failed-to-perform-ota-dfu-using-nrf-toolbox-dfu-4-2-for-sdk11-sdk10I am using IOS nRF Toolbox 4.2 DFU function on nRF51 DK PCA10028. I followed the tutorial here . Use nRFgo Studio to erase all. Use nRFgo Studio to program softdevice s130_nrf51_2.0.0_softdevice.hex (SDK11) s130_nrf51_1.0.0_softdeviceen-USTelligent Community 13Thu, 15 Dec 2016 08:53:32 GMThttps://devzone.nordicsemi.com/thread/70958?ContentTypeID=1Thu, 15 Dec 2016 08:53:32 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6d4dbf54-6395-46a5-943a-038eb6947adebjorn-spockeli<p>Could you try to generate your own zip by compiling the hrm example with DFU support and generating a zip with the hex using nrfutil?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/70959?ContentTypeID=1Wed, 14 Dec 2016 19:27:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0207d651-70de-423d-9be0-65cd45ca0269daniel77<p>No progress bar. Just a half second of &quot;starting Dfu&quot; message and it exits immediately after I press upload. I have tested SDK12.1/12.2 DFU bootloader with same method and they are fine. I was wondering any change of nRF Toolbox requires the old SDK .zip to be updated, perhaps to include some additional info. I was thinking of going back to previous SDK since buttonless DFU may seem more stable. I am still attempting to get the SDK 12.2 buttonless DFU to work.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/70957?ContentTypeID=1Wed, 14 Dec 2016 13:25:42 GMT137ad170-7792-4731-bb38-c0d22fbe4515:38259946-e9df-4b5a-b05f-492c35764b5cbjorn-spockeli<p>This should not be an issue since nRF Toolbox v4.2.0 is compatible with both Legacy and Secure DFU. When the DFU process starts, do you see a progress bar or does the DFU fail immediately after you press upload?</p><div style="clear:both;"></div>