https://devzone.nordicsemi.com/f/nordic-q-a/10656/after-press-the-upload-button-this-situation-appearsThe way of entering the bootloader mode is sending the command,then run the code as follows: void jump_to_bootloader(void) { uint8_t softdevice_enabled; uint32_t err_code; err_code = sd_softdevice_is_enabled(&amp;softdevice_enabled); if(softdevice_enableden-USTelligent Community 13Mon, 07 Dec 2015 14:22:40 GMThttps://devzone.nordicsemi.com/thread/39779?ContentTypeID=1Mon, 07 Dec 2015 14:22:40 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2d6a8b14-6c42-405e-9998-a5b7fbca1cacHung Bui<p>Hi Cheese, I saw that you GPREGRET to 0xA0 (set sd_power_gpregret_set(0xA0)) before reset to bootloader. I assume that you modified the bootloader a little bit ? What happens if you try with our bootloader ? and our ble_app_hrs_with_dfu app ? If you can capture a <a href="https://www.nordicsemi.com/eng/Products/Bluetooth-Smart-Bluetooth-low-energy/nRF-Sniffer/(language)/eng-GB">sniffer trace</a> when doing DFU it would be great.</p><div style="clear:both;"></div>