I have a PCA10056 (nrf52840 DK) and a couple PCA10059's (nrf52840 Dongle).
I'm trying to get the DK to have the same/similar DFU as the dongles.
My development machine is a linux system running ubuntu 18.04 LTS
What I did, using the nRF5_SDK_for_Thread_and_Zigbee_2.0.0_29775ac SDK:
USB cable plugged into J-Link USB port (J2):
LED2 is now pulsing on and off, indicating that its in DFU mode.
Move USB cable to the nRF USB connector:
nrfutil pkg generate --debug-mode --hw-version 52 --sd-req 0x00 --application _build/nrf52840_xxaa.hex dfu.zip
nrfutil dfu usb-serial -pkg dfu.zip -p /dev/ttyUSB0 -b 115200
and the blinky program runs. If I hit reset it goes into the bootloader, but if I power cyclce it also goes into the bootloader and doesn't run blinky.
If I build blinky for the PCA10059 and flash using the same commands as above, then it runs blinky at poweron and at reset it runs the DFU.
What else do I need to do to make the DK behave like the Dongle? I know that the Dongle has the reset line hooked upto some GPIO pins, but I thought that this was just for the DFU trigger library?
I'm planning on use the 52840 for a zigbee application and do not need the soft device.
Not sure what this means, but if I power the DK using the J-Link USB port then it runs the blinky app, whereas if I power it via the nRF USB connector it starts the DFU bootloader.
Most likely the reset button (SW5) is not powered by the VDD_USB, leaving the RESET pin floating. This could cause a reset and the bootloader to see this as the button being pushed.
Can you try pulling the reset pin high while powering through NRF_USB?
Indeed, that does seem to be the problem. If I put a 10K resistor between P0.18 (on P24) and VDD_NRF (on P20) then it works as expected when powering through NRF_USB. Looking at the schematics, I suspect that populating R54 will achieve the same result.