Difference in reset between nRF52840DK and dongle?

[Fredcoach]

Hello,

I made my nRF52840DK go to sleep.

It was immediately restarting.

RESETREAS and LATCH gave me the cause of the reset and I fixed it.

Now, I can put it to sleep, it does not restart without reason.

Then I ported the exact same code to the dongle (only adjusting the IO addresses).

Nothing is connected to the dongle IO ports, I even disconnected the UARTs used on the nRF52840DK.

It keeps restarting and RESETREAS has no bit set.

I am now short of new ideas.

Do you know what is different? And how to make it work?

Thanks,

Frederic

[Turbo J]

Maybe the bootloader on the dongle kills RESETREAS bits in order to be able to properly run when called by the application?

[Fredcoach]

Is the bootloader different in  nRF52840DK and the dongle?

I loaded the same softdevice and the bootloader is supposed to be included in it...

To be completely sure, I just reflashed the softdevice and the problem is still there.

[Turbo J]

The Dongle has an USB bootloader, the DK has a JLink that talks directly to the NRF chip via SWD.

Without the USB bootloader you would need to connect a debugger via SWDIO an SWDCLK to the dongle in order to program the device.

And yes, the bootloader runs at every Reset before the application even starts.

[awneil]

Fredcoach said:

To be completely sure, I just reflashed the softdevice

To be completely sure, you should do a full chip erase first.

[Fredcoach]

I also flash the DK using the USB.

But there should not be any reset at all, thus the bootlader should not have to run. 

[Fredcoach]

Ok, I'll also try this, thanks.

[awneil]

Fredcoach said:

I also flash the DK using the USB

There are two "USBs" on the nRF52840DK 

• one for the on-board J-Link
  https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/nrf52840_DK/if_mcu.html?cp=3_0_4_6
   
• one for the nRF52840's own USB
  

[Fredcoach]

It is used to flash the device, provides a virtual COM port and is seen externally as a disk drive. Thus it should be the on-board J-Link. And we do not program any USB device.