Upload program to nRF52840 via nRF52840-DK as J-Link

[Vint1k]

Hello.

I encountered the following problem. I have an nRF52840 microcontroller that is already soldered onto the PCB board. It doesn't have any bootloader.
As an example, I created a simple program in the nRF5 SDK (SES) that flashes an LED:

If I want to write this code to the nRF52840-DK - I just connect the DK via USB, then click "Build and run" - and it works. But I don't understand what I need to do to write the same code on my PCB board (not DK). On my PCB I have a SWD interface and a USB output, here is a photo:

I soldered the wires to the SWD and then connected them to the DK. It's exactly like the picture below, except VDD. Instead, I connected the PCB itself via USB too, so that there was power.


After that I connected the DK to the computer via USB. I launched J-Flash, selected "Create a new project", indicated the board type "Noridc-Semi nrf52840" and selected the .hex file of my project (from the folder "ses\Output\Debug\Exe\"), pressed the F4 and F5 buttons - and it wrote “Target programmed successfully”, but nothing happened. The LED built into the PCB did not start blinking.

Hence my questions:
1) Please tell me how to use nRF52840-DK as a programmer, like J-Link? There may be some instructions that I haven't found.
2) How can I be sure that I have connected the SWD interface pins correctly? On a regular J-Link, the green LED should be lit, indicating that the device is connected via SWD. I read this somewhere, but I could be wrong...
Is there something similar in the nRF52840-DK? Or can I somehow see on the computer that I have a device connected via SWD?
3) Is this the correct sequence to load the program I need onto my PCB? I mean through a .hex file. Or should we do something differently?

Thank you in advance for your answers.

[JONATHAN LL]

The image you have is a bit outdated as it shows the old nRF52DK, but in theory it is still the same. 



Make sure that you have nRF_VDD and VTG shorted and connected to the external board. From your image it does not loook like you have power connected correctly. 

2) How can I be sure that I have connected the SWD interface pins correctly? On a regular J-Link, the green LED should be lit, indicating that the device is connected via SWD. I read this somewhere, but I could be wrong...
Is there something similar in the nRF52840-DK? Or can I somehow see on the computer that I have a device connected via SWD?

There is no way to know, the DK does not indicate what SoC has been programmed visually on the kit it self. 

If you are using the nRF connect for Desktop Programmer app when connecting to the device then you can first wipe\erase (or flash a known app on there, like all LEDs on, if you want a visual indicator ) the DK so that it is blank. It will then show up as empty or will show the app that is loaded on there. When you then connect an external SoC to it it will show up as that and you can see whats loaded on there. If it differs from that of the known app you have on the DK then you know it is connected to the external one. 

3) Is this the correct sequence to load the program I need onto my PCB? I mean through a .hex file. Or should we do something differently?

Same thing as for the DK or any other device if there is no bootloader. You can use the Programmer app, nRFUtil, nRFjprog or whatever interface the IDE that you are using uses. SES or VSCode.


Regards,
Jonathan