nRF52840DK stopped connecting in intermediate course lesson 8 exercise 2

[craig.goldman]

I was working through Nordic Intermediate course lesson 8 exercise 2 - DFU over USB, adding external flash and custom keys.
I was using an nRF5280DK.  (Sticker: PCA10056 2.0.1 2020.33) and my PC running Windows 10.
All work was done using Visual Studio Code.

I got through all the parts of step#7 where the firmware is downloaded using the nRF USB port on the DK.   All went well; firmware downloaded and executed correctly - LED1 blinking appropriately.

During step#8, the PC is connected again to the DK debug port; but Visual Studio Code shows no devices connected.
The DK is powered and blinking LED1 shows it is running the last code downloaded by the bootloader using the USB.
The PC Device Manager also shows no COM Ports on the PC USB.

What happened? Can this be fixed? Have I bricked the DK following the lesson8 instructions?

-Craig Goldman

[Menon]

Hello,

I'm not entirely sure, but the issue might be due to the onboard debugger being compromised during the DFU process. If you have another DK, you can try using it as an external debugger to access the non-working board. Connect the Debug Out (P19) of the DKs to each other using a 10-pin Serial Wire Debug (SWD) cable.

Kind Regards,

Abhijith

[craig.goldman]

I do not have a 10-pin serial cable with the small female connector which can plug into P19. Do you know if Digikey or someone else sells this type of cable?

If I acquire the cable, does the other end plug into P18 of the "bad" board?

Once the two boards are connected, is there a way to re-program the onboard debugger?  Is there something else which should be done? Is there documentation on this entire process?

[Menon]

Hello,

I’m not sure what happened here. Just to confirm, I followed the DevAcademy steps and completed the DFU via USB. When I reconnected the debug ports, I was able to see the device in VSCode and the Device Manager (as JLink). Can you communicate with your DK via nRF USB using mcumgr? If so, try uploading a different binary file to the DK and see if that works.

Could you also check what happens if you hold the IF BOOT/RESET button while powering the DK off and back on using the power switch (SW8)? Does it show up as BOOTLOADER on your computer?

If it does show up as BOOTLOADER, try pasting the Interface MCU firmware (JLink-OB-SAM3U128-V2-NordicSemi 170724.bin) that you can download from here. After a few seconds, power cycle the DK without holding IF BOOT/RESET and see if it works now. Please note that if you have a newer version of the DK (this can be identified on the white sticker), this method might not work. Let me know if it works or not

craig.goldman said:

I do not have a 10-pin serial cable with the small female connector which can plug into P19. Do you know if Digikey or someone else sells this type of cable?

I don’t have a specific website recommendation for purchasing it.  (see the screenshot, for reference)

craig.goldman said:

If I acquire the cable, does the other end plug into P18 of the "bad" board?

Yes, please check the Debug Out and Debug In connections.

Kind Regards,

Abhijith

[craig.goldman]

I tried connecting to debug USB and holding reset while enabling power using switch. The PC no longer recognizes a serial port attached to the debug USB so I can't tell if BOOTLOADER sends any text.

I can download new code via nRF USB using mcumgr.
The board is not dead, but there is no communications through the normal debug USB.

I tried activating J-Link Commmand V7.96J while connecting to debug USB.  It said "No probes connected via USB."  No emulator was found using TCP/IP.

The cable in the picture has standard JTAG "Berg" connectors with socket spacing 0.1"x0.1".  I have several of these cables.  The10-pin "Debug Out" and "Debug In" on the nRF52840 DK has a smaller connector (I do not know type) with pin spacing of ~1.27mm by ~1.27mm.  I would like to purchase a compatible cable but do not know where.

-Craig Goldman