Cannot connect nRF52840DK to PC anymore

[RF_Eng]

I have two nRF52840DK boards that I was working with recently.

PCA10056
3.0.2
2024.33

I flashed one board with a BLE peripheral device code from the nRF connect sample projects. The problem is that for one board, I cannot connect to it through my PC anymore, while the other one works fine.

I am using the IMCU USB port to connect it to the PC, SW9 is set to VDD, SW6 to Default, Vext is set to off, flow control is on. Checking the device manager, there is no change when I connect it. Interestingly the BLE firmware is running correctly since I can see the device when I open the bluetooth interface from my phone, but I am unable to reflash or connect it to the PC.

Holding the reset button, while restarting the board also doesn't help.

Trying nrfutil device recover, returns the error
Error: No devices with requested serial number(s) or trait(s) found

Interestingly, turning on the board without a micro usb cable connected and with the SW9 set to VDD, would make the BLE firmware run and the LEDs are blinking and operating normal.

Switching SW9 to USB, leads to the LEDs 1-4 to blink quickly and faintly, but no more changes. The same setup on the other board work fine and I am able to connect it to the PC. I am not sure what went wrong or how to fix it, could you please help me how to re-establish the connection to the PC again?

[Priyanka]

Hi,

This could be that the interface MCU has become faulty.
What do you get when you try this?

Holding the reset button, while restarting the board also doesn't help.

Did you try nrfjprog device recover? PLease install the nRF Command Line Tools and try this.

Could you try to open the Programmer app in the nRF Connect for Desktop application, and see if you are prompted to re-program the debug chip?

-Priyanka

[RF_Eng]

Hi Priyanka,

Nothing happens when I hold the reset button and restart the board.

As far as I saw on the website, nrfjprog are archived, so I tried the alternative nrfutil, but this didn't detect the board.

Starting the programmer tool also didn't detect the device and didn't prompt re-programming.

I am not sure what could have happened to the board, as I just recently bought it and didn't try anything except some of the basic applications and always programming using visual studio code with the nrf plugin/extension. Is there a way to regain access to the board?

[Priyanka]

Hi,

Could you try connecting to the other USB on the board? This can help confirm if it's the debug chip's issue.

-Priyanka

[RF_Eng]

Thanks for the suggestion!
Sure, But what should I observe when I connect the other USB on the board?

[Priyanka]

WHat was the firmware that you flasehd onto the DK? If it uses a USB, then you should see a new USB device pop up on the PC (COM port). But if the firmware you flashed did not use USB, then you will still not see anything, but the BLE should work and the LED should work as usual.

-Priyanka

[RF_Eng]

I have flashed the BLE Uart Service (from the examples) without any modifications.
I connected the cable to USB J3, the BLE works and LED1 flash as usual, but still can't see the COM port on the PC. No changes in the device manager when I connect it.

[Priyanka]

Hi,

Then it should be an issue with the debugger. I will report this internally and will keep you updated.

-Priyanka

[RF_Eng]

Thanks a lot