nRF52840 Dongle restore bootloader

[piers]

It appears that the DFU bootloader has been overwritten/damaged on nRF52840 Dongle as it no longer resets (the red flashing led does not show) when I hit the RESET button. This happened when I was trying to use the Power Profiler app from the nRF Connect App (v3.6.1) on MacOS10.15.7 and after the point where it asks to reprogram the Dongle it got into this state. I had previously successfully tried the Bluetooth Low Energy app. I also tried the RSSI app but it wouldn't work (it tried to reprogram the dongle but failed to work but it did reset afterwards).

How can I reload the original DFU bootloader or restore it to its original state? I no longer see the device in /dev/ so unclear how to proceed? Do I need to a buy a 'DK' board to fix this or can it be done just with my laptop?

Thanks,

Piers

[Simonr]

Hi Piers

It should be very hard to accidentally erase the bootloader without having used the pin header and a J-Link/DK as a programmer.

But if you have indeed erased the bootloader you will need to use an external debugger (J-Link or DK) to recover the bootloader on the Dongle. Please check out our Dongle Programming tutorial for details as to how it can be recovered.

Best regards,

Simon

[piers]

Thanks for your reply. Unfortunately it seems that the device has been rendered inoperable when I just tried using the Power App from the nRF Connect app with the dongle connected via USB which is disappointing. 

I have since tried to connect to it using SWD via OpenOCD running on a Pi, but unfortunately I could not communicate with it which might to indicate that it suffered hardware failure/damage? I'm not sure if there's another way to check if the hardware is still functioning? I don't have a full array of debugging equipment - just a Pi 3B and a multimeter.

I guess the only other possibility is that it suffered from a static or shorting damage when I was handling it - should one be particularly careful with these dongles in that respect?

Thanks,

Piers