nRF52840 Dongle Reset Issue

[makoto.inoue]

Hello,

I am having an issue where the nRF52840 dongle does not properly reset. I'd appreciate it anyone can help.

I was evaluating the DFU options, and erased the IC in the process. I am now trying to get it back to the default state. I used the J-Link debugger to flash the factory MBR, Bootloader (and changed the UICR to get 3.3v VDD out). I have two nRF52840 Dongles, one of the two does works fine (after going through the refresh process), and the other seems not. The one that is not working, actually does "work" when the J-Link debugger is attached.

When I attach the J-Link debugger, it does reset properly:

• I am able to reset via the nrfjprog.
• I am able to reset via the reset button.
• The dongle gets listed in nRF Connect Desktop App.
• Slow blinking red led is on.

When I do not attach the debugger:

• reset button does not seem to put the device in reset
• The dongle does not get listed in nRF Connect Desktop App.
• fast blinking red led is on.

Thanks,

Mak

[Simonr]

Hi

Can you walk me through how you tested for secure DFU OTA, so I can try to recreate the problem on my side? Please also refer to what firmware you used to flash it.

Best regards,

Simon

[makoto.inoue]

Hi,

Simonr said:

Can you walk me through how you tested for secure DFU OTA, so I can try to recreate the problem on my side?

It was couple months ago, so I am not sure on the exact steps I took. I should have kept a log...

After trying out the secure DFU OTA, I didn't touch it until about a week ago, and found out something was not working right.

With that said, I recall first trying the one with "debug purpose only" secure BLE DFU example. After confirming that it worked, I followed the instructions listed in ble_sdk_app_dfu_bootloader to create my own signed firmware to flash. I was able to create a custom private/public key pair, and use the nRF Connect App for smartphone to flash it.

Simonr said:

Please also refer to what firmware you used to flash it.

Unfortunately I must have deleted the firmware I signed with my private key, as I can't locate it. I think it was the sample *.hex files that I used created the *.zip ... 

Thanks,

Mak

[Simonr]

Hi

I can't seem to get a Dongle in the state yours is in. I did manage to get a fast blinking red LED, but I simply had to remove it from both debugger and USB port, then putting it back into the USB port to get it back to working normally.

I have however found a thread on the forum where someone with the nRF52832 DK had the same problem of the chip not working without the debugger. There are some tips here that could be worth testing on your Dongle as well. Please have a look, to see if anything helps. Starting to run short on ideas here.

Best of luck and kind regards,

Simon

[makoto.inoue]

Hi, 

Thanks for the suggestion. I read the thread - maybe some pins could be receiving power when it is not supposed to? I commented on the other response below, but I'm seeing a strange fluctuating GND value (reading from the edge GND pins), when the debugger is not connected. Any suggestion for why that could be the case? 

Thanks,

Mak