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

The interface MCU solution I was wrong about, sorry for the confusion (It works on the 51 Dongle). This could seem like a hardware issue indeed. They both worked initially before the UICR erase am I right? It seems to me like the one not working was damaged somehow during the soldering process of resetting it. Have you checked that any of the solder bridges haven't been damaged or some components haven't been shorted by soldering paste?

Best regards,

Simon

[makoto.inoue]

Hi,

Simonr said:

They both worked initially before the UICR erase am I right?

Yes. Initially they both worked. Only the one that I re-flashed to test different DFU mode (was testing secure DFU OTA actually) is no longer working. 

Simonr said:

Have you checked that any of the solder bridges haven't been damaged or some components haven't been shorted by soldering paste?

I have not made any modification physically to the dongle. To a naked eye it looks the same as the working one.

If I have the debugger connected, I can run the ble_app_blinky and debug (step it through) it after erasing the bootloader. If I flash the debug or release build on the dongle, it will work properly only if I have the debugger attached. It stops running when the debugger is removed.

Below is a summary of what I have tried with no boot loader, ble_app_blinky on the dongle.

• If the dongle is connected to the computer and debugger is connected, it will function properly.
• If the dongle is connected to the computer and debugger is not connected, it will not work.
• If the dongle is not connected to the computer, and debugger connected, it will not work (it is not receiving power from the debugger).
• If the dongle is connected to a USB power-only connection, and debugger connected, it will not work.  

Maybe there is some issues with D+ and/or D- lines or its related circuitry. Would that matter in normal application execution (if it does not require UART type serial data)? 

Thanks,

Mak

[hmolesworth]

Long shot .. are you using P1 or J2 to attach the debugger? If using P1, try with debugger removed and connect RESET P1 pin 10 to VDD_nRF P1 pin 1.

[makoto.inoue]

Hi,

Thanks for the suggestion. I am using J2 with the tag-connect in circuit cable.

I tried soldering P1 pin10 to P1 pin 1, but no luck (did I test it correctly? see below pic). I think that will pull up the reset - the suspicion here is that the reset is somehow constantly bing pulled down, that it is trying to trigger reset all the time?

Thanks,

Mak