nRF52840 fails to connect over USB

[Robert Lasater]

I have an nRF52840 board that fails to connect to Linux over USB.  The board powers on and the green LED at the lower left of the PCA10056 flashes on/off rather quickly.  But no new tty device appears and attempts to program the flash memory with nrfjprog fail.

I have reproduced this on Linux Mint 18 and Raspberry PI 4.19.97-v7l+ #1294.  A separate nRF52840 works without problem in the same setups.

My questions are, can a bad firmware build lead to this?  And is there anything I can do to recover this board?  Right now it appears to be a brick.

Thanks,

Robert Lasater

[Simonr]

Sorry, I forgot to include the link in my previous reply, I have edited the reply to include it now. 

Your DK is connected to the computer by a USB connector, right? If you hold the IF BOOT/RESET button while powering the DK on, the device should go to bootloader mode and a bootloader window should appear similar to the picture below. If you drag the Interface MCU firmware file into this Bootloader folder (and nothing else, as that may damage the Interface MCU) the device should recover to its original state.

Best regards,

Simon

[Robert Lasater]

Thanks for clarifying your original answer.  I'll give it a try and let you know what happens.

[Robert Lasater]

First, regret the delay in responding.  The 3-day weekend came quicker than I expected.

I have good news: your fix worked.

For some reason, that board quit coming up, and I could not get it to present a new File Explorer window on my Linux PC.  But to my surprise, this morning, the board came up without incident.

It has been a bit flakey in the past ...

Thanks for your help.