Bricked nrf52840 Dongle

[bricked]

I thought I had been extremely careful to _not_ brick the device, but apparently I did.

I created a firmware-dfu.zip file, even with appropriate keys, etc. as below.

  if /nix/store/if9z6wmzmb07j63c02mvfkhn1mw1w5p4-systemd-257.5/bin/journalctl --dmesg -b | grep -q 'Open DFU Bootloader'; then
    echo "dmesg detected a device with an Open DFU Bootloader" &&
    if /nix/store/zd7fljlfxbf071lpbr0kkfxhfw35ljzi-usbutils-018/bin/lsusb | /nix/store/gqmr3gixlddz3667ba1iyqck3c0dkpvd-gnugrep-3.11/bin/grep -q '1915:521f Nordic Semiconductor ASA Open DFU Bootloader'; then
      echo "Device is currently connected via USB" &&
      device_node=$(/nix/store/7y59hzi3svdj1xjddjn2k7km96pifcyl-findutils-4.10.0/bin/find /dev/serial/by-id/usb-Nordic_Semiconductor_Open_DFU_Bootloader_C1E8D2B54E6C-*) &&
      echo "We found a DFU Bootloader for device $device_node"

      n=/nix/store/byh3jmf68mav7nxsybcaidg9rici2p4m-nrfutil-1.0/bin/nrfutil
      for p in $("$n" search| grep 'Not installed'| awk '{print $1}'); do
        "$n" install "$p"
      done
      set -x
      
      keydir=/configuration/secrets/Thread/nrf52840
      key=$keydir/private.pem
      
      if [ ! -f "$key" ]; then 
        "$n" nrf5sdk-tools keys generate "$key"
        # /nix/store/rjzx8v679rwd6dsb6s08iy3j2rrax72s-openssl-3.4.1-bin/bin/openssl ecparam -name prime256v1 -genkey -noout -out "$key"
      fi &&

      app=/nix/store/10lclbfxncczar6i0789n473am6rlrcy-ot-nrf528xx-unstable-2025-05-23/bin/ot-rcp.hex &&

      printf 'Using hex file: %s\n' "$app" &&
      
      output=$(pwd)/thread_rcp_dfu.zip &&
      printf 'Generating DFU package: %s\n' "$output" &&

      "$n" pkg generate \
      --hw-version 52 \
      --sd-req 0x00 \
      --application "$app" \
      --key-file "$key" \
      --application-version 1 \
      "$output" &&
      dfu_description=$("$n" pkg display "$output") &&
      if printf '%s' "$dfu_description" | /nix/store/gqmr3gixlddz3667ba1iyqck3c0dkpvd-gnugrep-3.11/bin/grep 'sd_req: 0x00'; then
        echo "Good, this is not a SoftDevice"
      fi &&
      echo "" &&
      echo "$dfu_description"
      
    else
      echo "No DFU Bootloader found in dmesg output; nothing to do." 
    fi
  fi

Then, I wanted to flash via:

#!/bin/sh
if [ -z "$1" ]; then
  echo "Usage: $0 firmware.dfu.zip"
  exit 1
fi

FW=$1
set -x

printf "Flashing firmware '%s' to nRF52840 USB Dongle in DFU mode...\n" "$FW"
n=/nix/store/byh3jmf68mav7nxsybcaidg9rici2p4m-nrfutil-1.0/bin/nrfutil
# Flash via USB DFU
"$n"  dfu usb-serial -pkg "$FW" -p /dev/ttyACM0

if [ $? -eq 0 ]; then
  echo "Flash successful."
else
  echo "Flashing failed."
  exit 3
fi

I saw output saying "device programmed" with  a progress bar before it that went to 100%, suggesting that at least *something* was flashed. Before (from the distributor) the device was in DFU mode, showing a dimming orange LED and it would show up in both dmesg and lsusb (as checked by the code), but afterwards it just seems dead/bricked. 

So, how do I recover this and how do I accomplish what really should have been an easy task of flashing an Openthread Border Router RCP (openthread.io/.../border-router) onto the device such that I can achieve my end goal of just being able to use Matter devices? 

The code I used to build the ot-tcp.hex file (the artefact used in the code above creating the DFU zip file) is visible below:

# code used to build ot-rcp.hex

bash build nrf52840 USB_trans

arm-none-eabi-objcopy -O ihex $OT_CMAKE_BUILD_DIR/bin/ot-rcp $NIX_BUILD_TOP/bin/ot-rcp.hex

I feel like I have done nothing wrong and followed all instructions, but despite best intentions, the device still is bricked

Overall, I consider it a _horrible_ developer experience for trying to do something which should have been simple (adding an OBTR to the network).

I am aware other people asked somewhat similar questions, but my setup is probably somewhat unique. Version information of nrfutil:

$ /nix/store/byh3jmf68mav7nxsybcaidg9rici2p4m-nrfutil-1.0/bin/nrfutil --version
nrfutil 8.0.0 (54d8087 2025-01-07)
commit-hash: 54d8087a38b73b6e56942fb1b024b62365f06731
commit-date: 2025-01-07
host: x86_64-unknown-linux-gnu
build-timestamp: 2025-01-07T14:26:42.070728557Z
classification: nrf-external

So, the questions then are:

1. How do I recover to factory settings (assuming I have little to no tools right now, but I can buy tools)? I pressed the white button (there are no other buttons visible) in an attempt to reset to factory settings.
2. What do I need to flash Openthread RCP on it such that it *does* work?
3. Why is it even possible to have a successful flash that bricks the device in the first place? E.g. why is there no simulation of some kind to make sure the resulting flashed device does something useful?
4. If I need to buy something to make this work, what?

[bricked]

OK, so is there some script already that actually results in a Thread 1.3 (or whatever is newest) firmware that I can flash in the same way for any operating system (I can port it to mine)? So, last time I depended on you providing a .hex file. 

I want to add some extra Thread 1.3 devices, but AFAIK your  5008.nrf52840_dongle_thread_coprocessor.hex is already too old. 

[Hung Bui]

Hi,

This is very old thread. I would suggest you to create a new ticket for this. 
I would suggest to use a nRF52840 DK to get started instead of using the dongle. The dongle is not a platform for developing application.