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ENG | Getting started with NRF52840 Dongle - Welcome to hell.

How hard could be to compile and upload blinky in nRF ecosystem?

Posted Updated
nRF52840 USB Dongle
nRF52840 USB Dongle
By Pavel Peřina
7 min read
ENG | Getting started with NRF52840 Dongle - Welcome to hell.

Why to get it

I expected the nRF52840 dongle might be ideal for low power data loggers, BLE sensors, or weather stations. Arduino can suffice for data logger, but when I build temperature sensor based on Raspberry Pi Pico in previous project, I found need of USB charger and data transfers over WiFi and HTTP maybe a bit overkill. Again, it gets the job done, but why not to learn something new?

If the format of USB dongle is the most suitable is something I haven’t decided yet. Another piece from Xiao Seeed is on the way at the time of writing.

What surprised me was how complicated things could be when there are three tools for everything - each in various phases of obsolescence or early adoption - leaving the user to realize what actually works and use the right combination. Fully supported systems are Windows 10, Ubuntu 22.04 LTS and some version of MacOS.

Where to get it

I got nRF52840 Dongle (PCA10059) from AliExpress, it can be obtained elsewhere, but Mouser or Farnell required to pay significant money for small/cheap orders and I’m not sure why I did not ordered it from TME which has about the same price as AliExpress.

First pluggin in

When first plugged-in it’s detected as serial USB device which constantly transmits some binary data. USB ID is 1915:522a and nRF Sniffer for Bluetooth LE on Linux. Maybe it has this functionality uploaded as firmware. Indeed, it does and it can be found on official website

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dmesg

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[3523765.421854] usb 1-2: new full-speed USB device number 3 using xhci_hcd
[3523765.549294] usb 1-2: New USB device found, idVendor=1915, idProduct=522a, bcdDevice= 2.04
[3523765.549309] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[3523765.549316] usb 1-2: Product: nRF Sniffer for Bluetooth LE
[3523765.549321] usb 1-2: Manufacturer: ZEPHYR
[3523765.549325] usb 1-2: SerialNumber: 3B76E4C74F808A66
[3523766.162209] cdc_acm 1-2:1.0: ttyACM0: USB ACM device
[3523766.162240] usbcore: registered new interface driver cdc_acm
[3523766.162242] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters

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lsusb

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Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 1915:522a Nordic Semiconductor ASA nRF Sniffer for Bluetooth LE
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub

Actually, the USB ID changes with firmware, so it’s a bit irrelevant.

Installing tools

This is pretty easy. Documentation is comprehensive so in theory everything should be fine. Except documentation lacks step-by-step guides, is full of references, and in the end you don’t even know what to install and why the fuck it does not work.

  1. Download and install Segger JLink. In my case I downloaded RPM (I’m using Fedora 42, btw) and installed it by sudo rpm -i JLink_Linux_V838_x86_64.rpm). It says “This package provides software tools for SEGGER J-Link debug probes.” - don’t ask me.
  2. Download nrfutil, copy it to your ~/bin directory and make it executable chmod +x nrfutil. Then type nrfutil install nrf5sdk-tools and nrfutil install device
  3. Download and upgrade nRF Connect for Desktop Apps, you may copy it to your ~/bin and make it executable. Don’t expect much from it, so you won’t be disappointed. Basically nothing works. It will create some folders in ~/opt and who knows where else.
  4. Install nRF Connect for VS Code extension for VS code. It will take some time. Some files will appear in ~/ncs directory - compilers, Zephyr RTOS. SDK version 3.0.1 had some problems, 2.9.1 worked.
  5. Visit https://github.com/NordicSemiconductor/nrf-udev and adapt. It should make USB device accessible for all users.
    • I installed it this way:
    • And verified it:

Compiling blinky

I guess you need to open extension menu, go through Get Started with the nRF Connect SDK checklist on Welcome screen, find that in Applications, there is Add build configuration where you select nRF52840 Dongle from long list of devices which is not in alphabetical order (yes, i’m still complaining) and build it. But you need to build it from ACTIONS->Build instead of default (complaining again).

Switching to Bootloader mode

Some wise guy decided that it would be great fun to add invisible reset button next to very visible user button. Documentation does not even explicitly state how to enter boot mode, so you have to google it once you encounter a hint that such a thing exists.

Programmer requires bootloader mode

When you look carefully RESET button is located next to SW1, it does not look like a button and it’s pressed from the rear/aft side.

In the end, unlike Raspberry Pi Pico, you can press this button at any time, not just while plugging it in, so maybe it’s good it cannot be pressed by accident. But there are so many annoyances like that and every one of them takes ten minutes to realize and google solution.

Checking boot mode

Flashing firmware

Struggle does not end here. I assume that developers of toolset for nRF ecosystem are a bunch of sadistic psychopats or incompetent monkeys.

As before, nrfutil device list can see it. NRF programmer can see it too. Now it does not even complain about boot mode.

Naively flashing it from command line does not work neither

What actually works is Programmer from nRF Connect for Desktop Apps, where you can drop file (after clearing old ones).

Wait, there is a documentation specific for nRF52xxx series. It mentions reset button and options of uploading firmware and compiling it with west tool which is a part of Zephyr. But I did not found it first.

Conclusion

Well, maybe using Zephyr and standard tools instead of Nordic tools (which hides standard ones under the hood) is not a bad idea. I was already considering it for Raspberry Pi Pico and C++, but then I found MicroPython more comfortable and sufficient. Time to explore it?

Screw it. Back to gardeing and replanting chilli. It’s more satisfying. I wasted like six hours uploading blinky and right now I’m not in the mood to continue.

Next day I tried programming device in a way described in a documentation. VICTORY!

Addendum (2025-06-03): Recap and quick comparison with XIAO Seeed

nRF52840 Dongle

  • Preloaded nRF Sniffer for Bluetooth LE firmware
  • Enters USB DFU Bootloader mode by holding RESET (not SW1) button
  • In bootloader mode appears as ASA Open DFU Bootloader with USB VID:PID 1915:521f
  • Has Visual Studio Code extension, which contains ARM compiler and Zephyr OS
  • Has nRF Connect desktop app (appimage) with tools such as programmer.
  • Can be flashed by Programmer (part of nRF Connect for Desktop) or
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    nrfutil nrf5sdk-tools pkg generate --hw-version 52 --sd-req=0x00 --application merged.hex --application-version 1 <package.zip>
nrfutil nrf5sdk-tools dfu usb-serial -pkg <package.zip> -p /dev/ttyACM0`
  • NOTE: Segger J-Link is likely not needed at all - at least for regular flashing. It requires hardware and soldering wires to the dongle’s SWD (Serial Wire Debug) pins and is typically only needed for bootloader recovery or full flash erase on ARM Cortex-M devices. I found this later. It might be prerequisite for nRF Connect app thou.

XIAO nRF52840

  • Preloaded Arduino firmware
  • Comes with UF2 bootloader
  • Bootloader mode is accessed by pressing RST button twice - it appears as 32MB usb drive (VID:PID 2886:0045)
  • Compatible with Arduino, MicroPython and others.
  • It is possible to use it with Seeed Studio XIAO expansion board.
  • Has Getting started tutorial so I hopefully would not need to write my own notes 😀

XIAO Seeed nRF52840 with expansion board

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electronics nrf52
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