NRF52840

Project NRF52840
File:Nopicture.jpg
Investigating Arduino on inexpensive NRF52840 boards
Status	In progress
Contact	bertrik
Last Update	2025-11-29

Intro

NRF52840 is potentially a very nice platform:

• low-power. quick wake-up
• inexpensive
• decent amount of flash (1024k), RAM (256k) and CPU cycles (64 MHz)
• support various radio protocols like zigbee, ble, thread, matter, enhanced shockburst
• built-in support for quadrature counting
• looks like it can run arduino too

However the eco-system of inexpensive boards is a complicated landscape:

• AliExpress sellers offer "promicro" and "supermini" board with unclear characteristics
• LEDs are often swapped (blue = hardware charge, red = software led?)
• Various firmware upload interface options (which one to use?):
  • Using nrfutil, sends a .zip file containing various parts
  • Serial DFU, used by nrfutil?
  • Mass storage UF2, possibly activated using the double-reset
  • SWD debug interface (requires soldering!)
• Confusing situation regarding bootloaders:
  • Most boards seem to come with a modified version of a bootloader meant for another type of board
  • Type of bootloader depends on type of firmware you want to run, "ZMK", Arduino using Arduino IDE, Arduino using platformio
  • Space for "SoftDevice" needs to be reserved, what is this?
  • Risk of accidentally overwriting the bootloader, with UF2 flash offsets sometimes being absolute, sometimes being relative
  • Even multiple levels of bootloader? Like the normal one during application and another one using the double-reset method?

Hardware

The boards I have are the "promicro" and "supermini".

There is a 4-pad connector to program it using SWD (VDD/SWD/SDC/GND). This can be used to write the bootloader for example. The pads have a spacing of 1.5mm.

Software

Links:

• Nordic technical documentation: https://docs.nordicsemi.com/category/nrf52840-category
• Here is a wiki full of useful information on specific boards: https://github.com/joric/nrfmicro/wiki
  • Specifically the supermini https://github.com/joric/nrfmicro/wiki/Alternatives#supermini-nrf52840
• See also https://github.com/pdcook/nRFMicro-Arduino-Core
• https://github.com/ICantMakeThings/Nicenano-NRF52-Supermini-PlatformIO-Support

My promicro board currently has bootloader 0.6.0:

 UF2 Bootloader 0.6.0 lib/nrfx (v2.0.0) lib/tinyusb (0.10.1-41-gdf0cda2d) lib/uf2 (remotes/origin/configupdate-9-gadbb8c7)
 Model: nice!nano
 Board-ID: nRF52840-nicenano
 SoftDevice: not found
 Date: Jun 19 2021

My supermini board came with bootloader 0.6.0:

 UF2 Bootloader 0.6.0 lib/nrfx (v2.0.0) lib/tinyusb (0.10.1-41-gdf0cda2d) lib/uf2 (remotes/origin/configupdate-9-gadbb8c7)
 Model: nice!nano
 Board-ID: nRF52840-nicenano
 SoftDevice: not found
 Date: Jun 19 2021

Getting 'circuitpython' to work:

• Here's a page on making it work on nicenano: https://circuitpython.org/board/nice_nano/
• HOWEVER, it also says "On nRF boards, CircuitPython 8.2.0 and later require UF2 bootloader version 0.6.1 or later. Older bootloaders cannot load the firmware. See Update UF2 Bootloader below.". Guess what bootloader came with my board ... 0.6.0
• They point you to https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases/tag/0.9.2 but now what!?!!!