NRF52840

Project NRF52840
Running Arduino with platformio on NRF52840
Status	In progress
Contact	bertrik
Last Update	2026-01-12

Intro

This page is about getting inexpensive NRF52840 boards to work with Arduino and platformio.

NRF52840 is a nice platform:

• low-power
• inexpensive
• decent amount of flash (1024k), RAM (256k) and CPU cycles (64 MHz)
• support various radio protocols like zigbee, ble, thread, enhanced shockburst
• built-in support for quadrature counting
• 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 sometimes 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, over USB-serial
  • Mass storage UF2, 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
  • Risk of accidentally overwriting the bootloader, with UF2 flash offsets sometimes being absolute, sometimes being relative

Hardware

pinout

The boards I have are the "promicro" and "supermini". These boards look basically identical hardware-wise.

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.

The blue LED appears to flash independently of software, this is probably the charge circuit behaving randomly without a battery present. The red LED appears to be under software control.

Pinout/schematic: https://nicekeyboards.com/docs/nice-nano/pinout-schematic

bootloader

The INFO_UF2.TXT says (after double-tap reset):

 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: S140 version 6.1.1
 Date: Jun 19 2021

The CURRENT.UF2 file is 1.4 MB

Kernel log says:

[509372.005339] usb 1-2.3: new full-speed USB device number 96 using xhci_hcd
[509372.132351] usb 1-2.3: New USB device found, idVendor=239a, idProduct=00b3, bcdDevice= 1.00
[509372.132361] usb 1-2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[509372.132364] usb 1-2.3: Product: nice!nano
[509372.132366] usb 1-2.3: Manufacturer: Nice Keyboards
[509372.132368] usb 1-2.3: SerialNumber: 98D93A272A6CCC7D
[509372.187474] cdc_acm 1-2.3:1.0: ttyACM0: USB ACM device
[509372.190177] usb-storage 1-2.3:1.2: USB Mass Storage device detected
[509372.190467] scsi host3: usb-storage 1-2.3:1.2
[509373.200470] scsi host3: scsi scan: INQUIRY result too short (5), using 36
[509373.200481] scsi 3:0:0:0: Direct-Access     Adafruit nRF UF2          1.0  PQ: 0 ANSI: 2
[509373.200825] sd 3:0:0:0: Attached scsi generic sg0 type 0
[509373.202317] sd 3:0:0:0: [sdb] 65801 512-byte logical blocks: (33.7 MB/32.1 MiB)
[509373.202556] sd 3:0:0:0: [sdb] Write Protect is off
[509373.202559] sd 3:0:0:0: [sdb] Mode Sense: 03 00 00 00
[509373.202782] sd 3:0:0:0: [sdb] No Caching mode page found
[509373.202784] sd 3:0:0:0: [sdb] Assuming drive cache: write through
[509373.296933]  sdb:
[509373.297002] sd 3:0:0:0: [sdb] Attached SCSI removable disk

Software

Working platformio example project for the nice!nano and supermini/promicro nrf52840 clones: https://github.com/bertrik/nicenano-example

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
• nRFMicro Arduino Core:
  • Meant for integration with Arduino IDE, not platformio!
  • See https://github.com/pdcook/nRFMicro-Arduino-Core
  • Uses https://github.com/NordicSemiconductor/nrfx for NRF52840 specific drivers
• Platformio support for supermini:
  • Focused on platformio
  • https://github.com/ICantMakeThings/Nicenano-NRF52-Supermini-PlatformIO-Support
  • Bit awkward installation (copy/overwrite files inside existing platformio folder)
• https://docs.nordicsemi.com/bundle/ncs-3.1.0/page/zephyr/boards/others/promicro_nrf52840/doc/index.html pro-micro information from Nordic Semi

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!?!!!