Adafruit ItsyBitsy nRF52840

The Adafruit ItsyBitsy-nRF52840 is a small ARM development board based on the Nordic Semiconductor nrf52840 processor.


Interface Hardware Supported TinyGo Support
Bluetooth YES YES

Machine Package Docs

Documentation for the machine package for the ItsyBitsy-nRF52840



The ItsyBitsy-nRF52840 comes with the UF2 bootloader already installed.

PLEASE NOTE that for a good experience using TinyGo on your board you must be running version 0.4.1 or above of the UF2 bootloader on the board. For more information, see below

CLI Flashing

  • Plug your ItsyBitsy-nRF52840 into your computer’s USB port.

  • Flash your TinyGo program to the board using this command:

    tinygo flash -target=itsybitsy-nrf52840 [PATH TO YOUR PROGRAM]
  • The ItsyBitsy-nRF52840 board should restart and then begin running your program.


If you have troubles getting your ItsyBitsy-nRF52840 board to receive code, try this:

  • Press the “RESET” button on the board two times to get the ItsyBitsy-nRF52840 board ready to receive code.

  • The ItsyBitsy-nRF52840 board will appear to your computer like a USB drive.

  • Now try running the command:

    tinygo flash -target=itsybitsy-nrf52840 [PATH TO YOUR PROGRAM]

Once you have updated your ItsyBitsy-nRF52840 board the first time, after that you should be able to flash it entirely from the command line.


You can use the USB port to the ItsyBitsy-nRF52840 as a serial port. UART0 refers to this connection.

For an example that uses the built-in Neopixel LEDs, take a look at the TinyGo drivers repository located at

Bluetooth support is now available for the ItsyBitsy-nRF52840 board. See for more information.

Updating the UF2 bootloader

This board uses a UF2 bootloader created by Adafruit:

We recommend bootloader version 0.4.1 or above. You can check what version is installed on your board by double-clicking the button on the board to launch the bootloader. When you do this, a USB volume that should automatically be mounted on your computer. Check the file named “INFO_UF2.TXT” on that drive. The bootloader firmware version should be listed in that file, for example:

UF2 Bootloader 0.4.1 lib/nrfx (v2.0.0) lib/tinyusb (0.6.0-272-g4e6aa0d8) lib/uf2 (remotes/origin/configupdate-9-gadbb8c7)
Model: Adafruit ItsyBitsy nRF52840 Express
Board-ID: nRF52840-ItsyBitsy-revA
SoftDevice: S140 version 6.1.1
Date: Jan 19 2021

To update the bootloader, you will need to install the adafruit-nrfutil program.

You can install it by running:

pip3 install --user adafruit-nrfutil

Once you have installed the adafruit-nrfutil program, download the firmware here:

Unzip the files in this zip file and save them to a convenient location.

Plug in your board to your computer’s USB port.

Now we are ready to update the firmware. Run a command something like the following, adjusting for any difference based on where you have saved the files, and what your serial port is named:

 adafruit-nrfutil --verbose dfu serial --package -p /dev/ttyACM0 -b 115200 --singlebank --touch 1200

Note that you should be flashing the board using the zip file that was contained within the zip file that you downloaded, NOT the file that you downloaded.

Once you have flashed the board with the adafruit-nrfutil it should restart the board with the new bootloader. You only need to do this update once, and then from that point on the new bootloader will be active.

Last modified December 29, 2021: reference: unify notation for targets (febb8c5)