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Adafruit code for the Nordic nRF52 BLE SoC on Arduino


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Purpose of This Fork

This fork is necessary when compiling the firmware for the ErgoBlue keyboard. See the firmware page for more details.

Arduino Core for Adafruit Bluefruit nRF52 Boards

This repository contains the Arduino BSP for Adafruit nRF52 series:

BSP Installation

There are two methods that you can use to install this BSP. We highly recommend the first option unless you wish to participate in active development of this codebase via Github.

Recommended: Adafruit nRF52 BSP via the Arduino Board Manager

  1. Download and install the Arduino IDE (At least v1.6.12)
  2. Start the Arduino IDE
  3. Go into Preferences
  4. Add as an 'Additional Board Manager URL'
  5. Restart the Arduino IDE
  6. Open the Boards Manager from the Tools -> Board menu and install 'Adafruit nRF52 by Adafruit'
  7. Once the BSP is installed, select 'Adafruit Bluefruit nRF52 Feather' from the Tools -> Board menu, which will update your system config to use the right compiler and settings for the nRF52.

Optional (Core Development): Adafruit nRF52 BSP via git

  1. Install BSP via Board Manager as above to install compiler & tools.
  2. Delete the core folder nrf52 installed by Board Manager in Adruino15, depending on your OS. It could be
  • macOS : ~/Library/Arduino15/packages/adafruit/hardware/nrf52
  • Linux : ~/.arduino15/packages/adafruit/hardware/nrf52
  • Windows: %APPDATA%\Local\Arduino15\packages\adafruit\hardware\nrf52
  1. cd <SKETCHBOOK>, where <SKETCHBOOK> is your Arduino Sketch folder:
  • macOS : ~/Documents/Arduino
  • Linux : ~/Arduino
  • Windows: ~/Documents/Arduino
  1. Create a folder named hardware/Adafruit, if it does not exist, and change directories to it
  2. Clone this repo: git clone
  3. Restart the Arduino IDE
  4. Once the BSP is installed, select 'Adafruit Bluefruit nRF52 Feather' from the Tools -> Board menu, which will update your system config to use the right compiler and settings for the nRF52.

Adafruit's nrfutil tools

adafruit-nrfutil (derived from Nordic pc-nrfutil) is needed to upload sketch via serial port.

  • For Windows and macOS, pre-built executable binaries are included in the BSP at tools/adafruit-nrfutil/. It should work out of the box.

  • Linux user need to run follow command to install it from PyPi

    $ pip3 install adafruit-nrfutil --user


Arduino BLE Application Support

This Arduino core contains basic BLE peripheral mode helper classes and an initial peripheral mode API. These helper classes and APIs aim to make it easier to work with the Nordic SoftDevice that contains Nordic's official Bluetooth Low Energy stack. You are also free to use the Nordic SDK to generate your own example code, since all of the SoftDevice header files are included in your projects by default.

To see a list of example sketches that make use of these helper classes, select the appropriate board from the Tools > Board menu item, and then in the Examples menu look for the list of examples sketched for the selected board.

Bootloader Support

Upgrade existing Bootloader

Bluefruit's Bootloader is self-upgradable, you could upgrade to the latest Bootloader + Softdevice using the serial port within Arduino IDE.

  • Select Tools > Board > Adafruit Bluefruit Feather52
  • Select Tools > Programmer > Bootloader DFU for Bluefruit nRF52
  • Select Tools > Burn Bootloader
  • WAIT until the process complete ~30 seconds

Note: close the Serial Monitor before you click "Burn Bootloader". Afterwards, you shouldn't close the Arduino IDE, unplug the Feather, launch Serial Monitor etc ... to abort the process. There is a high chance it will brick your device! Do this with care and caution.

Burning new Bootloader

To burn the bootloader from within the Arduino IDE, you will need the following tools installed on your system and available in the system path:

Check to make sure you can run nrfjprog from your terminal/command prompt

macOS Note At present, you will need to create a symlink in /usr/local/bin to the nrfjprog tool wherever you have added it. You can run the following command, for example:

$ ln -s $HOME/prog/nordic/nrfjprog/nrfjprog /usr/local/bin/nrfjprog

Once the tools above have been installed and added to your system path, from the Arduino IDE:

  • Select Tools > Board > Adafruit Bluefruit Feather52
  • Select Tools > Programmer > J-Link for Feather52
  • Select Tools > Burn Bootloader with the board and J-Link connected

If you wish to modify bootloader to your own need, check out its repo here Adafruit_nRF52_Bootloader

Manually Burning the Bootloader via nrfjprog

The bootloader hex file can be found at bin/bootloader run the command as follows:

$ nrfjprog -e -f nrf52
$ nrfjprog --program feather_nrf52832_bootloader.hex -f nrf52
$ nrfjprog --reset -f nrf52

Misc Notes

nRF52DK Jlink Issue on macOS

If developing with the nRF52DK on macOS, there is a bug where only 64 bytes can be sent over the USB CDC interface, which will prevent you from using the serial bootloader from the Arduino IDE with an error like this:

Upgrading target on /dev/cu.usbmodem1421 with DFU package /private/var/folders/86/hb2vp14n5_5_yvdz_z8w9x_c0000gn/T/arduino_build_267869/ Flow control is disabled.

Timed out waiting for acknowledgement from device.

Failed to upgrade target. Error is: No data received on serial port. Not able to proceed.

Possible causes:
- bootloader, SoftDevice or application on target does not match the requirements in the DFU package.
- baud rate or flow control is not the same as in the target bootloader.
- target is not in DFU mode. If using the SDK examples, press Button 4 and RESET and release both to enter DFU mode.

To resolve this and enable 512 byte packets over USB serial, you must disable the Mass Storage Device interface on the JLink-OB, which will free up two of the 512 byte USB end points. (For details see this article.)

You can do so by running JLinkExe from the command line, and then entering the MSDDisable command, and power cycling your nRF52DK. To re-enable MSD support, do the same but enter the MSDEnable command.


This core is based on Arduino-nRF5 by Sandeep Mistry, which in turn is based on the Arduino SAMD Core.

The following libraries are used:


Adafruit code for the Nordic nRF52 BLE SoC on Arduino









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