Adafruit nRF52 Bootloader

This repository is a fork of the official Adafruit repository. My keyboards use external LED indicators, so I have made changes that allow them to display the bootloader status. The original code supports blinking only a single LED, whereas my version adds the ability to work with multiple indicators. If you have any questions unrelated to indicators, you should probably contact the creators of the original repository.

I do not describe some details that are not important to me. I am only interested in building UF2 bootloaders for nRF52 locally in Fedora or using GitHub Actions.

My configs

• nice_nano_LED
• nice_nano_RGB
• kabarga
• PNCATEHO MK Dose

Burn & Upgrade with pre-built binaries

In most cases, you just need to connect the keyboard to your computer, double-press the MCU reset button, and copy the UF2 bootloader file to the newly appeared device. If you need to flash the bootloader using a programmer, follow this guide.

How to build

You should only continue if you are looking to develop bootloader for your own. You must have have a J-Link available to "unbrick" your device.

Creating a Configuration with Regular LEDs

To create your own bootloader variant for n!n, copy the src/boards/nice_nano_LED folder and rename it, for example, to kabarga. Then, edit the board.h file inside this folder.

Set LED_PRIMARY_PIN and LED_SECONDARY_PIN to the appropriate LED pins. Also, replace the following lines:

#ifndef _NICENANO_LED_H  
#define _NICENANO_LED_H  

with

#ifndef _KABARGA_H  
#define _KABARGA_H  

At the bottom of the file, you can change the device name.

Finally, build your bootloader using the command:

BOARD=kabarga all

The lighting parameters are configured in the src/boards/boards.c file, starting from line 365.

Creating a Configuration with Addressable LEDs

To create your own bootloader variant for n!n, copy the src/boards/nice_nano_RGB folder and rename it, for example, to kabarga_RGB. Then, edit the board.h file inside this folder.

Set LED_NEOPIXEL and LED_NEOPIXEL to the appropriate LED pins. Set the NEOPIXELS_NUMBER parameter (number of LEDs) and BOARD_RGB_BRIGHTNESS (their brightness).

Also, replace the following lines:

#ifndef _NICENANO_RGB_H  
#define _NICENANO_RGB_H  

with

#ifndef _KABARGA_RGB_H  
#define _KABARGA_RGB_H  

At the bottom of the file, you can change the device name.

Finally, build your bootloader using the command:

BOARD=kabarga-rgb all

The lighting parameters are configured in the src/boards/boards.c file, starting from line 396.

Building with GitHub Actions

• Fork this repository.
• Make the necessary changes.
• Commit and push.
• Enable GitHub Actions on the corresponding tab.
• Create an empty release with the tag 0.9.2.
• Wait for GitHub Actions to finish building your bootloader.

Local Build

I use Fedora, but the commands will be similar on other distributions.

Prerequisites

sudo dnf install python3-pip gcc-arm-none-eabi make arm-none-eabi-newlib arm-none-eabi-gcc-cs git --skip-unavailable    
pip3 install --user adafruit-nrfutil intelhex

Build:

Firstly clone this repo with following commands

cd $HOME
git clone https://github.com/aroum/nRF52_Bootloader_custom_LED
cd nRF52_Bootloader_custom_LED
git submodule update --init

Then build it with make BOARD={board} all, for example:

make BOARD=feather_nrf52840_express all

For the list of supported boards, run make without BOARD= :

$ make
You must provide a BOARD parameter with 'BOARD='
Supported boards are: feather_nrf52840_express feather_nrf52840_express pca10056
Makefile:90: *** BOARD not defined.  Stop

Here, {board} matches the name of the configuration folder in src/boards/{board}.

The bootloader file can be found here: _build/build-kabarga/update-kabarga_bootloader-XXX.uf2

Common makefile problems

If you get the following error ...

lib/sdk11/components/libraries/bootloader_dfu/bootloader_settings.c: In function 'bootloader_mbr_addrs_populate':
lib/sdk11/components/libraries/bootloader_dfu/bootloader_settings.c:45:7: error: array subscript 0 is outside array bounds of 'const uint32_t[0]' {aka 'const long unsigned int[]'} [-Werror=array-bounds=]
45 | if (*(const uint32_t *)MBR_BOOTLOADER_ADDR == 0xFFFFFFFF)
compilation terminated due to -Wfatal-errors.
cc1: all warnings being treated as errors
make: *** [Makefile:412: _build/build-feather_nrf52840_express/bootloader_settings.o] Error 1`

You are probably using arm-none-eabi-gcc version 14 or higher. You can check it with the following command:

arm-none-eabi-gcc --version

If the version is 15 or higher, you need to modify one line in the Makefile. Replace:

filter 12.% 13.% 14.%,$

with:

filter 12.% 13.% 14.% 15.%,$

Here is an example command to do this automatically:

sed -i 's/ifneq (,$(filter 12.% 13.% 14.%,$(shell \$(CC) -dumpversion 2>\/dev\/nul
l)))/ifneq (,$(filter 12.% 13.% 14.% 15.%,$(shell \$(CC) -dumpversion 2>\/dev\/null)))/g' "Makefile"

original issues