nRF54L Bootloader

BLE DFU bootloader for Nordic nRF54L series (nRF54L15, nRF54L10, nRF54L05).

Based on the Nordic nRF5 SDK bootloader architecture, ported to nRF54L with SoftDevice S145.

Supported Boards

Board	Target	MCU
nRF54L15-DK	nrf54l15dk	nRF54L15
nRF54L10-DK	nrf54l10dk	nRF54L10
nRF54L05-DK	nrf54l05dk	nRF54L05
XIAO nRF54L15	xiao_nrf54l15	nRF54L15
XIAO nRF54L15 Sense	xiao_nrf54l15_sense	nRF54L15

Features

• DFU over Serial (UART) and OTA (BLE)
• Self-upgradable via Serial and OTA (bootloader + SoftDevice)
• Dual bank firmware updates (disabled by default)
• Signed firmware updates (disabled by default)
• Watchdog feed-through during DFU

Note: nRF54L has no USB peripheral, so there is no UF2 or CDC support.

How to use

The bootloader checks two pins on reset:

• DFU = LOW, FRST = HIGH: Enter serial DFU mode
• DFU = LOW, FRST = LOW: Enter OTA DFU mode (for Nordic nRF Connect/Toolbox)
• DFU = HIGH, FRST = HIGH: Boot application if present, otherwise enter DFU
• Double Reset within 500 ms: Enter DFU mode

On the nRF54L15-DK, DFU is Button1 and FRST is Button2.

The application can also trigger DFU via the GPREGRET register:

void reset_to_dfu(void) {
    NRF_POWER->GPREGRET = 0x4e; // 0xA8 for OTA
    NVIC_SystemReset();
}

Building

Prerequisites

• ARM GCC toolchain (12.x or later)
• CMake 3.17+
• Nordic nRF Command Line Tools (for flashing)

Clone

git clone --recurse-submodules https://github.com/caveman99/nRF54_Bootloader.git

Build with CMake

cmake -B _build -DBOARD=nrf54l15dk -DCMAKE_BUILD_TYPE=MinSizeRel
cmake --build _build

Output: _build/bootloader.hex

Build with Make

make BOARD=nrf54l15dk all

Flash

Flash bootloader via J-Link:

make BOARD=nrf54l15dk flash

Flash SoftDevice:

make BOARD=nrf54l15dk flash-sd

DFU via serial:

make BOARD=nrf54l15dk SERIAL=/dev/ttyACM0 flash-dfu

If using pyocd:

make BOARD=nrf54l15dk FLASHER=pyocd flash

Build options

Option	Default	Description
DUALBANK_FW	0	Split flash into two banks for safe updates
SIGNED_FW	0	Require signed firmware packages
DEFAULT_TO_OTA_DFU	0	Default to OTA DFU instead of serial

Signed firmware

Generate a signing key:

nrfutil keys --gen-key stored_key.pem
nrfutil keys --show-vk code stored_key.pem

Build with signing enabled:

make BOARD=nrf54l15dk SIGNED_FW=1 SIGNED_FW_QX='...' SIGNED_FW_QY='...'

Create a signed DFU package:

nrfutil dfu genpkg --dev-type 0x0054 --sd-req 0x3024 --application app.hex --key-file stored_key.pem app_dfu.zip

Upload via serial:

nrfutil dfu serial -pkg app_dfu.zip -p /dev/ttyACM0 -b 115200

Adding a new board

1. Create src/boards/<board_name>/ with:

   • board.h — pin definitions (LEDs, buttons, UART)
   • board.cmake — set MCU_VARIANT (nrf54l15, nrf54l10, or nrf54l05)
   • board.mk — set MCU_SUB_VARIANT
   • pinconfig.c — board metadata

2. Build with cmake -DBOARD=<board_name> ...

See existing boards in src/boards/ for reference.

License

MIT License. See LICENSE for details.