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@defgroup boards_common_adafruit-nrf52-bootloader Adafruit nRF52 Bootloader Common @ingroup boards_common @brief Common Flashing Description for the Adafruit nRF52 Bootloader
Flashing the Board
The board is flashed using its on-board UF2 boot loader by default.
The boot loader will present a mass storage device that has to be mounted to /media/MDK-DONGLE so
uf2conv.py can find it. If you have an auto-mounter installed this will happen automatically.
The rest of the process is automated in the usual way with e.g. BOARD=feather-nrf52840.
Example with hello-world application:
make BOARD=feather-nrf52840 -C examples/basic/hello-world flash term
If RIOT is already running on the board, it will automatically reset the CPU and enter the bootloader. If some other firmware is running or RIOT crashed, you need to enter the bootloader manually by double-tapping the board's reset button while the device is connected.
The board definitions with RIOT retain the SoftDevice firmware blob shipped with
the original Adafruit nRF52 Bootloader that is used by i.a. Arduino and
CircuitPython but not used by RIOT. If you want to override the SoftDevice
to avoid having closed source software on your microcontroller or if you need
the additional space, you can specify the UF2_SOFTDEV=DROP option in your
make command. Be aware that you have to reflash the SoftDevice if you want
to use it in the future!
make UF2_SOFTDEV=DROP BOARD=feather-nrf52840 -C examples/basic/hello-world flash term
If your board features a non-standard SoftDevice version, you can specify it
with the UF2_SOFTDEV option as well. Currently supported are i.a. SD611
for SoftDevice Version 6.1.1 and SD730 for Version 7.3.0.
Setting the wrong SoftDevice version might corrupt the SoftDevice and
make a reflash of the SoftDevice necessary. Do not change it unless you know
what you're doing!
Otherwise see the Flashing section in @ref boards_common_nrf52. The easiest way is to use an external Segger J-Link Programmer connected to the SWD Connector.
(Re-)Flashing the UF2 Bootloader
To flash the UF2 bootloader (if it is no longer present on your board),
you need to have nrfjprog installed,
connect a jlink to your BOARD and execute the following commands.
@note The Adafruit nRF52 Bootloader uses other board names than RIOT. The
feather-nrf52840 for example is called feather_nrf52840_express.
Be sure to check the boards/ subfolder in the bootloader directory
to find out the correct board name.
git clone git@github.com:adafruit/Adafruit_nRF52_Bootloader.git
cd Adafruit_nRF52_Bootloader
# only download what is needed, use
# `git submodule update --init --recursive`
# to download everything
git submodule update --init
git -C lib/tinyusb submodule update --init hw/mcu/nordic/nrfx/
pip3 install --user adafruit-nrfutil
make BOARD=feather_nrf52840_express all
make BOARD=feather_nrf52840_express flash
make BOARD=feather_nrf52840_express flash-sd
Updating Old Bootloaders and Restoring the SoftDevice
In some cases the bootloader may be too old to even mount on startup.
Enter the bootloader mode (usually by double tapping the reset button for
nRF52840 based boards) and check the INFO_UF2.TXT for bootloader information.
If the version is less than 0.4.0 then one can use the
Adafruit_nRF52_Bootloader
tool to update.
Until and including RIOT Release 2025.01, the SoftDevice on feather-nrf52840 and
feather-nrf52840-sense boards got erased when flashing RIOT. To restore the
ability of using i.a. Arduino and CircuitPython, the SoftDevice has to be
flashed again. This can be done in the same way as updating the bootloader.
Sometimes the process has to be done twice until the SoftDevice is successfully
restored.
For example, one can run the following if arm-none-eabi-gcc and
adafruit-nrfutil are installed. Make sure to select the correct board for your
application.
git clone https://github.com/adafruit/Adafruit_nRF52_Bootloader.git
cd Adafruit_nRF52_Bootloader
git submodule update --init
make BOARD=feather_nrf52840_sense SERIAL=/dev/ttyACM0 flash-dfu
Further information can be found on the Adafruit Website.