First of all, lets flash Adafruit’s NRF52 bootloader for easier future flashing
My J-Link was “Broken. No longer used” - or so the JLink tools said (AKA bought from e-bay). So I had to go to openocd).
Connect the J-Link (or any SWD capable debugger supported by openocd - even an FT232 breakout will do) to the target - I have a Bluefruit by Adafruit.
pip3 install --user intelhex
cd Adafruit_nRF52_Bootloader
git clone https://github.com/adafruit/Adafruit_nRF52_Bootloader
git submodule update --init
make BOARD=feather_nrf52832 all
FIRMWARE=lib/softdevice/s132_nrf52_6.1.1/s132_nrf52_6.1.1_softdevice.hex
sudo openocd -f board/nordic_nrf52_dk.cfg -c init -c “reset init” -c halt -c “nrf5 mass_erase” -c “program $FIRMWARE verify” -c reset -c exit
FIRMWARE=_build/build-feather_nrf52832/feather_nrf52832_bootloader-0.3.2-28-g79a6a0c-nosd.hex
sudo openocd -f board/nordic_nrf52_dk.cfg -c init -c “reset init” -c halt -c “program $FIRMWARE verify” -c reset -c exi
💡**NOTE**: `nrf5` command was missing from my package manager’s `openocd` and I needed to install the git version!
Now the bootloader should be flash and we’re able to flash over serial from now on! Lets flash micropython (I advise not flashing master but a stable tag)