I'm using an nRF52840 Feather Express board and would like to flash my own custom bootloader to it. I would like to do this via UF2 so I don't have JTAG new devices that haven't been flashed with the bootloader yet.
I tried the following script on my own bootloader (this bootloader is largely based on Nordic's secure_bootloader example project in nRF5 SDK v17.1.0 with very little changes):
Code: Select all
uf2conv.py nrf52840_xxaa_s140.hex -c -f 0xADA52840
This produces a flash.uf2 file, but when I transfer it to the Feather Express it will not update. The Feather Express is running v0.7.0 of Adafruit's bootloader.
How can I create a .uf2 file to update to my own bootloader?