由于原RMK固件移除了SoftDevice，在刷入ZMK固件之前，必须先恢复SoftDevice：
- 先用SoftDevice恢复包刷入，地址：bootloader/s140_restore.uf2
- Recovery模式进入方法：双击RESET键进入bootloader
- 刷入zmk固件：使用UF2拖拽方式刷入
注意顺序：先SoftDevice → 后ZMK固件
Download the bootloader for nRF52840 from:
- Official repository: https://github.com/joric/nrfmicro/wiki/Bootloader
- This bootloader is compatible with nRF52840-based keyboards using ZMK firmware
These commands extract the SoftDevice (s140) from the bootloader HEX file and convert it to UF2 format for flashing:
# Convert HEX to binary
arm-none-eabi-objcopy -I ihex -O binary pca10056_bootloader-0.2.11_s140_6.1.1.hex full_flash.bin
# Extract SoftDevice section
# Skip bootloader (4096 bytes, start address 0x1000)
# Count matches SoftDevice size (151016 bytes, end address: 0x25DE7 )
dd if=full_flash.bin of=s140_sd_only.bin bs=1 skip=4096 count=151016
# method 1: generate hex file, flashing with nrfutil or nrf connect
arm-none-eabi-objcopy -O ihex -I binary s140_sd_only.bin s140_sd_only.hex
arm-none-eabi-objcopy --change-address 0x1000 s140_sd_only.hex s140_sd_only.hex
# method 2: generate uf2 , flash by uf2 bootloader
# Convert bin content to UF2 format with start address for flashing
python3 uf2conv.py s140_sd_only.bin -f 0xada52840 -b 0x1000 -c -o s140_restore.uf2nRF Connect for Desktop's Programer is very useful for getting sd address and size from bootloader hex file.
Command to extract SoftDevice (s130) section:
# Skip bootloader (4096 bytes)
dd if=full_flash.bin of=s132_sd_only.bin bs=1 skip=4096 count=155648