DK programming and serial debugging

Flash without erasing bonds

Use J-Link Commander's loadfile command for normal development:

JLinkExe -device NRF52840_XXAA -if SWD -speed 4000 -autoconnect 1

At the J-Link> prompt:

loadfile /absolute/path/to/zmk.hex
r
g
exit

Typical images are:

.zmk/build/thinkpad_t430/zephyr/zmk.hex
.zmk/build/thinkpad_t470/zephyr/zmk.hex

Tests on the T470 DK showed that loadfile left the 32 KiB settings partition unchanged and preserved its BLE bond.

Do not copy a normal update to /Volumes/JLINK. The DK mass-storage programmer erases settings even when the HEX file does not overlap that partition. Use it only for an intentional clean flash:

cp path/to/zmk.hex /Volumes/JLINK/zmk.hex
sync

A clean flash removes BLE profiles and requires pairing each host again.

Inspect settings

DK settings occupy 0xF8000–0xFFFFF. To check suspected data loss, halt the target and save the partition before and after flashing:

savebin tmp/thinkpad-settings-before.bin 0xF8000 0x8000
savebin tmp/thinkpad-settings-after.bin 0xF8000 0x8000

Compare the files with cmp or SHA-256. Run r and g after diagnostic reads.

Read serial logs

UART0 logs use the DK interface USB serial port at 115200 baud. On macOS:

brew install tio
find /dev -maxdepth 1 -name 'cu.usbmodem*' -print
tio -b 115200 /dev/cu.usbmodemXXXX

Replace the example device with the path reported by find. Connect the DK's second USB port when testing USB keyboard and pointer output.

Custom Revision A boards use a different process. See Revision A programming.