Program a SAMD21 with OpenOCD and a JLINK

openocd-samd21.cfg

# Program a SAMD21 part with a bootloader using a JLINK / J-LINK
# 0a. Wire up your device with SWD & SWC pins to JLINK
# 0b. Also wire up Gnd and Power to Gnd & VTref on JLINK
# 0c. And separately supply power to device 
# 0d. Iif you don't have openocd installed, then "brew install openocd"
#
# 1. Put this file in a directory
# 2. Get a samd21 bootloader file.bin and put it in this directory renamed as "bootloader.bin"
# 3. Unplug and replug in the JLINK (to reset it)
# 4. Then do "openocd -f ./openocd-sams21.cfg" and stand back

source [find interface/jlink.cfg]
transport select swd
source [find target/at91samdXX.cfg]
init
reset
halt
program bootloader.bin verify reset
shutdown

this specific script from https://hackaday.io/page/5997-programming-a-samd-bootloader-using-jlink-linux

but also see:

• https://gist.github.com/todbot/6b8da4bed3545313ae976be6be7ffc40
• https://github.com/todbot/samd21-programming-notes

Another way. Uses load_image instead of program. Put this in openocd-samd21-way2.cfg and do openocd -f ./openocd-samd21-way2.cfg:

source [find interface/jlink.cfg]
transport select swd
source [find target/at91samdXX.cfg]
init
reset
halt
load_image bootloader.bin 0
verify_image bootloader.bin 0 bin
reset run
shutdown

Also, if you get the error:

Error: SAMD: NVM lock error

then add this line after the halt line:

at91samd bootloader 0