scripts: Add support for passing daparg argument to pyocd commands

pyocd occasionally throws USB timeout exceptions when running in
VirtualBox, and recently added a command-line option to limit the USB
packet count as a workaround. Introduce an environment variable
PYOCD_DAPARG so Zephyr can pass the argument to pyocd. For example:

$ make BOARD=frdm_k64f PYOCD_DAPARG='limit_packets=True' flash

This workound comes with a performance penalty when flashing and
debugging with pyocd, so it should only be used when running pyocd in

Signed-off-by: Maureen Helm <>
1 file changed