Targeting Zephyr

Zephyr is a real-time OS kernel used as an OS target by EtcPal. To use EtcPal with Zephyr, you must set the ETCPAL_OS_TARGET variable to zephyr.

set(ETCPAL_OS_TARGET zephyr CACHE STRING "The OS target for EtcPal")

Building for Zephyr requires a properly set up Zephyr project which calls:

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})

prior to running the cmake for EtcPal.

Zephyr is highly configurable and is not compatible with EtcPal in its default configuration. Some changes are required in order to make them compatible:

1. EtcPal expects preemptive timeslicing meaning that threads of lower or equal priority should not be able to starve out higher or equal priority threads. However, by default, Zephyr does not implement timeslicing and only dedicates specific priorities to be preemptive. In order for threads to behave the way EtcPal expects, their priorities must be within this preemptive range and timeslicing must be enabled in KConfig. Read more about this here: Zephyr Scheduling
2. EtcPal threads and queues are dynamically allocated. Zephyr by default only allows for static allocation. To use EtcPal threads and queues, dynamic threads and a malloc implementation must both be enabled in KConfig.