MicroEJ Core Engine Abstraction Layer implementation for Zephyr OS.

This module implements the LLMJVM Low Level API for MicroEJ Platforms connected to a Board Support Package based on Zephyr OS.

See these sections of the MicroEJ documentation for a description of the LLMJVM functions:

• LLMJVM: MicroEJ Core Engine
• MicroEJ Core Engine: Implementation

1. Install the src directory in your Board Support Package. It can be automatically downloaded using the following command line:

    svn export --force https://github.com/MicroEJ/AbstractionLayer-Core-Zephyr/trunk/src/main/c/src [path_to_bsp_directory]

2. The LLMJVM_IMPL_scheduleRequest schedule request function in LLMJVM_ZephyrOS.c uses a software timer. In order to correctly schedule MicroEJ threads, check the following elements in the Zephyr OS configuration file:

   • CONFIG_SYS_CLOCK_TICKS_PER_SEC: can depend on the application, if it needs a 1 ms precision then the tick rate would be 1000 Hz, the recommended value is between 100 Hz and 1000 Hz (see Zephyr Kernel Timing page for more details)

3. The LLMJVM_IMPL_getTimeNanos function in LLMJVM_ZephyrOS.c gets the current timestamp in nanoseconds. Not all hardware have 64 bit counters. This function returns a timestamp with a resolution depending on CONFIG_SYS_CLOCK_TICKS_PER_SEC if CONFIG_TIMER_HAS_64BIT_CYCLE_COUNTER is not set. In this case, it is strongly recommended to update your implementation using the APIs of your target HAL drivers to get a better precision.

Note: the application time is retrieved using the Zephyr Kernel API k_uptime_get(). While this function returns time in milliseconds, it does not mean it has millisecond resolution. The actual resolution depends on CONFIG_SYS_CLOCK_TICKS_PER_SEC config option.

None.

This Abstraction Layer implementation can be validated in the target Board Support Package using the MicroEJ Core Validation VEE Port Qualification Tools project.

Here is a non-exhaustive list of tested environments:

• Hardware
  • STMicroelectronics NUCLEO-H563ZI
• Compilers / Build environments:
  • ZEPHYR SDK 0.16.5
• Zephyr OS v3.6.0

The implementation is MISRA-compliant (MISRA C:2012). It has been verified with Cppcheck v2.10.0. Here is the list of deviations:

Copy/paste source code in your VEE Port BSP project or add the following line to your VEE Port configuration module.ivy:

<dependency org="com.microej.clibrary.llimpl" name="mjvm-zephyros" rev="..."/>

Note: Run the MicroEJ Core Validation VEE Port Qualification Tools project to validate code integration in your environment.

• MicroEJ Architecture 8.x or higher.
• Zephyr OS 3.6.0 or higher.

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Copyright 2021-2024 MicroEJ Corp. All rights reserved. Use of this source code is governed by a BSD-style license that can be found with this software.