Overview

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

Usage

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.

Requirements

None.

Validation

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

MISRA Compliance

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

Deviation	Category	Action	Justification
Rule 2.1	Required	Flagged	A deviation from this rule is necessary as LLMJVM_IMPL_ functions are called from the VM
Rule 5.5	Required	Ignored	A deviation from this rule is necessary as macros are used to map VM symbols to LLMJVM_IMPL_ functions

Usage

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.

Dependencies

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

Source

N/A.

Restrictions

None.

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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.