Standard Libraries

CMSIS

Basic Concepts

The Cortex Microcontroller Software Interface Standard (CMSIS) is a vendor-independent hardware abstraction layer for microcontrollers based on Arm Cortex processors. Of the CMSIS components, the Real Time Operating System (RTOS) defines a set of universal and standardized APIs to reduce the dependency of application developers on specific RTOS and facilitate software porting and reuse. The CMSIS provides CMSIS-RTOS v1 and CMSIS-RTOS v2. The OpenHarmony LiteOS-M supports only the implementation of CMSIS-RTOS v2.

Development Guidelines

Available APIs

The following tables describe CMSIS-RTOS v2 APIs. For more details about the APIs, see the API reference.

Table 1 APIs for obtaining kernel information and controlling the kernel

Table 2 APIs for thread management

Table 3 APIs for thread flags

Table 4 APIs for event flags

Table 5 General wait functions

Table 6 APIs for timer management

Table 7 APIs for mutex management

Table 8 APIs for semaphore management

Table 9 APIs for memory pool management

Table 10 APIs for message queues

How to Develop

The CMSIS-RTOS v2 component can be provided as a library (shown in the figure) or source code. By adding the CMSIS-RTOS v2 component (typically configuration files), you can implement RTOS capabilities on CMSIS-based applications. You only need to include the cmsis_os2.h header file. RTOS APIs can then be called to process RTOS kernel-related events. You do not need to recompile the source code when the kernel is replaced.

The RTOS object control block definition needs to be called for static object allocation. The implementation header file (os_xx.h in the following figure) provides access to such control block definitions. In the OpenHarmony LiteOS-M kernel, the header files whose names start with los_ provide the definitions of the kernel.

Development Example

#include ...
#include "cmsis_os2.h"

/*----------------------------------------------------------------------------
 * Application main thread
 *---------------------------------------------------------------------------*/
void app_main (void *argument) {
  // ...
  for (;;) {}
}

int main (void) {
  // System initialization
  MySystemInit();
  // ...

  osKernelInitialize();                // Initialize CMSIS-RTOS.
  osThreadNew(app_main, NULL, NULL);   // Create the main thread of the application.
  osKernelStart();                     // Start to execute the thread.
  for (;;) {}
}

POSIX

Basic Concepts

The OpenHarmony kernel uses the musl libc library and self-developed APIs and supports the Portable Operating System Interface (POSIX). You can develop components and applications working on the kernel based on the POSIX.

Development Guidelines

Available APIs

Table 11 APIs for process management

Table 12 APIs for file system management

Table 13 APIs for time management

Table 14 APIs for util

Table 15 APIs for math operations

Table 16 APIs for I/O operations

Table 17 APIs for network

Table 18 APIs for memory management

Table 19 APIs for IPC

Error Codes

The table below lists common error codes.

Development Example

Example:

Creates a thread, transfers the information in the parent thread to the child thread, and prints the transferred information and the thread ID in the child thread.

The sample code can be compiled and verified in ./kernel/liteos_m/testsuites/src/osTest.c. The DemoForTest function is called in TestTaskEntry.

#include <stdio.h>
#include <pthread.h>

pthread_t ntid;

void *ThreadFn(void *arg)
{
    pthread_t tid;
    while(1) {
        tid = pthread_self();
        printf("\n++++++++++++++  %s  %s  tid = %d ++++++++++++++\n", (char*)arg, __FUNCTION__, tid);
    }
    return ((void *)0);
}

void DemoForTest()
{
    int err;
    char* str = "Hello world";
    err = pthread_create(&ntid, NULL, ThreadFn, (void*)str);
    if(err != 0) {
        printf("can't create thread\n");
    }
}

The execution result of DemoForTest is as follows:

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++

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