CMSIS Support

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 table describes CMSIS-RTOS v2 APIs. For more details about the APIs, see the API reference.

Table 1 CMSIS-RTOS v2 APIs

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-specific 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) {
 // Initialize the system.
  MySystemInit();
  // ...

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