Integration method of C++ and RTOS in embedded systems

There are three methods for integrating C and RTOS in embedded systems: Interrupt-free method: C code is separated from RTOS scheduling and gives up real-time performance. Cooperative multitasking: C tasks interact with the RTOS, incurring context switching overhead. Preemptive multitasking: C tasks are scheduled by the RTOS, providing optimal real-time performance.

Integration of C and RTOS in embedded systems

Integration of C and real-time operating system (RTOS) in embedded systems For Improving performance and reliability is critical. This article introduces several methods of integrating C and RTOS and provides a practical case.

Method:

• Interrupt-free method: C code runs outside of the RTOS schedule and does not handle interrupts. This method is simple to implement, but gives up the real-time nature of RTOS.
• Cooperative multitasking: C tasks interact with RTOS through POSIX threads or RTOS API. This approach can take advantage of RTOS capabilities, but there is context switching overhead.
• Preemptive multitasking: C tasks are scheduled and preempted by the RTOS, providing the best real-time performance, but will bring additional complexity.

Practical case:

Consider an embedded system that needs to display a message on an LED while responding to a button press. The following example of writing C code using FreeRTOS and cooperative multitasking:

#include "FreeRTOS.h"
#include "task.h"

// 任务函数：显示消息
static void displayTask(void *pvParameters) {
    while (true) {
        // 显示消息
        printf("Hello, world!\n");

        // 等待下一次调用
        vTaskSuspend(NULL);
    }
}

// 任务函数：处理按钮按下
static void buttonTask(void *pvParameters) {
    while (true) {
        // 轮询按钮
        if (isButtonDown()) {
            // 通知显示任务显示消息
            xTaskResumeFromISR(displayTask);
        }

        // 延时
        vTaskDelay(100);
    }
}

int main() {
    // 创建显示任务
    xTaskCreate(displayTask, "Display", 256, NULL, 1, NULL);

    // 创建按钮任务
    xTaskCreate(buttonTask, "Button", 128, NULL, 2, NULL);

    // 启动任务调度器
    vTaskStartScheduler();

    return 0;
}

Note:

• uses the FreeRTOS vTaskSuspend() and vTaskResumeFromISR() functions, They interact with tasks in a cooperative multitasking environment.
• The POSIX printf() function is used, which requires standard library support to be enabled on FreeRTOS.
• The main() function is usually redundant on embedded systems, but helps demonstrate how to set up a task.

The above is the detailed content of Integration method of C++ and RTOS in embedded systems. For more information, please follow other related articles on the PHP Chinese website!