[嵌入式]STM32 Rtthread启动流程基于GNU交叉编译

STM32 Rtthread启动流程基于GNU交叉编译

Rtthread并不是直接从main函数开始启动的，而是从componets.c中通过entry函数启动的：

//需要在board.c中开启这个宏RT_USING_USER_MAIN

//我使用的时GNU编译器，所以入口函数在这，可以在ld命令中指定entry为入口地址，
//也可以在startup_stm32f411xe.s中指定入口地址为entry
/* Add -eentry to arm-none-eabi-gcc argument */
int entry(void)
{
    rtthread_startup();
    return 0;
}

int rtthread_startup(void)
{
    rt_hw_interrupt_disable();

    /* board level initialization
     * NOTE: please initialize heap inside board initialization.
     */
    rt_hw_board_init();

    /* show RT-Thread version */
    rt_show_version();

    /* timer system initialization */
    rt_system_timer_init();

    /* scheduler system initialization */
    rt_system_scheduler_init();

    /* create init_thread */
    rt_application_init();

    /* timer thread initialization */
    rt_system_timer_thread_init();

    /* idle thread initialization */
    rt_thread_idle_init();

    /* start scheduler */
    rt_system_scheduler_start();

    /* never reach here */
    return 0;
}

//rt_hw_board_init函数在board.c中定义，主要功能是做硬件初始化
void rt_hw_board_init()
{
    USART1_Config(115200);//串口初始化
    KEY_Init();//按键初始化
    LED_init();//LED初始化
    /* System Clock Update */
    //该函数在system_stm32f4xx.c中定义，主要功能是获取SystemCoreClock 的值。
    SystemCoreClockUpdate();
    
    /* System Tick Configuration */
    _SysTick_Config(SystemCoreClock / RT_TICK_PER_SECOND);//RT_TICK_PER_SECOND 1000

    /* Call components board initial (use INIT_BOARD_EXPORT()) */
#ifdef RT_USING_COMPONENTS_INIT
    rt_components_board_init();
#endif

#if defined(RT_USING_CONSOLE) && defined(RT_USING_DEVICE)
    //rt_console_set_device(RT_CONSOLE_DEVICE_NAME);
#endif

#if defined(RT_USING_USER_MAIN) && defined(RT_USING_HEAP) //初始化堆
   rt_system_heap_init(rt_heap_begin_get(), rt_heap_end_get());
#endif

}

static uint32_t _SysTick_Config(rt_uint32_t ticks)
{
    if ((ticks - 1) > 0xFFFFFF)
    {
        return 1;
    }
    
    _SYSTICK_LOAD = ticks - 1; //RELOAD VALUE
    _SYSTICK_PRI = 0xFF;       //PRIORITY OF SYSTICK LOW
    _SYSTICK_VAL  = 0;         //CLEAR CURRENT VALUE OF SYSTICK COUNT
    //systick ctrl寄存器bit2 为1时使用AHB作为systic频率，不分频
    _SYSTICK_CTRL = 0x07;      //0x07 BIT2 ==1 使用AHB，0：使用内部时钟源，AHB/8

    return 0;
}
//rt_components_board_init函数会初始化INIT_EXPORT(fn, level) 宏包起来的函数
//可以看看这篇文章：https://blog.csdn.net/qq_42370291/article/details/103639349
void rt_components_board_init(void)
{
#if RT_DEBUG_INIT //开了RT_DEBUG_INIT 将会打印出被调用的初始化的函数
    int result;
    const struct rt_init_desc *desc;
    for (desc = &__rt_init_desc_rti_board_start; desc < &__rt_init_desc_rti_board_end; desc ++)
    {
        rt_kprintf("initialize %s", desc->fn_name);
        result = desc->fn();
        rt_kprintf(":%d done\n", result);
    }
#else
    volatile const init_fn_t *fn_ptr;

    for (fn_ptr = &__rt_init_rti_board_start; fn_ptr < &__rt_init_rti_board_end; fn_ptr++)
    {
        (*fn_ptr)();
    }
#endif
}

在startup_stm32f411xe.s中指定入口地址为entry

/* Call the application's entry point.*/
  bl  entry //这里之前是main
  bx  lr