UCOSII的任务调度,led_task是LED0和LED1每隔500ms翻转一次,beep_task在没有收到删除请求的时候是隔一段时间蜂鸣器鸣叫一次，key_task是进行按键扫描。-UCOSII task scheduling, led_task is LED0 and LED1 every 500ms flip once, beep_task in the absence of a request to delete the request is separated by a perio