linux下ttyUSB0设备开机、关闭、重起的自动检测c代码

linux下ttyUSB0设备开机、关闭、重起的自动检测c代码


#include <sys/time.h>
#include <time.h>
bool try2connect_ttyusb(void)
{
    int file;
    struct timeval time_ticks;

    int past_closed = 0;
    int time_closed = 0;
    int time_closed_tmp,time_closed_tmp_pre;
    
    for(;;)
    {
        gettimeofday(&time_ticks,NULL);
        if(time_ticks.tv_usec < 1000)break;//等待近似0ms的开始
        file = open(DeviceName, O_RDWR | O_NOCTTY | O_NDELAY);
        if(file > 0)
        {
            close(file);
        }else return true;//有可能已经等待1s了,已经完成了重启,所以可以退出
    }
    time_closed_tmp_pre = 0;
    for(;;)
    {
        file = open(DeviceName, O_RDWR | O_NOCTTY | O_NDELAY);
        if(file > 0)
        {
            close(file);
            if(past_closed)
            {
                fprintf(stderr,"\n%d个100ms过去了##",time_closed);
                break;
            }
        }else past_closed = 1;
        //gliethttp_20080327
        gettimeofday(&time_ticks,NULL);
        time_closed_tmp = time_ticks.tv_usec / (100*1000);
        if(time_closed_tmp != time_closed_tmp_pre)
        {
            if(time_closed++ > 50)
            {
                fprintf(stderr,"\ntime out\n");
                break;
            }
            
#if 0
            if(file < 0)fprintf(stderr,"\nNO");
            else
            {
                fprintf(stderr,"\nYES");
            }
#endif
            time_closed_tmp_pre = time_closed_tmp;
        }
    }
    return (past_closed && (file > 0));
}