function "usbh_msc_status()" can't check the connected usb hardware .

int main(void)
{ -----. . .

-----retv = finit ("U:");

-----while(1)

-----{

----------retv = usbh_engine(0);

----------con = usbh_msc_status(0,0);

----------if(con==1)

----------{

---------------. . .

----------}

-----}

}

The program is as above.

If a usb mass storage device is connected before power up, then "con=1" after the program

is executed. At this time, "usbh_msc_status" can check the connected mass storage device.

But if no usb mass storage device is connected before power up, then con=0 forever,

whatever a usb mass storage device is connected or not.

How to find the usb device immediately, as soon as the usb mass storage device is connected.