#include <RTL.h>
#include <rl_usb.h>
int main (void) {
usbd_init (); // USB Device Initialize
usbd_connect (__TRUE); // USB Device Connect
while (1) { // Loop forever
..
usbd_vcom_serial2usb(); // Send data from serial COM port to USB CDC Device
usbd_vcom_chkserstate(); // Check serial connection
usbd_vcom_usb2serial(); // Send data from USB CDC Device to serial COM port
..
}
}