USBVC_BUF_EMPTY
bufgrp->buf_filling->status = USBVC_BUF_EMPTY;
case USBVC_BUF_EMPTY:
if (usbvc_buf->status == USBVC_BUF_EMPTY) {
usbvc_buf->status = USBVC_BUF_EMPTY;
usbvc_buf->status = USBVC_BUF_EMPTY;