UMODEM_BULK_WR
[UMODEM_BULK_WR] = {
usbd_transfer_start(sc->sc_xfer[UMODEM_BULK_WR]);
usbd_transfer_stop(sc->sc_xfer[UMODEM_BULK_WR]);
usbd_xfer_set_stall(sc->sc_xfer[UMODEM_BULK_WR]);