OTUS_RXBUFSZ
usbd_setup_xfer(xfer, sc->data_rx_pipe, data, data->buf, OTUS_RXBUFSZ,
OTUS_RXBUFSZ, USBD_SHORT_XFER_OK | USBD_NO_COPY,
data->buf = usbd_alloc_buffer(data->xfer, OTUS_RXBUFSZ);