USB_CDC_CTRL_RTS
val = USB_CDC_CTRL_DTR | USB_CDC_CTRL_RTS;
(acm->ctrlout & USB_CDC_CTRL_RTS ? TIOCM_RTS : 0) |
(set & TIOCM_RTS ? USB_CDC_CTRL_RTS : 0);
(clear & TIOCM_RTS ? USB_CDC_CTRL_RTS : 0);
val |= USB_CDC_CTRL_RTS;