acm_set_control
acm_set_control(acm, acm->ctrlout = newctrl);
acm_set_control(acm, USB_CDC_CTRL_DTR | USB_CDC_CTRL_RTS);
res = acm_set_control(acm, val);
acm_set_control(acm, USB_CDC_CTRL_DTR | USB_CDC_CTRL_RTS);
return acm_set_control(acm, acm->ctrlout = newctrl);