Macro uart_pin_macro 

macro_rules! uart_pin_macro {
    ($UARTn:ident,
        cts: [$(($($ctsgpio: ident)::*, $ctsaf: ident)),*],
        // dcd: [() $(, ($($dcdgpio: ident)::*, $dcdaf: ident))*],
        // dsr: [() $(, ($($dsrgpio: ident)::*, $dsraf: ident))*],
        // dtr: [() $(, ($($dtrgpio: ident)::*, $dtraf: ident))*],
        // ri: [() $(, ($($rigpio: ident)::*, $riaf: ident))*],
        rts: [$(($($rtsgpio: ident)::*, $rtsaf: ident)),*],
        rx: [$(($($rxgpio: ident)::*, $rxaf: ident)),*],
        tx: [$(($($txgpio: ident)::*, $txaf: ident)),*],
    ) => { ... };
}

! An internal macro to help define all the different pin typestates