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use core::convert::Infallible;
use core::ptr::{read_volatile, write_volatile};
use embedded_hal::serial::nb::{Read, Write};
pub struct Ns16550a {
base: usize,
shift: usize,
}
impl Ns16550a {
pub fn new(base: usize, shift: usize ) -> Self {
Self { base, shift }
}
}
impl embedded_hal::serial::ErrorType for Ns16550a {
type Error = Infallible;
}
impl Read<u8> for Ns16550a {
fn read(&mut self) -> nb::Result<u8, Self::Error> {
let pending =
unsafe { read_volatile((self.base + (offsets::LSR << self.shift)) as *const u8) }
& masks::DR;
if pending != 0 {
let word =
unsafe { read_volatile((self.base + (offsets::RBR << self.shift)) as *const u8) };
Ok(word)
} else {
Err(nb::Error::WouldBlock)
}
}
}
impl Write<u8> for Ns16550a {
fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
unsafe { write_volatile((self.base + (offsets::THR << self.shift)) as *mut u8, word) };
Ok(())
}
fn flush(&mut self) -> nb::Result<(), Self::Error> {
let pending =
unsafe { read_volatile((self.base + (offsets::LSR << self.shift)) as *const u8) }
& masks::THRE;
if pending != 0 {
Ok(())
} else {
Err(nb::Error::WouldBlock)
}
}
}
mod offsets {
pub const RBR: usize = 0x0;
pub const THR: usize = 0x0;
pub const IER: usize = 0x1;
pub const FCR: usize = 0x2;
pub const LCR: usize = 0x3;
pub const MCR: usize = 0x4;
pub const LSR: usize = 0x5;
pub const DLL: usize = 0x0;
pub const DLH: usize = 0x1;
}
mod masks {
pub const THRE: u8 = 1 << 5;
pub const DR: u8 = 1;
}