# lib.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/embedded-hal-1.0.0-alpha.1/src/lib.rs`.
Keywords: rust, rustlang, rust-lang

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    //! A Hardware Abstraction Layer (HAL) for embedded systems
    //!
    //! **NOTE** This HAL is still is active development. Expect the traits presented here to be
    //! tweaked, split or be replaced wholesale before being stabilized, i.e. before hitting the 1.0.0
    //! release.
    //!
    //! # Design goals
    //!
    //! The HAL
    //!
    //! - Must *erase* device specific details. Neither register, register blocks or magic values should
    //! appear in the API.
    //!
    //! - Must be generic *within* a device and *across* devices. The API to use a serial interface must
    //! be the same regardless of whether the implementation uses the USART1 or UART4 peripheral of a
    //! device or the UART0 peripheral of another device.
    //!
    //! - Where possible must *not* be tied to a specific asynchronous model. The API should be usable
    //! in blocking mode, with the `futures` model, with an async/await model or with a callback model.
    //! (cf. the [`nb`] crate)
    //!
    //! - Must be minimal, and thus easy to implement and zero cost, yet highly composable. People that
    //! want higher level abstraction should *prefer to use this HAL* rather than *re-implement*
    //! register manipulation code.
    //!
    //! - Serve as a foundation for building an ecosystem of platform agnostic drivers. Here driver
    //! means a library crate that lets a target platform interface an external device like a digital
    //! sensor or a wireless transceiver. The advantage of this system is that by writing the driver as
    //! a generic library on top of `embedded-hal` driver authors can support any number of target
    //! platforms (e.g. Cortex-M microcontrollers, AVR microcontrollers, embedded Linux, etc.). The
    //! advantage for application developers is that by adopting `embedded-hal` they can unlock all
    //! these drivers for their platform.
    //!
    //! # Out of scope
    //!
    //! - Initialization and configuration stuff like "ensure this serial interface and that SPI
    //! interface are not using the same pins". The HAL will focus on *doing I/O*.
    //!
    //! # Reference implementation
    //!
    //! The [`stm32f30x-hal`] crate contains a reference implementation of this HAL.
    //!
    //! [`stm32f30x-hal`]: https://crates.io/crates/stm32f30x-hal/0.1.0
    //!
    //! # Platform agnostic drivers
    //!
    //! You can find platform agnostic drivers built on top of `embedded-hal` on crates.io by [searching
    //! for the *embedded-hal* keyword](https://crates.io/keywords/embedded-hal).
    //!
    //! If you are writing a platform agnostic driver yourself you are highly encouraged to [add the
    //! embedded-hal keyword](https://doc.rust-lang.org/cargo/reference/manifest.html#package-metadata)
    //! to your crate before publishing it!
    //!
    //! # Detailed design
    //!
    //! ## Traits
    //!
    //! The HAL is specified as traits to allow generic programming. These traits make use of the
    //! [`nb`][] crate (*please go read that crate documentation before continuing*) to abstract over
    //! the asynchronous model and to also provide a blocking operation mode.
    //!
    //! [`nb`]: https://crates.io/crates/nb
    //!
    //! Here's how a HAL trait may look like:
    //!
    //! ```
    //! extern crate nb;
    //!
    //! /// A serial interface
    //! pub trait Serial {
    //!     /// Error type associated to this serial interface
    //!     type Error;
    //!
    //!     /// Reads a single byte
    //!     fn try_read(&mut self) -> nb::Result<u8, Self::Error>;
    //!
    //!     /// Writes a single byte
    //!     fn try_write(&mut self, byte: u8) -> nb::Result<(), Self::Error>;
    //! }
    //! ```
    //!
    //! The `nb::Result` enum is used to add a [`WouldBlock`] variant to the errors
    //! of the serial interface. As explained in the documentation of the `nb` crate this single API,
    //! when paired with the macros in the `nb` crate, can operate in a blocking manner, or in a
    //! non-blocking manner compatible with `futures` and with the `await!` operator.
    //!
    //! [`WouldBlock`]: https://docs.rs/nb/0.1.0/nb/enum.Error.html
    //!
    //! Some traits, like the one shown below, may expose possibly blocking APIs that can't fail. In
    //! those cases `nb::Result<_, Infallible>` is used.
    //!
    //! ```
    //! extern crate nb;
    //!
    //! # use std as core;
    //! use ::core::convert::Infallible;
    //!
    //! /// A count down timer
    //! pub trait CountDown {
    //!     // ..
    //!
    //!     /// "waits" until the count down is over
    //!     fn try_wait(&mut self) -> nb::Result<(), Infallible>;
    //! }
    //!
    //! # fn main() {}
    //! ```
    //!
    //! ## Suggested implementation
    //!
    //! The HAL traits should be implemented for device crates generated via [`svd2rust`] to maximize
    //! code reuse.
    //!
    //! [`svd2rust`]: https://crates.io/crates/svd2rust
    //!
    //! Shown below is an implementation of some of the HAL traits for the [`stm32f30x`] crate. This
    //! single implementation will work for *any* microcontroller in the STM32F30x family.
    //!
    //! [`stm32f3`]: https://crates.io/crates/stm32f3
    //!
    //! ```
    //! // crate: stm32f3xx-hal
    //! // An implementation of the `embedded-hal` traits for STM32F3xx microcontrollers
    //!
    //! extern crate embedded_hal as hal;
    //! extern crate nb;
    //!
    //! // device crate
    //! extern crate stm32f3;
    //!
    //! use stm32f3::stm32f303::USART1;
    //!
    //! /// A serial interface
    //! // NOTE generic over the USART peripheral
    //! pub struct Serial<USART> { usart: USART }
    //!
    //! // convenience type alias
    //! pub type Serial1 = Serial<USART1>;
    //!
    //! /// Serial interface error
    //! pub enum Error {
    //!     /// Buffer overrun
    //!     Overrun,
    //!     // omitted: other error variants
    //! }
    //!
    //! impl hal::serial::Read<u8> for Serial<USART1> {
    //!     type Error = Error;
    //!
    //!     fn try_read(&mut self) -> nb::Result<u8, Error> {
    //!         // read the status register
    //!         let isr = self.usart.isr.read();
    //!
    //!         if isr.ore().bit_is_set() {
    //!             // Error: Buffer overrun
    //!             Err(nb::Error::Other(Error::Overrun))
    //!         }
    //!         // omitted: checks for other errors
    //!         else if isr.rxne().bit_is_set() {
    //!             // Data available: read the data register
    //!             Ok(self.usart.rdr.read().bits() as u8)
    //!         } else {
    //!             // No data available yet
    //!             Err(nb::Error::WouldBlock)
    //!         }
    //!     }
    //! }
    //!
    //! impl hal::serial::Write<u8> for Serial<USART1> {
    //!     type Error = Error;
    //!
    //!     fn try_write(&mut self, byte: u8) -> nb::Result<(), Error> {
    //!         // Similar to the `try_read` implementation
    //!         # Ok(())
    //!     }
    //!
    //!     fn try_flush(&mut self) -> nb::Result<(), Error> {
    //!         // Similar to the `try_read` implementation
    //!         # Ok(())
    //!     }
    //! }
    //!
    //! # fn main() {}
    //! ```
    //!
    //! ## Intended usage
    //!
    //! Thanks to the [`nb`] crate the HAL API can be used in a blocking manner,
    //! with `futures` or with the `await` operator using the [`block!`],
    //! [`try_nb!`] and [`await!`] macros respectively.
    //!
    //! [`block!`]: https://docs.rs/nb/0.1.0/nb/macro.block.html
    //! [`try_nb!`]: https://docs.rs/nb/0.1.0/nb/index.html#how-to-use-this-crate
    //! [`await!`]: https://docs.rs/nb/0.1.0/nb/index.html#how-to-use-this-crate
    //!
    //! ### Blocking mode
    //!
    //! An example of sending a string over the serial interface in a blocking
    //! fashion:
    //!
    //! ```
    //! extern crate embedded_hal;
    //! #[macro_use(block)]
    //! extern crate nb;
    //!
    //! use stm32f30x_hal::Serial1;
    //! use embedded_hal::serial::Write;
    //!
    //! # fn main() {
    //! let mut serial: Serial1 = {
    //!     // ..
    //! #   Serial1
    //! };
    //!
    //! for byte in b"Hello, world!" {
    //!     // NOTE `block!` blocks until `serial.try_write()` completes and returns
    //!     // `Result<(), Error>`
    //!     block!(serial.try_write(*byte)).unwrap();
    //! }
    //! # }
    //!
    //! # mod stm32f30x_hal {
    //! #     use core::convert::Infallible;
    //! #     pub struct Serial1;
    //! #     impl Serial1 {
    //! #         pub fn try_write(&mut self, _: u8) -> ::nb::Result<(), Infallible> {
    //! #             Ok(())
    //! #         }
    //! #     }
    //! # }
    //! ```
    //!
    //! ### `futures`
    //!
    //! An example of running two tasks concurrently. First task: blink a LED every
    //! second. Second task: loop back data over the serial interface. The target
    //! must provide the `libstd` in order to be able to use `futures`, which is not
    //! the case for many embedded targets.
    //!
    //! ```not_run
    //! extern crate embedded_hal as hal;
    //! extern crate futures;
    //!
    //! #[macro_use(try_nb)]
    //! extern crate nb;
    //!
    //! use hal::prelude::*;
    //! use futures::{
    //!     future,
    //!     Async,
    //!     Future,
    //! };
    //! use futures::future::Loop;
    //! use stm32f30x_hal::{Led, Serial1, Timer6};
    //! use core::convert::Infallible;
    //!
    //! /// `futures` version of `CountDown.try_wait`
    //! ///
    //! /// This returns a future that must be polled to completion
    //! fn wait<T>(mut timer: T) -> impl Future<Item = T, Error = Infallible>
    //! where
    //!     T: hal::timer::CountDown,
    //! {
    //!     let mut timer = Some(timer);
    //!     future::poll_fn(move || {
    //!         try_nb!(timer.as_mut().unwrap().try_wait());
    //!
    //!         Ok(Async::Ready(timer.take().unwrap()))
    //!     })
    //! }
    //!
    //! /// `futures` version of `Serial.read`
    //! ///
    //! /// This returns a future that must be polled to completion
    //! fn read<S>(mut serial: S) -> impl Future<Item = (S, u8), Error = S::Error>
    //! where
    //!     S: hal::serial::Read<u8>,
    //! {
    //!     let mut serial = Some(serial);
    //!     future::poll_fn(move || {
    //!         let byte = try_nb!(serial.as_mut().unwrap().try_read());
    //!
    //!         Ok(Async::Ready((serial.take().unwrap(), byte)))
    //!     })
    //! }
    //!
    //! /// `futures` version of `Serial.write`
    //! ///
    //! /// This returns a future that must be polled to completion
    //! fn write<S>(mut serial: S, byte: u8) -> impl Future<Item = S, Error = S::Error>
    //! where
    //!     S: hal::serial::Write<u8>,
    //! {
    //!     let mut serial = Some(serial);
    //!     future::poll_fn(move || {
    //!         try_nb!(serial.as_mut().unwrap().try_write(byte));
    //!
    //!         Ok(Async::Ready(serial.take().unwrap()))
    //!     })
    //! }
    //!
    //! fn main() {
    //!     // HAL implementers
    //!     let timer: Timer6 = {
    //!         // ..
    //! #       Timer6
    //!     };
    //!     let serial: Serial1 = {
    //!         // ..
    //! #       Serial1
    //!     };
    //!     let led: Led = {
    //!         // ..
    //! #       Led
    //!     };
    //!
    //!     // Tasks
    //!     let mut blinky = future::loop_fn::<_, (), _, _>(
    //!         (led, timer, true),
    //!         |(mut led, mut timer, state)| {
    //!             wait(timer).map(move |timer| {
    //!                 if state {
    //!                     led.on();
    //!                 } else {
    //!                     led.off();
    //!                 }
    //!
    //!                 Loop::Continue((led, timer, !state))
    //!             })
    //!         });
    //!
    //!     let mut loopback = future::loop_fn::<_, (), _, _>(serial, |mut serial| {
    //!         read(serial).and_then(|(serial, byte)| {
    //!             write(serial, byte)
    //!         }).map(|serial| {
    //!             Loop::Continue(serial)
    //!         })
    //!     });
    //!
    //!     // Event loop
    //!     loop {
    //!         blinky.poll().unwrap(); // NOTE(unwrap) E = Infallible
    //!         loopback.poll().unwrap();
    //! #       break;
    //!     }
    //! }
    //!
    //! # mod stm32f30x_hal {
    //! #     use core::convert::Infallible;
    //! #     pub struct Timer6;
    //! #     impl ::hal::timer::CountDown for Timer6 {
    //! #         type Time = ();
    //! #
    //! #         fn try_start<T>(&mut self, _: T) -> Result<(), Infallible> where T: Into<()> {}
    //! #         fn try_wait(&mut self) -> ::nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #     }
    //! #
    //! #     pub struct Serial1;
    //! #     impl ::hal::serial::Read<u8> for Serial1 {
    //! #         type Error = Infallible;
    //! #         fn try_read(&mut self) -> ::nb::Result<u8, Infallible> { Err(::nb::Error::WouldBlock) }
    //! #     }
    //! #     impl ::hal::serial::Write<u8> for Serial1 {
    //! #         type Error = Infallible;
    //! #         fn try_flush(&mut self) -> ::nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #         fn try_write(&mut self, _: u8) -> ::nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #     }
    //! #
    //! #     pub struct Led;
    //! #     impl Led {
    //! #         pub fn off(&mut self) {}
    //! #         pub fn on(&mut self) {}
    //! #     }
    //! # }
    //! ```
    //!
    //! ### `await`
    //!
    //! Same example as above but using `await!` instead of `futures`
    //! (same remark concerning the availability of `libstd` on the
    //! target).
    //!
    //! ```not_run
    //! #![feature(generator_trait)]
    //! #![feature(generators)]
    //!
    //! extern crate embedded_hal as hal;
    //!
    //! #[macro_use(r#await)]
    //! extern crate nb;
    //!
    //! use core::ops::Generator;
    //! use core::pin::Pin;
    //!
    //! use hal::prelude::*;
    //! use stm32f30x_hal::{Led, Serial1, Timer6};
    //!
    //! fn main() {
    //!     // HAL implementers
    //!     let mut timer: Timer6 = {
    //!         // ..
    //! #       Timer6
    //!     };
    //!     let mut serial: Serial1 = {
    //!         // ..
    //! #       Serial1
    //!     };
    //!     let mut led: Led = {
    //!         // ..
    //! #       Led
    //!     };
    //!
    //!     // Tasks
    //!     let mut blinky = (move || {
    //!         let mut state = false;
    //!         loop {
    //!             // `await!` means "suspend / yield here" instead of "block until
    //!             // completion"
    //!             nb::r#await!(timer.try_wait()).unwrap(); // NOTE(unwrap) E = Infallible
    //!
    //!             state = !state;
    //!
    //!             if state {
    //!                 led.on();
    //!             } else {
    //!                 led.off();
    //!             }
    //!         }
    //!     });
    //!
    //!     let mut loopback = (move || {
    //!         loop {
    //!             let byte = nb::r#await!(serial.try_read()).unwrap();
    //!             nb::r#await!(serial.try_write(byte)).unwrap();
    //!         }
    //!     });
    //!
    //!     // Event loop
    //!     loop {
    //!         Pin::new(&mut blinky).resume();
    //!         Pin::new(&mut loopback).resume();
    //!         # break;
    //!     }
    //! }
    //!
    //! # mod stm32f30x_hal {
    //! #   use core::convert::Infallible;
    //! #   pub struct Serial1;
    //! #   impl Serial1 {
    //! #       pub fn try_read(&mut self) -> ::nb::Result<u8, Infallible> { Err(::nb::Error::WouldBlock) }
    //! #       pub fn try_write(&mut self, _: u8) -> ::nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #   }
    //! #   pub struct Timer6;
    //! #   impl Timer6 {
    //! #       pub fn try_wait(&mut self) -> ::nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #   }
    //! #   pub struct Led;
    //! #   impl Led {
    //! #       pub fn off(&mut self) {}
    //! #       pub fn on(&mut self) {}
    //! #   }
    //! # }
    //! ```
    //!
    //! ## Generic programming and higher level abstractions
    //!
    //! The core of the HAL has been kept minimal on purpose to encourage building **generic** higher
    //! level abstractions on top of it. Some higher level abstractions that pick an asynchronous model
    //! or that have blocking behavior and that are deemed useful to build other abstractions can be
    //! found in the `blocking` module and, in the future, in the `futures` and `async` modules.
    //!
    //! Some examples:
    //!
    //! **NOTE** All the functions shown below could have been written as trait
    //! methods with default implementation to allow specialization, but they have
    //! been written as functions to keep things simple.
    //!
    //! - Write a whole buffer to a serial device in blocking a fashion.
    //!
    //! ```
    //! extern crate embedded_hal as hal;
    //! #[macro_use(block)]
    //! extern crate nb;
    //!
    //! use hal::prelude::*;
    //!
    //! fn write_all<S>(serial: &mut S, buffer: &[u8]) -> Result<(), S::Error>
    //! where
    //!     S: hal::serial::Write<u8>
    //! {
    //!     for &byte in buffer {
    //!         block!(serial.try_write(byte))?;
    //!     }
    //!
    //!     Ok(())
    //! }
    //!
    //! # fn main() {}
    //! ```
    //!
    //! - Blocking serial read with timeout
    //!
    //! ```
    //! extern crate embedded_hal as hal;
    //! extern crate nb;
    //!
    //! use hal::prelude::*;
    //!
    //! enum Error<SE, TE> {
    //!     /// Serial interface error
    //!     Serial(SE),
    //!     /// Timeout error
    //!     TimedOut(TE),
    //! }
    //!
    //! fn read_with_timeout<S, T>(
    //!     serial: &mut S,
    //!     timer: &mut T,
    //!     timeout: T::Time,
    //! ) -> Result<u8, Error<S::Error, T::Error>>
    //! where
    //!     T: hal::timer::CountDown<Error = ()>,
    //!     S: hal::serial::Read<u8>,
    //! {
    //!     timer.try_start(timeout).map_err(Error::TimedOut)?;
    //!
    //!     loop {
    //!         match serial.try_read() {
    //!             // raise error
    //!             Err(nb::Error::Other(e)) => return Err(Error::Serial(e)),
    //!             Err(nb::Error::WouldBlock) => {
    //!                 // no data available yet, check the timer below
    //!             },
    //!             Ok(byte) => return Ok(byte),
    //!         }
    //!
    //!         match timer.try_wait() {
    //!             Err(nb::Error::Other(e)) => {
    //!                 // The error type specified by `timer.try_wait()` is `!`, which
    //!                 // means no error can actually occur. The Rust compiler
    //!                 // still forces us to provide this match arm, though.
    //!                 unreachable!()
    //!             },
    //!             // no timeout yet, try again
    //!             Err(nb::Error::WouldBlock) => continue,
    //!             Ok(()) => return Err(Error::TimedOut(())),
    //!         }
    //!     }
    //! }
    //!
    //! # fn main() {}
    //! ```
    //!
    //! - Asynchronous SPI transfer
    //!
    //! ```not_run
    //! #![feature(conservative_impl_trait)]
    //! #![feature(generators)]
    //! #![feature(generator_trait)]
    //!
    //! extern crate embedded_hal as hal;
    //! #[macro_use(r#await)]
    //! extern crate nb;
    //!
    //! use core::ops::Generator;
    //!
    //! /// Transfers a byte buffer of size N
    //! ///
    //! /// Returns the same byte buffer but filled with the data received from the
    //! /// slave device
    //! fn transfer<S, B>(
    //!     mut spi: S,
    //!     mut buffer: [u8; 16], // NOTE this should be generic over the size of the array
    //! ) -> impl Generator<Return = Result<(S, [u8; 16]), S::Error>, Yield = ()>
    //! where
    //!     S: hal::spi::FullDuplex<u8>,
    //! {
    //!     move || {
    //!         let n = buffer.len();
    //!         for i in 0..n {
    //!             nb::r#await!(spi.try_send(buffer[i]))?;
    //!             buffer[i] = nb::r#await!(spi.try_read())?;
    //!         }
    //!
    //!         Ok((spi, buffer))
    //!     }
    //! }
    //!
    //! # fn main() {}
    //! ```
    //!
    //! - Buffered serial interface with periodic flushing in interrupt handler
    //!
    //! ```
    //! # use std as core;
    //! extern crate embedded_hal as hal;
    //! extern crate nb;
    //!
    //! use hal::prelude::*;
    //! use ::core::convert::Infallible;
    //!
    //! fn flush<S>(serial: &mut S, cb: &mut CircularBuffer)
    //! where
    //!     S: hal::serial::Write<u8, Error = Infallible>,
    //! {
    //!     loop {
    //!         if let Some(byte) = cb.peek() {
    //!             match serial.try_write(*byte) {
    //!                 Err(nb::Error::Other(_)) => unreachable!(),
    //!                 Err(nb::Error::WouldBlock) => return,
    //!                 Ok(()) => {}, // keep flushing data
    //!             }
    //!         }
    //!
    //!         cb.pop();
    //!     }
    //! }
    //!
    //! // The stuff below could be in some other crate
    //!
    //! /// Global singleton
    //! pub struct BufferedSerial1;
    //!
    //! // NOTE private
    //! static BUFFER1: Mutex<CircularBuffer> = {
    //!     // ..
    //! #   Mutex(CircularBuffer)
    //! };
    //! static SERIAL1: Mutex<Serial1> = {
    //!     // ..
    //! #   Mutex(Serial1)
    //! };
    //!
    //! impl BufferedSerial1 {
    //!     pub fn write(&self, byte: u8) {
    //!         self.write_all(&[byte])
    //!     }
    //!
    //!     pub fn write_all(&self, bytes: &[u8]) {
    //!         let mut buffer = BUFFER1.lock();
    //!         for byte in bytes {
    //!             buffer.push(*byte).expect("buffer overrun");
    //!         }
    //!         // omitted: pend / enable interrupt_handler
    //!     }
    //! }
    //!
    //! fn interrupt_handler() {
    //!     let mut serial = SERIAL1.lock();
    //!     let mut buffer = BUFFER1.lock();
    //!
    //!     flush(&mut *serial, &mut buffer);
    //! }
    //!
    //! # struct Mutex<T>(T);
    //! # impl<T> Mutex<T> {
    //! #     fn lock(&self) -> RefMut<T> { unimplemented!() }
    //! # }
    //! # struct RefMut<'a, T>(&'a mut T) where T: 'a;
    //! # impl<'a, T> ::core::ops::Deref for RefMut<'a, T> {
    //! #     type Target = T;
    //! #     fn deref(&self) -> &T { self.0 }
    //! # }
    //! # impl<'a, T> ::core::ops::DerefMut for RefMut<'a, T> {
    //! #     fn deref_mut(&mut self) -> &mut T { self.0 }
    //! # }
    //! # struct Serial1;
    //! # impl ::hal::serial::Write<u8> for Serial1 {
    //! #   type Error = Infallible;
    //! #   fn try_write(&mut self, _: u8) -> nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! #   fn try_flush(&mut self) -> nb::Result<(), Infallible> { Err(::nb::Error::WouldBlock) }
    //! # }
    //! # struct CircularBuffer;
    //! # impl CircularBuffer {
    //! #   pub fn peek(&mut self) -> Option<&u8> { None }
    //! #   pub fn pop(&mut self) -> Option<u8> { None }
    //! #   pub fn push(&mut self, _: u8) -> Result<(), ()> { Ok(()) }
    //! # }
    //!
    //! # fn main() {}
    //! ```

    #![deny(missing_docs)]
    #![no_std]

    #[macro_use]
    extern crate nb;

    pub mod adc;
    pub mod blocking;
    pub mod capture;
    pub mod digital;
    pub mod fmt;
    pub mod prelude;
    pub mod pwm;
    pub mod qei;
    pub mod rng;
    pub mod serial;
    pub mod spi;
    pub mod timer;
    pub mod watchdog;