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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. That being said there's a part of the HAL that's currently considered unproven and is //! hidden behind an "unproven" Cargo feature. This API is even more volatile and it's exempt from //! semver rules: it can change in a non-backward compatible fashion or even disappear in between //! patch releases. //! //! # 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 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 read(&mut self) -> nb::Result<u8, Self::Error>; //! //! /// Writes a single byte //! fn 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<_, !>` is used. //! //! ``` //! #![feature(never_type)] //! //! extern crate nb; //! //! /// A count down timer //! pub trait CountDown { //! // .. //! //! /// "waits" until the count down is over //! fn wait(&mut self) -> nb::Result<(), !>; //! } //! //! # 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. //! //! [`stm32f30x`]: https://crates.io/crates/stm32f30x //! //! ``` //! // crate: stm32f30x-hal //! //! An implementation of the `embedded-hal` traits for STM32F30x microcontrollers //! //! extern crate embedded_hal as hal; //! extern crate nb; //! //! // device crate //! extern crate stm32f30x; //! //! use stm32f30x::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 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 write(&mut self, byte: u8) -> nb::Result<(), Error> { //! // Similar to the `read` implementation //! # Ok(()) //! } //! //! fn flush(&mut self) -> nb::Result<(), Error> { //! // Similar to the `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: //! //! ``` //! # #![feature(never_type)] //! 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.write()` completes and returns //! // `Result<(), Error>` //! block!(serial.write(*byte)).unwrap(); //! } //! # } //! //! # mod stm32f30x_hal { //! # pub struct Serial1; //! # impl Serial1 { //! # pub fn write(&mut self, _: u8) -> ::nb::Result<(), !> { //! # Ok(()) //! # } //! # } //! # } //! ``` //! //! ### `futures` //! //! An example of running two tasks concurrently. First task: blink an LED every //! second. Second task: loop back data over the serial interface. //! //! ``` //! #![feature(conservative_impl_trait)] //! #![feature(never_type)] //! //! 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}; //! //! /// `futures` version of `CountDown.wait` //! /// //! /// This returns a future that must be polled to completion //! fn wait<T>(mut timer: T) -> impl Future<Item = T, Error = !> //! where //! T: hal::timer::CountDown, //! { //! let mut timer = Some(timer); //! future::poll_fn(move || { //! try_nb!(timer.as_mut().unwrap().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().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().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 = ! //! loopback.poll().unwrap(); //! # break; //! } //! } //! //! # mod stm32f30x_hal { //! # pub struct Timer6; //! # impl ::hal::timer::CountDown for Timer6 { //! # type Time = (); //! # //! # fn start<T>(&mut self, _: T) where T: Into<()> {} //! # fn wait(&mut self) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) } //! # } //! # //! # pub struct Serial1; //! # impl ::hal::serial::Read<u8> for Serial1 { //! # type Error = !; //! # fn read(&mut self) -> ::nb::Result<u8, !> { Err(::nb::Error::WouldBlock) } //! # } //! # impl ::hal::serial::Write<u8> for Serial1 { //! # type Error = !; //! # fn flush(&mut self) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) } //! # fn write(&mut self, _: u8) -> ::nb::Result<(), !> { 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`. //! //! ``` //! #![feature(generator_trait)] //! #![feature(generators)] //! # #![feature(never_type)] //! //! extern crate embedded_hal as hal; //! //! #[macro_use(await)] //! extern crate nb; //! //! use std::ops::Generator; //! //! 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" //! await!(timer.wait()).unwrap(); // NOTE(unwrap) E = ! //! //! state = !state; //! //! if state { //! led.on(); //! } else { //! led.off(); //! } //! } //! }); //! //! let mut loopback = (move || { //! loop { //! let byte = await!(serial.read()).unwrap(); //! await!(serial.write(byte)).unwrap(); //! } //! }); //! //! // Event loop //! loop { //! blinky.resume(); //! loopback.resume(); //! # break; //! } //! } //! //! # mod stm32f30x_hal { //! # pub struct Serial1; //! # impl Serial1 { //! # pub fn read(&mut self) -> ::nb::Result<u8, !> { Err(::nb::Error::WouldBlock) } //! # pub fn write(&mut self, _: u8) -> ::nb::Result<(), !> { Err(::nb::Error::WouldBlock) } //! # } //! # pub struct Timer6; //! # impl Timer6 { //! # pub fn wait(&mut self) -> ::nb::Result<(), !> { 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.write(byte))?; //! } //! //! Ok(()) //! } //! //! # fn main() {} //! ``` //! //! - Blocking serial read with timeout //! //! ``` //! extern crate embedded_hal as hal; //! extern crate nb; //! //! use hal::prelude::*; //! //! enum Error<E> { //! /// Serial interface error //! Serial(E), //! TimedOut, //! } //! //! fn read_with_timeout<S, T>( //! serial: &mut S, //! timer: &mut T, //! timeout: T::Time, //! ) -> Result<u8, Error<S::Error>> //! where //! T: hal::timer::CountDown, //! S: hal::serial::Read<u8>, //! { //! timer.start(timeout); //! //! loop { //! match serial.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.wait() { //! Err(nb::Error::Other(e)) => { //! // The error type specified by `timer.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 //! //! ``` //! #![feature(conservative_impl_trait)] //! #![feature(generators)] //! #![feature(generator_trait)] //! //! extern crate embedded_hal as hal; //! #[macro_use(await)] //! extern crate nb; //! //! use std::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 { //! await!(spi.send(buffer[i]))?; //! buffer[i] = await!(spi.read())?; //! } //! //! Ok((spi, buffer)) //! } //! } //! //! # fn main() {} //! ``` //! //! - Buffered serial interface with periodic flushing in interrupt handler //! //! ``` //! # #![feature(never_type)] //! extern crate embedded_hal as hal; //! extern crate nb; //! //! use hal::prelude::*; //! //! fn flush<S>(serial: &mut S, cb: &mut CircularBuffer) //! where //! S: hal::serial::Write<u8, Error = !>, //! { //! loop { //! if let Some(byte) = cb.peek() { //! match serial.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> ::std::ops::Deref for RefMut<'a, T> { //! # type Target = T; //! # fn deref(&self) -> &T { self.0 } //! # } //! # impl<'a, T> ::std::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 = !; //! # fn write(&mut self, _: u8) -> nb::Result<(), !> { Err(::nb::Error::WouldBlock) } //! # fn flush(&mut self) -> nb::Result<(), !> { 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)] #![deny(warnings)] #![feature(never_type)] #![no_std] extern crate embedded_hal; extern crate nb; pub use embedded_hal::blocking; pub use embedded_hal::serial; pub use embedded_hal::spi; pub use embedded_hal::PwmPin; #[cfg(feature = "unproven")] pub use embedded_hal::{Capture, Direction, Pwm, Qei}; pub mod digital; pub mod prelude; pub mod timer;