Merge #298

298: Turn traits and execution model modules inside out r=therealprof a=eldruin

A proposal for discussion.
## Advantadges
- Place for execution-model-independent type definitions
    - For example useful for SPI modes 
- Fits better with users who might think of peripheral first, then execution model. - `@Sh3Rm4n` 
- Helps discoverability, since the modules are not "hidden" behind their execution model. - `@Rahix`
## Disadvantadges
- Breaks every last `embedded-hal`-dependent code
- Users may want to import several `embedded_hal::xxx::blocking` modules, for example, although there is no much reason to do so.
- There might be confusion between `embedded_hal::xxx::nb` and `embedded_hal::nb`.
## Open questions
- Reexport execution-model-independent types in `blocking`/`nb` submodules?
## Alternatives
Keep the structure as-is

Co-authored-by: Diego Barrios Romero <[email protected]>

Author: bors[bot]

CHANGELOG.md

@@ -15,9 +15,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - Swap PWM channel arguments to references
 - All trait methods have been renamed to remove the `try_` prefix (i.e. `try_send` -> `send`) for consistency.
-- Moved all traits into two modules depending on the execution model: `blocking` and `nb` (non-blocking).
+- Moved all traits into two sub modules for each feature depending on the execution model: `blocking` and `nb` (non-blocking). For example, the spi traits can now be found under `embedded_hal::spi::blocking` or `embedded_hal::spi::nb`.
+- Execution-model-independent definitions have been moved into the feature module. For example, SPI `Phase` is now defined in `embedded_hal::spi::Phase`. For convenience, these definitions are reexported in both of its blocking and non-blocking submodules.
 - Re-export `nb::{block!, Error, Result}` to avoid version mismatches. These should be used instead of
-  importing the `nb` crate directly in dependendent crates.
+  importing the `nb` crate directly in dependent crates.
 - `blocking::Serial`: renamed `bwrite_all` to `write`, `bflush` to `flush.
 - Removed `prelude` to avoid method name conflicts between different flavors (blocking, nb) of the same trait. Traits must now be manually imported.
 - Removed the various `Default` marker traits.

src/adc.rs

@@ -0,0 +1,95 @@
+//! Analog-digital conversion traits
+
+/// Non-blocking ADC traits
+pub mod nb {
+    /// A marker trait to identify MCU pins that can be used as inputs to an ADC channel.
+    ///
+    /// This marker trait denotes an object, i.e. a GPIO pin, that is ready for use as an input to the
+    /// ADC. As ADCs channels can be supplied by multiple pins, this trait defines the relationship
+    /// between the physical interface and the ADC sampling buffer.
+    ///
+    /// ```
+    /// # use core::marker::PhantomData;
+    /// # use embedded_hal::adc::nb::Channel;
+    ///
+    /// struct Adc1; // Example ADC with single bank of 8 channels
+    /// struct Gpio1Pin1<MODE>(PhantomData<MODE>);
+    /// struct Analog(()); // marker type to denote a pin in "analog" mode
+    ///
+    /// // GPIO 1 pin 1 can supply an ADC channel when it is configured in Analog mode
+    /// impl Channel<Adc1> for Gpio1Pin1<Analog> {
+    ///     type ID = u8; // ADC channels are identified numerically
+    ///
+    ///     fn channel(&self) -> Self::ID {
+    ///         7_u8 // GPIO pin 1 is connected to ADC channel 7
+    ///     }
+    /// }
+    ///
+    /// struct Adc2; // ADC with two banks of 16 channels
+    /// struct Gpio2PinA<MODE>(PhantomData<MODE>);
+    /// struct AltFun(()); // marker type to denote some alternate function mode for the pin
+    ///
+    /// // GPIO 2 pin A can supply an ADC channel when it's configured in some alternate function mode
+    /// impl Channel<Adc2> for Gpio2PinA<AltFun> {
+    ///     type ID = (u8, u8); // ADC channels are identified by bank number and channel number
+    ///
+    ///     fn channel(&self) -> Self::ID {
+    ///         (0, 3) // bank 0 channel 3
+    ///     }
+    /// }
+    /// ```
+    pub trait Channel<ADC> {
+        /// Channel ID type
+        ///
+        /// A type used to identify this ADC channel. For example, if the ADC has eight channels, this
+        /// might be a `u8`. If the ADC has multiple banks of channels, it could be a tuple, like
+        /// `(u8: bank_id, u8: channel_id)`.
+        type ID: Copy;
+
+        /// Get the specific ID that identifies this channel, for example `0_u8` for the first ADC
+        /// channel, if Self::ID is u8.
+        fn channel(&self) -> Self::ID;
+    }
+
+    /// ADCs that sample on single channels per request, and do so at the time of the request.
+    ///
+    /// This trait is the interface to an ADC that is configured to read a specific channel at the time
+    /// of the request (in contrast to continuous asynchronous sampling).
+    ///
+    /// ```
+    /// use embedded_hal::adc::nb::{Channel, OneShot};
+    ///
+    /// struct MyAdc; // 10-bit ADC, with 5 channels
+    /// # impl MyAdc {
+    /// #     pub fn power_up(&mut self) {}
+    /// #     pub fn power_down(&mut self) {}
+    /// #     pub fn do_conversion(&mut self, chan: u8) -> u16 { 0xAA55_u16 }
+    /// # }
+    ///
+    /// impl<WORD, PIN> OneShot<MyAdc, WORD, PIN> for MyAdc
+    /// where
+    ///    WORD: From<u16>,
+    ///    PIN: Channel<MyAdc, ID=u8>,
+    /// {
+    ///    type Error = ();
+    ///
+    ///    fn read(&mut self, pin: &mut PIN) -> nb::Result<WORD, Self::Error> {
+    ///        let chan = 1 << pin.channel();
+    ///        self.power_up();
+    ///        let result = self.do_conversion(chan);
+    ///        self.power_down();
+    ///        Ok(result.into())
+    ///    }
+    /// }
+    /// ```
+    pub trait OneShot<ADC, Word, Pin: Channel<ADC>> {
+        /// Error type returned by ADC methods
+        type Error;
+
+        /// Request that the ADC begin a conversion on the specified pin
+        ///
+        /// This method takes a `Pin` reference, as it is expected that the ADC will be able to sample
+        /// whatever channel underlies the pin.
+        fn read(&mut self, pin: &mut Pin) -> nb::Result<Word, Self::Error>;
+    }
+}