Merge #108

108: Add fallible version of the digital traits and deprecate the current ones r=ryankurte a=eldruin

There seems to be an agreement in [#100](#100 (comment)) on how to proceed with the fallible traits.
This adds the fallible traits under `digital::v2` and marks the current ones as deprecated.

Co-authored-by: Diego Barrios Romero <eldruin@gmail.com>
Co-authored-by: Ryan <ryankurte@users.noreply.github.com>

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+- A new version of the digital `OutputPin`, `StatefulOutputPin`, `ToggleableOutputPin`
+  and `InputPin` traits has been added under `digital::v2`. These traits are now
+  fallible and their methods now return a `Result` type as setting an output pin
+  and reading an input pin could potentially fail.
+  See [here](https://github.com/rust-embedded/embedded-hal/issues/95) for more info.
+
+### Changed
+- The current versions of the `OutputPin`, `StatefulOutputPin`, `ToggleableOutputPin`
+  and `InputPin` traits have been marked as deprecated. Please use the new versions
+  included in `digital::v2`.
+  See [here](https://github.com/rust-embedded/embedded-hal/issues/95) for more info.
+
+
 ## [v0.2.2] - 2018-11-03
 
 ### Added
@@ -21,6 +35,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - Updated docs to clarify I2C address bit widths and expectations.
 
+
 ## [v0.2.1] - 2018-05-14
 
 ### Changed

src/digital/mod.rs

@@ -0,0 +1,155 @@
+//! Digital I/O
+//!
+//! The traits in this module are now deprecated. Please use the new versions included
+//! in `digital::v2`.
+
+/// Single digital push-pull output pin
+///
+/// *This version of the trait is now deprecated. Please use the new `OutputPin` trait in
+/// `digital::v2::OutputPin`*.
+#[deprecated(since = "0.2.2", note = "Deprecated because the methods cannot return errors. \
+                                      Users should use the traits in digital::v2.")]
+pub trait OutputPin {
+    /// Drives the pin low
+    ///
+    /// *NOTE* the actual electrical state of the pin may not actually be low, e.g. due to external
+    /// electrical sources
+    fn set_low(&mut self);
+
+    /// Drives the pin high
+    ///
+    /// *NOTE* the actual electrical state of the pin may not actually be high, e.g. due to external
+    /// electrical sources
+    fn set_high(&mut self);
+}
+
+/// Push-pull output pin that can read its output state
+///
+/// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
+///
+/// *This version of the trait is now deprecated. Please use the new `StatefulOutputPin` trait in
+/// `digital::v2::StatefulOutputPin`*.
+#[deprecated(since = "0.2.2", note = "Deprecated because the methods cannot return errors. \
+                                      Users should use the traits in digital::v2.")]
+#[cfg(feature = "unproven")]
+pub trait StatefulOutputPin {
+    /// Is the pin in drive high mode?
+    ///
+    /// *NOTE* this does *not* read the electrical state of the pin
+    fn is_set_high(&self) -> bool;
+
+    /// Is the pin in drive low mode?
+    ///
+    /// *NOTE* this does *not* read the electrical state of the pin
+    fn is_set_low(&self) -> bool;
+}
+
+/// Output pin that can be toggled
+///
+/// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
+///
+/// *This version of the trait is now deprecated. Please use the new `ToggleableOutputPin`
+/// trait in `digital::v2::ToggleableOutputPin`*.
+///
+/// See [toggleable](toggleable) to use a software implementation if
+/// both [OutputPin](trait.OutputPin.html) and
+/// [StatefulOutputPin](trait.StatefulOutputPin.html) are
+/// implemented. Otherwise, implement this using hardware mechanisms.
+#[deprecated(since = "0.2.2", note = "Deprecated because the methods cannot return errors. \
+                                      Users should use the traits in digital::v2.")]
+#[cfg(feature = "unproven")]
+pub trait ToggleableOutputPin {
+    /// Toggle pin output.
+    fn toggle(&mut self);
+}
+
+/// If you can read **and** write the output state, a pin is
+/// toggleable by software.
+///
+/// *This version of the module is now deprecated. Please use the new `toggleable` module in
+/// `digital::v2::toggleable`*.
+///
+/// ```
+/// use embedded_hal::digital::{OutputPin, StatefulOutputPin, ToggleableOutputPin};
+/// use embedded_hal::digital::toggleable;
+///
+/// /// A virtual output pin that exists purely in software
+/// struct MyPin {
+///     state: bool
+/// }
+///
+/// impl OutputPin for MyPin {
+///    fn set_low(&mut self) {
+///        self.state = false;
+///    }
+///    fn set_high(&mut self) {
+///        self.state = true;
+///    }
+/// }
+///
+/// impl StatefulOutputPin for MyPin {
+///    fn is_set_low(&self) -> bool {
+///        !self.state
+///    }
+///    fn is_set_high(&self) -> bool {
+///        self.state
+///    }
+/// }
+///
+/// /// Opt-in to the software implementation.
+/// impl toggleable::Default for MyPin {}
+///
+/// let mut pin = MyPin { state: false };
+/// pin.toggle();
+/// assert!(pin.is_set_high());
+/// pin.toggle();
+/// assert!(pin.is_set_low());
+/// ```
+#[deprecated(since = "0.2.2", note = "Deprecated because the methods cannot return errors. \
+                                      Users should use the traits in digital::v2.")]
+#[cfg(feature = "unproven")]
+pub mod toggleable {
+    #[allow(deprecated)]
+    use super::{OutputPin, StatefulOutputPin, ToggleableOutputPin};
+
+    /// Software-driven `toggle()` implementation.
+    ///
+    /// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
+    #[allow(deprecated)]
+    pub trait Default: OutputPin + StatefulOutputPin {}
+
+    #[allow(deprecated)]
+    impl<P> ToggleableOutputPin for P
+    where
+        P: Default,
+    {
+        /// Toggle pin output
+        fn toggle(&mut self) {
+            if self.is_set_low() {
+                self.set_high();
+            } else {
+                self.set_low();
+            }
+        }
+    }
+}
+
+/// Single digital input pin
+///
+/// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
+///
+/// *This version of the trait is now deprecated. Please use the new `InputPin` trait in
+/// `digital::v2::InputPin`*.
+#[deprecated(since = "0.2.2", note = "Deprecated because the methods cannot return errors. \
+                                      Users should use the traits in digital::v2.")]
+#[cfg(feature = "unproven")]
+pub trait InputPin {
+    /// Is the input pin high?
+    fn is_high(&self) -> bool;
+
+    /// Is the input pin low?
+    fn is_low(&self) -> bool;
+}
+
+/// Improved version of the digital traits where the methods can also return an error.
+pub mod v2;

src/digital.rs → src/digital/v2.rs

@@ -1,34 +1,37 @@
-//! Digital I/O
+/// Digital I/O
 
 /// Single digital push-pull output pin
 pub trait OutputPin {
+    /// Error type
+    type Error;
+
     /// Drives the pin low
     ///
     /// *NOTE* the actual electrical state of the pin may not actually be low, e.g. due to external
     /// electrical sources
-    fn set_low(&mut self);
+    fn set_low(&mut self) -> Result<(), Self::Error>;
 
     /// Drives the pin high
     ///
     /// *NOTE* the actual electrical state of the pin may not actually be high, e.g. due to external
     /// electrical sources
-    fn set_high(&mut self);
+    fn set_high(&mut self) -> Result<(), Self::Error>;
 }
 
 /// Push-pull output pin that can read its output state
 ///
 /// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
 #[cfg(feature = "unproven")]
-pub trait StatefulOutputPin {
+pub trait StatefulOutputPin : OutputPin {
     /// Is the pin in drive high mode?
     ///
     /// *NOTE* this does *not* read the electrical state of the pin
-    fn is_set_high(&self) -> bool;
+    fn is_set_high(&self) -> Result<bool, Self::Error>;
 
     /// Is the pin in drive low mode?
     ///
     /// *NOTE* this does *not* read the electrical state of the pin
-    fn is_set_low(&self) -> bool;
+    fn is_set_low(&self) -> Result<bool, Self::Error>;
 }
 
 /// Output pin that can be toggled
@@ -41,48 +44,55 @@ pub trait StatefulOutputPin {
 /// implemented. Otherwise, implement this using hardware mechanisms.
 #[cfg(feature = "unproven")]
 pub trait ToggleableOutputPin {
+    /// Error type
+    type Error;
+
     /// Toggle pin output.
-    fn toggle(&mut self);
+    fn toggle(&mut self) -> Result<(), Self::Error>;
 }
 
 /// If you can read **and** write the output state, a pin is
 /// toggleable by software.
 ///
 /// ```
-/// use embedded_hal::digital::{OutputPin, StatefulOutputPin, ToggleableOutputPin};
-/// use embedded_hal::digital::toggleable;
+/// use embedded_hal::digital::v2::{OutputPin, StatefulOutputPin, ToggleableOutputPin};
+/// use embedded_hal::digital::v2::toggleable;
 ///
 /// /// A virtual output pin that exists purely in software
 /// struct MyPin {
 ///     state: bool
 /// }
 ///
 /// impl OutputPin for MyPin {
-///    fn set_low(&mut self) {
+///    type Error = void::Void;
+///
+///    fn set_low(&mut self) -> Result<(), Self::Error> {
 ///        self.state = false;
+///        Ok(())
 ///    }
-///    fn set_high(&mut self) {
+///    fn set_high(&mut self) -> Result<(), Self::Error> {
 ///        self.state = true;
+///        Ok(())
 ///    }
 /// }
 ///
 /// impl StatefulOutputPin for MyPin {
-///    fn is_set_low(&self) -> bool {
-///        !self.state
+///    fn is_set_low(&self) -> Result<bool, Self::Error> {
+///        Ok(!self.state)
 ///    }
-///    fn is_set_high(&self) -> bool {
-///        self.state
+///    fn is_set_high(&self) -> Result<bool, Self::Error> {
+///        Ok(self.state)
 ///    }
 /// }
 ///
 /// /// Opt-in to the software implementation.
 /// impl toggleable::Default for MyPin {}
 ///
 /// let mut pin = MyPin { state: false };
-/// pin.toggle();
-/// assert!(pin.is_set_high());
-/// pin.toggle();
-/// assert!(pin.is_set_low());
+/// pin.toggle().unwrap();
+/// assert!(pin.is_set_high().unwrap());
+/// pin.toggle().unwrap();
+/// assert!(pin.is_set_low().unwrap());
 /// ```
 #[cfg(feature = "unproven")]
 pub mod toggleable {
@@ -97,12 +107,14 @@ pub mod toggleable {
     where
         P: Default,
     {
+        type Error = P::Error;
+
         /// Toggle pin output
-        fn toggle(&mut self) {
-            if self.is_set_low() {
-                self.set_high();
+        fn toggle(&mut self) -> Result<(), Self::Error> {
+            if self.is_set_low()? {
+                self.set_high()
             } else {
-                self.set_low();
+                self.set_low()
             }
         }
     }
@@ -113,9 +125,12 @@ pub mod toggleable {
 /// *This trait is available if embedded-hal is built with the `"unproven"` feature.*
 #[cfg(feature = "unproven")]
 pub trait InputPin {
+    /// Error type
+    type Error;
+
     /// Is the input pin high?
-    fn is_high(&self) -> bool;
+    fn is_high(&self) -> Result<bool, Self::Error>;
 
     /// Is the input pin low?
-    fn is_low(&self) -> bool;
+    fn is_low(&self) -> Result<bool, Self::Error>;
 }

src/prelude.rs

@@ -15,10 +15,13 @@ pub use blocking::serial::Write as _embedded_hal_blocking_serial_Write;
 pub use blocking::spi::{
     Transfer as _embedded_hal_blocking_spi_Transfer, Write as _embedded_hal_blocking_spi_Write,
 };
+#[allow(deprecated)]
 #[cfg(feature = "unproven")]
 pub use digital::InputPin as _embedded_hal_digital_InputPin;
+#[allow(deprecated)]
 pub use digital::OutputPin as _embedded_hal_digital_OutputPin;
 #[cfg(feature = "unproven")]
+#[allow(deprecated)]
 pub use digital::ToggleableOutputPin as _embedded_hal_digital_ToggleableOutputPin;
 pub use serial::Read as _embedded_hal_serial_Read;
 pub use serial::Write as _embedded_hal_serial_Write;