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Move reading functions from OutputPin trait to StatefulOutputPin #72

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May 12, 2018
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89 changes: 83 additions & 6 deletions src/digital.rs
Original file line number Diff line number Diff line change
@@ -2,19 +2,96 @@
/// Single digital output pin
pub trait OutputPin {
/// Is the output pin high?
fn is_high(&self) -> bool;

/// Is the output pin low?
fn is_low(&self) -> bool;

/// Sets the pin low
fn set_low(&mut self);

/// Sets the pin high
fn set_high(&mut self);
}

/// Output pin that can read its output state
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As I've mentioned before there's a distinction between a logical state and an electrical state. It should be made clear that this is meant to represent the logical (or register) state of a pin and not the electrical state.

#[cfg(feature = "unproven")]
pub trait StatefulOutputPin {
/// Is the pin set to high?
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A pin could also be logically floating so either it needs to be made clear that a tri-stated pin may not implement this trait or that the implicit assumption p.is_set_high() == !p.is_set_low() does not necessarily hold and should not be assumed.

fn is_set_high(&self) -> bool;

/// Is the pin set to low?
fn is_set_low(&self) -> bool;
}

/// Output pin that can be toggled
///
/// 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.
#[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.
///
/// ```
/// 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());
/// ```
#[cfg(feature = "unproven")]
pub mod toggleable {
use super::{OutputPin, StatefulOutputPin, ToggleableOutputPin};

/// Software-driven `toggle()` implementation.
pub trait Default: OutputPin + StatefulOutputPin {}

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
#[cfg(feature = "unproven")]
pub trait InputPin {