implement core::error::Error

this API has been stabilised with Rust 1.81.0. accordingly the MSRV has
been raised.

in order to implement `cause` the underlying error from the HAL must
also implement `core::error::Error`. otherwise the trait bound will not
be satisfied. as the trait has only just been stabilisied it is not yet
implemented by any HAL (except for `embedded-hal-mock` since it's
`std`).

however, for GPIO operations most HALs will anyway just use
`core::convert::Infallible` which in turn already implements
`core::error::Error`, thus this should work out of the box.

Author: rursprung

.github/workflows/CI.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [1.63.0, stable]
+        rust: [1.81.0, stable]
         features: ['']
     runs-on: ubuntu-latest
     steps:

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 * Add a `current_standby()` method to check if the driver is currently in standby mode.
+* `MotorError` and `Tb6612fngError` now implement `core::error::Error` (newly stabilised in Rust 1.81)
 
 ### Changed
 
@@ -20,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * **Breaking**: Renamed error types to their struct names
 * **Breaking**: Renamed `DriveCommand::Backwards` to `DriveCommand::Backward` to match
   `DriveCommand::Forward`
+* The MSRV has been updated to 1.81.0 due to `core::error::Error` being implemented
 
 ### Removed
 

Cargo.toml

@@ -2,7 +2,7 @@
 name = "tb6612fng"
 version = "0.2.0"
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.81"
 
 description = "A `no_std` driver for the TB6612FNG motor driver."
 repository = "https://github.com/rust-embedded-community/tb6612fng-rs"

README.md

@@ -27,7 +27,7 @@ A simple example for the STM32F4 microcontrollers is [available](examples/stm32f
 For the changelog please see the dedicated [CHANGELOG.md](CHANGELOG.md).
 
 ## Minimum Supported Rust Version (MSRV)
-This crate is guaranteed to compile on stable Rust 1.63 and up. It *might*
+This crate is guaranteed to compile on stable Rust 1.81 and up. It *might*
 compile with older versions but that may change in any new patch release.
 
 ## License

src/lib.rs

@@ -17,6 +17,8 @@
 #![deny(unused)]
 #![no_std]
 
+use core::error::Error;
+use core::fmt::{Debug, Formatter};
 use embedded_hal::digital::{OutputPin, StatefulOutputPin};
 use embedded_hal::pwm::SetDutyCycle;
 
@@ -33,13 +35,62 @@ pub enum MotorError<IN1Error, IN2Error, PWMError> {
     PwmError(PWMError),
 }
 
+impl<IN1Error: Debug, IN2Error: Debug, PWMError: Debug> core::fmt::Display
+    for MotorError<IN1Error, IN2Error, PWMError>
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        use MotorError::*;
+        match self {
+            InvalidSpeed => write!(f, "an invalid speed has been specified"),
+            In1Error(_) => write!(f, "failed to set the output of the IN1 pin"),
+            In2Error(_) => write!(f, "failed to set the output of the IN2 pin"),
+            PwmError(_) => write!(f, "failed to set the output of the PWM pin"),
+        }
+    }
+}
+
+impl<
+        IN1Error: Debug + Error + 'static,
+        IN2Error: Debug + Error + 'static,
+        PWMError: Debug + Error + 'static,
+    > Error for MotorError<IN1Error, IN2Error, PWMError>
+{
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        use MotorError::*;
+        match self {
+            InvalidSpeed => None,
+            In1Error(e) => Some(e),
+            In2Error(e) => Some(e),
+            PwmError(e) => Some(e),
+        }
+    }
+}
+
 /// Defines errors which can happen when calling [`Tb6612fng::new()`].
 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
 pub enum Tb6612fngError<STBYError> {
     /// An error in setting the initial output of the standby pin
     Standby(STBYError),
 }
 
+impl<STBYError: Debug> core::fmt::Display for Tb6612fngError<STBYError> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        use Tb6612fngError::*;
+        match self {
+            Standby(_) => write!(f, "failed to set the output of the standby pin"),
+        }
+    }
+}
+
+impl<STBYError: Debug + Error + 'static> Error for Tb6612fngError<STBYError> {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        use Tb6612fngError::*;
+        match self {
+            Standby(e) => Some(e),
+        }
+    }
+}
+
 /// Defines the possible drive commands.
 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
 pub enum DriveCommand {
@@ -89,6 +140,8 @@ where
     ///
     /// # Usage example
     /// ```
+    ///
+    /// # fn main() -> Result<(), Box<dyn core::error::Error>> {
     /// # use embedded_hal_mock::eh1::digital::Mock as PinMock;
     /// # use embedded_hal_mock::eh1::pwm::Mock as PwmMock;
     /// # use embedded_hal_mock::eh1::pwm::Transaction as PwmTransaction;
@@ -113,10 +166,9 @@ where
     /// # let mut standby_ = standby.clone();
     ///
     /// use tb6612fng::{Motor, Tb6612fng};
-    ///
     /// let controller = Tb6612fng::new(
-    ///     Motor::new(motor_a_in1, motor_a_in2, motor_a_pwm).unwrap(),
-    ///     Motor::new(motor_b_in1, motor_b_in2, motor_b_pwm).unwrap(),
+    ///     Motor::new(motor_a_in1, motor_a_in2, motor_a_pwm)?,
+    ///     Motor::new(motor_b_in1, motor_b_in2, motor_b_pwm)?,
     ///     standby,
     /// );
     ///
@@ -127,6 +179,8 @@ where
     /// # motor_b_in2_.done();
     /// # motor_b_pwm_.done();
     /// # standby_.done();
+    /// # Ok(())
+    /// # }
     /// ```
     #[allow(clippy::type_complexity)]
     pub fn new(