Add TryFrom<u8> implementation for Channel

Fixes #168

Author: golemparts

Diff for: CHANGELOG.md

@@ -1,9 +1,11 @@
 # Changelog
 
-## 0.21.0 (TBD)
+## 0.21.0 (December 10, 2024)
 
 * Add support for Raspberry Pi Compute Module 5 Lite.
 * Add support for Raspberry Pi 500.
+* **Pwm**: (Breaking change) Add `InvalidChannel` error.
+* **Pwm**: Add `TryFrom<u8>` implementation for `Channel`.
 
 ## 0.20.0 (November 30, 2024)
 

Diff for: src/pwm.rs

@@ -75,13 +75,22 @@ pub enum Error {
     /// doesn't provide any of the common user-accessible system files
     /// that are used to identify the model and SoC.
     UnknownModel,
+    /// Invalid channel.
+    ///
+    /// The selected PWM channel is not available on this device. You may
+    /// encounter this error if the Raspberry Pi model only has a limited
+    /// number of channels, the selected channel hasn't been properly
+    /// configured in `/boot/firmware/config.txt`, or the channel isn't
+    /// supported by RPPAL.
+    InvalidChannel,
 }
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Error::Io(ref err) => write!(f, "I/O error: {}", err),
             Error::UnknownModel => write!(f, "Unknown Raspberry Pi model"),
+            Error::InvalidChannel => write!(f, "Invalid PWM channel"),
         }
     }
 }
@@ -118,6 +127,18 @@ impl fmt::Display for Channel {
     }
 }
 
+impl TryFrom<u8> for Channel {
+    type Error = Error;
+
+    fn try_from(value: u8) -> result::Result<Self, Self::Error> {
+        match value {
+            0 => Ok(Channel::Pwm0),
+            1 => Ok(Channel::Pwm1),
+            _ => Err(Error::InvalidChannel),
+        }
+    }
+}
+
 /// Output polarities.
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
 pub enum Polarity {