re-introduce usage of defmt

i had forgotten to completely remove the dependency in the now reverted
commit, thus the optional dependency still created a feature which
consuming crates could enable. removing it would be a breaking change.
this leaves two options:
* remove the `defmt` _dependency_ and add a dummy _feature_ of the same
  name, issuing a compile warning if it is enabled, eventually removing
  it in v2.0 if or when that will ever be released
* accept the fact that we already have the optional dependency and thus
  the feature and make use of it

this contains a few changes to the reverted commit:
* the feature is now called `defmt` rather than `defmt-03` (as that's
  the name of the implicit feature for the optional dependency)
* the `debug` output in `drive` is kept but downgraded to `trace` and
  slightly reworded (the speed is already present in the command)
* the `cfg`-guarded `use` is removed to make the code cleaner

This reverts commit d9da807.
(with minor adaptations)

Author: rursprung

.github/workflows/CI.yml

@@ -14,7 +14,7 @@ jobs:
       fail-fast: false
       matrix:
         rust: [1.81.0, stable]
-        features: ['']
+        features: ['', '--all-features']
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- next-header -->
 ## [Unreleased] - ReleaseDate
+
+### Added
+
+* Re-introduced usage of `defmt` (the dependency was still present, only its usage and the `defmt-03` feature were
+ removed before the previous release)
+
 ### Changed
 
 * Updated to `defmt` 1.0 (non-breaking change, backwards compatible with 0.3 through semver trick)

Cargo.toml

@@ -12,6 +12,7 @@ license = "MIT OR Apache-2.0"
 authors = ["Ralph Ursprung <[email protected]>", "ripytide <[email protected]>"]
 
 [features]
+defmt = ["dep:defmt", "embedded-hal/defmt-03"]
 
 [dependencies]
 embedded-hal = "1.0"

README.md

@@ -20,6 +20,9 @@ See the documentation for usage examples.
 * You plan on using a single motor with the standby feature: use `Motor` and control the standby pin manually
 * You plan on using a single motor without the standby feature: use `Motor`
 
+## Optional features
+* `defmt`: you can enable this feature to get a `defmt::Format` implementation for all structs & enums in this crate and a `defmt::trace` call for every speed change.
+
 ## Examples
 A simple example for the STM32F4 microcontrollers is [available](examples/stm32f4-single-motor-example/README.md).
 

src/lib.rs

@@ -9,6 +9,9 @@
 //! * You plan on using both motors without the standby feature: use two separate [`Motor`]s
 //! * You plan on using a single motor with the standby feature: use [`Motor`] and control the standby pin manually
 //! * You plan on using a single motor without the standby feature: use [`Motor`]
+//!
+//! ## Optional features
+//! * `defmt`: you can enable this feature to get a `defmt::Format` implementation for all structs & enums in this crate and a `defmt::trace` call for every speed change.
 
 #![forbid(unsafe_code)]
 #![deny(warnings)]
@@ -24,6 +27,7 @@ use embedded_hal::pwm::SetDutyCycle;
 
 /// Defines errors which can happen when calling [`Motor::drive()`].
 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum MotorError<IN1Error, IN2Error, PWMError> {
     /// An invalid speed has been defined. The speed must be given as a percentage value between 0 and 100 to be valid.
     InvalidSpeed,
@@ -68,6 +72,7 @@ impl<
 
 /// Defines errors which can happen when calling [`Tb6612fng::new()`].
 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum Tb6612fngError<STBYError> {
     /// An error in setting the initial output of the standby pin
     Standby(STBYError),
@@ -93,6 +98,7 @@ impl<STBYError: Debug + Error + 'static> Error for Tb6612fngError<STBYError> {
 
 /// Defines the possible drive commands.
 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum DriveCommand {
     /// Drive forward with the defined speed (in percentage)
     Forward(u8),
@@ -109,6 +115,7 @@ pub enum DriveCommand {
 /// Use the [`Motor`] struct directly if you only have one motor.
 /// See the crate-level comment for further details on when to use what.
 #[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct Tb6612fng<MAIN1, MAIN2, MAPWM, MBIN1, MBIN2, MBPWM, STBY> {
     /// The first motor, labelled as 'A' on the chip
     pub motor_a: Motor<MAIN1, MAIN2, MAPWM>,
@@ -245,6 +252,7 @@ where
 /// This is unaware of the standby pin. If you plan on using both motors and the standby feature then use the [`Tb6612fng`] struct instead.
 /// See the crate-level comment for further details on when to use what.
 #[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct Motor<IN1, IN2, PWM> {
     in1: IN1,
     in2: IN2,
@@ -350,6 +358,9 @@ where
             }
         }
 
+        #[cfg(feature = "defmt")]
+        defmt::trace!("driving: {}", drive_command);
+
         self.pwm
             .set_duty_cycle_percent(speed)
             .map_err(MotorError::PwmError)?;