feat: introduce a sensor abstraction

.github/workflows/build-deploy-docs.yml

@@ -48,7 +48,7 @@ jobs:
 
       - name: Build rustdoc docs
         run: |
-          cargo doc -p riot-rs --features bench,csprng,executor-thread,external-interrupts,hwrng,i2c,no-boards,random,threading,usb
+          cargo doc -p riot-rs --features bench,csprng,executor-thread,external-interrupts,hwrng,i2c,no-boards,random,sensors,threading,usb
           echo "<meta http-equiv=\"refresh\" content=\"0; url=riot_rs\">" > target/doc/index.html
           mkdir -p ./_site/dev/docs/api && mv target/doc/* ./_site/dev/docs/api
 

.github/workflows/main.yml

@@ -116,7 +116,7 @@ jobs:
       # TODO: we'll eventually want to enable relevant features
       - name: Run crate tests
         run: |
-            cargo test --no-default-features --features i2c,no-boards -p riot-rs -p riot-rs-embassy -p riot-rs-embassy-common -p riot-rs-runqueue -p riot-rs-threads -p riot-rs-macros
+            cargo test --no-default-features --features i2c,no-boards -p riot-rs -p riot-rs-embassy -p riot-rs-embassy-common -p riot-rs-runqueue -p riot-rs-sensors -p riot-rs-threads -p riot-rs-macros
             cargo test -p rbi -p ringbuffer -p coapcore
 
       # We need to set `RUSTDOCFLAGS` as well in the following jobs, because it
@@ -176,7 +176,7 @@ jobs:
       - name: clippy
         uses: clechasseur/rs-clippy-check@v3
         with:
-          args: --verbose --locked --features no-boards,external-interrupts -p riot-rs -p riot-rs-boards -p riot-rs-chips -p riot-rs-debug -p riot-rs-embassy -p riot-rs-embassy-common -p riot-rs-macros -p riot-rs-random -p riot-rs-rt -p riot-rs-threads -p riot-rs-utils -- --deny warnings
+          args: --verbose --locked --features no-boards,external-interrupts,sensors -p riot-rs -p riot-rs-boards -p riot-rs-chips -p riot-rs-debug -p riot-rs-embassy -p riot-rs-embassy-common -p riot-rs-macros -p riot-rs-random -p riot-rs-rt -p riot-rs-sensors -p riot-rs-threads -p riot-rs-utils -- --deny warnings
 
       - run: echo 'RUSTFLAGS=--cfg context="esp32c6"' >> $GITHUB_ENV
       - name: clippy for ESP32
@@ -206,7 +206,7 @@ jobs:
       - run: echo 'RUSTFLAGS=' >> $GITHUB_ENV
 
       - name: rustdoc
-        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features bench,csprng,executor-thread,external-interrupts,hwrng,i2c,no-boards,random,threading,usb
+        run: RUSTDOCFLAGS='-D warnings' cargo doc -p riot-rs --features bench,csprng,executor-thread,external-interrupts,hwrng,i2c,no-boards,random,sensors,threading,usb
 
       - name: rustdoc for ESP32
         run: RUSTDOCFLAGS='-D warnings --cfg context="esp32c6"' cargo doc --target=riscv32imac-unknown-none-elf --features external-interrupts,i2c,esp-hal/esp32c6,esp-hal-embassy/esp32c6 -p riot-rs-esp

Cargo.toml

@@ -18,6 +18,7 @@ members = [
   "src/riot-rs-nrf",
   "src/riot-rs-random",
   "src/riot-rs-rp",
+  "src/riot-rs-sensors",
   "src/riot-rs-stm32",
   "tests/benchmarks/bench_sched_flags",
   "tests/benchmarks/bench_sched_yield",
@@ -85,9 +86,11 @@ riot-rs-boards = { path = "src/riot-rs-boards", default-features = false }
 riot-rs-debug = { path = "src/riot-rs-debug", default-features = false }
 riot-rs-embassy = { path = "src/riot-rs-embassy", default-features = false }
 riot-rs-embassy-common = { path = "src/riot-rs-embassy-common" }
+riot-rs-macros = { path = "src/riot-rs-macros" }
 riot-rs-random = { path = "src/riot-rs-random" }
 riot-rs-rt = { path = "src/riot-rs-rt" }
 riot-rs-runqueue = { path = "src/riot-rs-runqueue" }
+riot-rs-sensors = { path = "src/riot-rs-sensors" }
 riot-rs-stm32 = { path = "src/riot-rs-stm32" }
 riot-rs-utils = { path = "src/riot-rs-utils", default-features = false }
 
@@ -102,6 +105,7 @@ once_cell = { version = "=1.19.0", default-features = false, features = [
   "critical-section",
 ] }
 paste = { version = "1.0" }
+pin-project = "1.1.6"
 static_cell = { version = "2.0.0", features = ["nightly"] }
 
 [profile.dev]

src/riot-rs-macros/Cargo.toml

@@ -32,3 +32,13 @@ trybuild = "1.0.89"
 
 [lib]
 proc-macro = true
+
+[features]
+# These features could be codegened
+max-reading-value-min-count-2 = []
+max-reading-value-min-count-3 = []
+max-reading-value-min-count-4 = []
+max-reading-value-min-count-6 = []
+max-reading-value-min-count-7 = []
+max-reading-value-min-count-9 = []
+max-reading-value-min-count-12 = []

src/riot-rs-macros/src/define_count_adjusted_sensor_enums.rs

@@ -0,0 +1,134 @@
+/// Generates sensor-related enums whose number of variants needs to be adjusted based on Cargo
+/// features, to accommodate the sensor driver returning the largest number of values.
+///
+/// One single type must be defined so that it can be used in the Future returned by sensor
+/// drivers, which must be the same for every sensor driver so it can be part of the `Sensor`
+/// trait.
+#[proc_macro]
+pub fn define_count_adjusted_sensor_enums(_item: TokenStream) -> TokenStream {
+    use quote::quote;
+
+    #[allow(clippy::wildcard_imports)]
+    use define_count_adjusted_enum::*;
+
+    // The order of these feature-gated statements is important as these features are not meant to
+    // be mutually exclusive.
+    #[allow(unused_variables, reason = "overridden by feature selection")]
+    let count = 1;
+    #[cfg(feature = "max-reading-value-min-count-2")]
+    let count = 2;
+    #[cfg(feature = "max-reading-value-min-count-3")]
+    let count = 3;
+    #[cfg(feature = "max-reading-value-min-count-4")]
+    let count = 4;
+    #[cfg(feature = "max-reading-value-min-count-6")]
+    let count = 6;
+    #[cfg(feature = "max-reading-value-min-count-7")]
+    let count = 7;
+    #[cfg(feature = "max-reading-value-min-count-9")]
+    let count = 9;
+    #[cfg(feature = "max-reading-value-min-count-12")]
+    let count = 12;
+
+    let physical_values_variants = (1..=count).map(|i| {
+        let variant = variant_name(i);
+        quote! { #variant([Value; #i]) }
+    });
+    let physical_values_first_value = (1..=count).map(|i| {
+        let variant = variant_name(i);
+        quote! {
+            Self::#variant(values) => {
+                if let Some(value) = values.first() {
+                    *value
+                } else {
+                    // NOTE(no-panic): there is always at least one value
+                    unreachable!();
+                }
+            }
+        }
+    });
+
+    let reading_axes_variants = (1..=count).map(|i| {
+        let variant = variant_name(i);
+        quote! { #variant([ReadingAxis; #i]) }
+    });
+
+    let values_iter = (1..=count)
+        .map(|i| {
+            let variant = variant_name(i);
+            quote! { Self::#variant(values) => values.iter().copied() }
+        })
+        .collect::<Vec<_>>();
+
+    let expanded = quote! {
+        /// Values returned by a sensor driver.
+        ///
+        /// This type implements [`Reading`] to iterate over the values.
+        ///
+        /// # Note
+        ///
+        /// This type is automatically generated, the number of variants is automatically adjusted.
+        #[derive(Debug, Copy, Clone)]
+        pub enum Values {
+            #[doc(hidden)]
+            #(#physical_values_variants),*
+        }
+
+        impl Reading for Values {
+            fn value(&self) -> Value {
+                match self {
+                    #(#physical_values_first_value),*
+                }
+            }
+
+            fn values(&self) -> impl ExactSizeIterator<Item = Value> {
+                match self {
+                    #(#values_iter),*
+                }
+            }
+        }
+
+        /// Metadata required to interpret values returned by [`Sensor::wait_for_reading()`].
+        ///
+        /// # Note
+        ///
+        /// This type is automatically generated, the number of variants is automatically adjusted.
+        #[derive(Debug, Copy, Clone)]
+        pub enum ReadingAxes {
+            #[doc(hidden)]
+            #(#reading_axes_variants),*,
+        }
+
+        impl ReadingAxes {
+            /// Returns an iterator over the underlying [`ReadingAxis`] items.
+            ///
+            /// For a given sensor driver, the number and order of items match the one of
+            /// [`Values`].
+            /// [`Iterator::zip()`] can be useful to zip the returned iterator with the one
+            /// obtained with [`Reading::values()`].
+            pub fn iter(&self) -> impl Iterator<Item = ReadingAxis> + '_ {
+                match self {
+                    #(#values_iter),*,
+                }
+            }
+
+            /// Returns the first [`ReadingAxis`].
+            pub fn first(&self) -> ReadingAxis {
+                if let Some(value) = self.iter().next() {
+                    value
+                } else {
+                    // NOTE(no-panic): there is always at least one value.
+                    unreachable!();
+                }
+            }
+        }
+    };
+
+    TokenStream::from(expanded)
+}
+
+mod define_count_adjusted_enum {
+    pub fn variant_name(index: usize) -> syn::Ident {
+        quote::format_ident!("V{index}")
+    }
+}

src/riot-rs-macros/src/lib.rs

@@ -5,6 +5,7 @@ mod utils;
 use proc_macro::TokenStream;
 
 include!("config.rs");
+include!("define_count_adjusted_sensor_enums.rs");
 include!("spawner.rs");
 include!("task.rs");
 include!("thread.rs");

src/riot-rs-rt/linkme.x

@@ -5,6 +5,8 @@ SECTIONS {
   linkm2_EMBASSY_TASKS : { *(linkm2_EMBASSY_TASKS) } > FLASH
   linkme_USB_BUILDER_HOOKS : { *(linkme_USB_BUILDER_HOOKS) } > FLASH
   linkm2_USB_BUILDER_HOOKS : { *(linkm2_USB_BUILDER_HOOKS) } > FLASH
+  linkme_SENSOR_REFS : { *(linkme_SENSOR_REFS) } > FLASH
+  linkm2_SENSOR_REFS : { *(linkm2_SENSOR_REFS) } > FLASH
   linkme_THREAD_FNS : { *(linkme_THREAD_FNS) } > FLASH
   linkm2_THREAD_FNS : { *(linkm2_THREAD_FNS) } > FLASH
 }

src/riot-rs-sensors/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "riot-rs-sensors"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+
+[lints]
+workspace = true
+
+[dependencies]
+defmt = { workspace = true, optional = true }
+embassy-sync = { workspace = true }
+linkme = { workspace = true }
+pin-project = { workspace = true }
+riot-rs-macros = { workspace = true }
+
+[features]
+defmt = ["dep:defmt"]
+
+# These features could be codegened
+max-reading-value-min-count-2 = ["riot-rs-macros/max-reading-value-min-count-2"]
+max-reading-value-min-count-3 = ["riot-rs-macros/max-reading-value-min-count-3"]
+max-reading-value-min-count-4 = ["riot-rs-macros/max-reading-value-min-count-4"]
+max-reading-value-min-count-6 = ["riot-rs-macros/max-reading-value-min-count-6"]
+max-reading-value-min-count-7 = ["riot-rs-macros/max-reading-value-min-count-7"]
+max-reading-value-min-count-9 = ["riot-rs-macros/max-reading-value-min-count-9"]
+max-reading-value-min-count-12 = [
+  "riot-rs-macros/max-reading-value-min-count-12",
+]

src/riot-rs-sensors/src/category.rs

@@ -0,0 +1,54 @@
+/// Categories a sensor driver can be part of.
+///
+/// A sensor driver can be part of multiple categories.
+///
+/// # For sensor driver implementors
+///
+/// Many mechanical sensor devices (e.g., accelerometers) include a temperature sensor as
+/// temperature may slightly affect the measurement results.
+/// If temperature readings are not exposed by the sensor driver, the sensor driver must not be
+/// considered part of a category that includes temperature ([`Category::Temperature`] or
+/// [`Category::AccelerometerTemperature`] in the case of an accelerometer).
+///
+/// Missing variants can be added when required.
+/// Please open an issue to discuss it.
+// Built upon https://doc.riot-os.org/group__drivers__saul.html#ga8f2dfec7e99562dbe5d785467bb71bbb
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum Category {
+    /// Accelerometer.
+    Accelerometer,
+    /// Accelerometer & temperature sensor.
+    AccelerometerTemperature,
+    /// Accelerometer & magnetometer & temperature sensor.
+    AccelerometerMagnetometerTemperature,
+    /// Ammeter (ampere meter).
+    Ammeter,
+    /// CO₂ gas sensor.
+    Co2Gas,
+    /// Color sensor.
+    Color,
+    /// Gyroscope.
+    Gyroscope,
+    /// Humidity sensor.
+    Humidity,
+    /// Humidity & temperature sensor.
+    HumidityTemperature,
+    /// Light sensor.
+    Light,
+    /// Magnetometer.
+    Magnetometer,
+    /// pH sensor.
+    Ph,
+    /// Pressure sensor.
+    Pressure,
+    /// Push button.
+    PushButton,
+    /// Temperature sensor.
+    Temperature,
+    /// TVOC sensor.
+    Tvoc,
+    /// Voltage sensor.
+    Voltage,
+}