Add gpio::last_write() for stateful output GPIOs

crates/api-desc/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Minor
 
+- Add `gpio::last_write()` function
 - Add `uart::{start,stop}()` and `uart::set_baudrate()` functions
 - Rename `clock` module to `timer`
 - Make all API functions return `isize`

crates/api-desc/src/gpio.rs

@@ -103,6 +103,16 @@ pub(crate) fn new() -> Item {
                 val: usize,
             } -> ()
         },
+        item! {
+            /// Returns the last logical value written to a GPIO.
+            ///
+            /// The initial output value counts as a write and would be returned if `write()` was
+            /// not called since last `configure()`.
+            fn last_write "gl" {
+                /// Index of the GPIO to query (must be configured as output).
+                gpio: usize,
+            } -> bool
+        },
     ];
     Item::Mod(Mod { docs, name, items })
 }

crates/board/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Major
 
+- Add `gpio::Api::last_write()` for stateful output GPIOs
 - Add `uart::Api` functions to start, stop, and set the baudrate
 - Remove `Unsupported` and `UnsupportedCrypto` implementations
 - Change `syscall` return type to `Option<Result<u31, Error>>`

crates/board/src/gpio.rs

@@ -53,4 +53,7 @@ pub trait Api: Support<usize> + Send {
 
     /// Writes to a GPIO (must be configured as output).
     fn write(gpio: Id<Self>, value: bool) -> Result<(), Error>;
+
+    /// Returns the last logical value written to a GPIO (must be configured as output).
+    fn last_write(gpio: Id<Self>) -> Result<bool, Error>;
 }

crates/prelude/CHANGELOG.md

@@ -13,6 +13,7 @@
 
 ### Minor
 
+- Add `gpio::Gpio::{last_write,toggle}()` for stateful output GPIOs
 - Add `uart::UartBuilder` and `uart::Uart::new()` to configure a UART
 - Add `serial::DelimitedReader` to read delimited frames from serial
 - Add `serial::Listener` to listen for serial events

crates/prelude/src/gpio.rs

@@ -91,6 +91,12 @@ pub fn write(gpio: usize, value: bool) {
     convert_unit(unsafe { api::write(params) }).unwrap();
 }
 
+/// Returns the last logical value written to a GPIO (must be configured as output).
+pub fn last_write(gpio: usize) -> bool {
+    let params = api::last_write::Params { gpio };
+    convert_bool(unsafe { api::last_write(params) }).unwrap()
+}
+
 /// GPIO that disconnects on drop.
 pub struct Gpio(usize);
 
@@ -116,4 +122,14 @@ impl Gpio {
     pub fn write(&self, value: bool) {
         write(self.0, value)
     }
+
+    /// Returns the last logical value written to a GPIO (must be configured as output).
+    pub fn last_write(&self) -> bool {
+        last_write(self.0)
+    }
+
+    /// Toggles the logical value of a GPIO (must be configured as output).
+    pub fn toggle(&self) {
+        self.write(!self.last_write());
+    }
 }

crates/runner-nordic/src/board/gpio.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use embedded_hal::digital::v2::{InputPin, OutputPin, PinState};
+use embedded_hal::digital::v2::{InputPin, OutputPin, PinState, StatefulOutputPin as _};
 use nrf52840_hal::gpio::{
     Disconnected, Floating, Input, Level, OpenDrain, OpenDrainConfig, OpenDrainIO, Output, Pin,
     PullDown, PullUp, PushPull,
@@ -83,6 +83,22 @@ impl Api for Impl {
             .map_err(|_| Error::world(0))
         })
     }
+
+    fn last_write(gpio: Id<Self>) -> Result<bool, Error> {
+        with_state(|state| {
+            match &mut state.gpios[*gpio].state {
+                State::Invalid => unreachable!(),
+                State::Disconnected(_)
+                | State::InputFloating(_)
+                | State::InputPullDown(_)
+                | State::InputPullUp(_) => return Err(Error::user(Code::InvalidState)),
+                State::OutputPushPull(x) => x.is_set_high(),
+                State::OutputOpenDrain(x) => x.is_set_high(),
+                State::OutputOpenDrainIO(x) => x.is_set_high(),
+            }
+            .map_err(|_| Error::world(0))
+        })
+    }
 }
 
 pub fn syscall(x: u32, y: u32, z: u32) -> Result<u32, Error> {

crates/scheduler/CHANGELOG.md

@@ -10,6 +10,7 @@
 
 ### Minor
 
+- Support `gpio::last_write()` function
 - Support `uart::{start,stop,set_baudrate}()` functions
 - Migrate `clock` module to `timer`
 - Remove unstable `software-crypto` feature

crates/scheduler/src/call/gpio.rs

@@ -29,6 +29,7 @@ pub fn process<B: Board>(call: Api<DispatchSchedulerCall<B>>) {
         Api::Configure(call) => or_trap!("board-api-gpio", configure(call)),
         Api::Read(call) => or_trap!("board-api-gpio", read(call)),
         Api::Write(call) => or_trap!("board-api-gpio", write(call)),
+        Api::LastWrite(call) => or_trap!("board-api-gpio", last_write(call)),
     }
 }
 
@@ -76,3 +77,13 @@ fn write<B: Board>(call: SchedulerCall<B, api::write::Sig>) {
     };
     call.reply(result);
 }
+
+#[cfg(feature = "board-api-gpio")]
+fn last_write<B: Board>(call: SchedulerCall<B, api::last_write::Sig>) {
+    let api::last_write::Params { gpio } = call.read();
+    let result = try {
+        let gpio = Id::new(*gpio as usize).ok_or(Trap)?;
+        board::Gpio::<B>::last_write(gpio)
+    };
+    call.reply(result);
+}

examples/assemblyscript/api.ts

@@ -629,6 +629,16 @@
     // Logical value (0 or 1).
     val: usize,
   ): i32
+
+  // Returns the last logical value written to a GPIO.
+  //
+  // The initial output value counts as a write and would be returned if `write()` was
+  // not called since last `configure()`.
+  @external("env", "gl")
+  export declare function gpio_last_write(
+    // Index of the GPIO to query (must be configured as output).
+    gpio: usize,
+  ): i32
 // END OF MODULE gpio
 
 // START OF MODULE led