pio: implement open-drain/multi-drive API

Author: sundbom-grepit

CHANGELOG.md

@@ -7,6 +7,7 @@
 - [Integration](https://crates.io/crates/mcan-core) with the
 [`mcan`](https://crates.io/crates/mcan) crate.
 - Implementation of blocking::i2c::Transactional trait from [embedded-hal](https://crates.io/crates/embedded-hal) for TWI device.
+- PIO: open-drain/multi-driver support
 
 ### Changed
 

hal/src/pio/dynpin.rs

@@ -73,6 +73,7 @@ pub enum DynPinMode {
     Reset,
     Peripheral(DynPeripheral),
     Output,
+    OpenDrain,
     Input,
 }
 

hal/src/pio/pin.rs

@@ -55,6 +55,10 @@ impl generics::Sealed for Input {}
 pub enum Output {}
 impl generics::Sealed for Output {}
 
+/// Type indicating that the [`Pin`] is an open drain
+pub enum OpenDrain {}
+impl generics::Sealed for OpenDrain {}
+
 //================================================================================
 // Peripheral configurations
 //================================================================================
@@ -117,6 +121,10 @@ impl PinMode for Output {
     const DYN: DynPinMode = DynPinMode::Output;
 }
 
+impl PinMode for OpenDrain {
+    const DYN: DynPinMode = DynPinMode::OpenDrain;
+}
+
 impl PinMode for Input {
     const DYN: DynPinMode = DynPinMode::Input;
 }
@@ -207,6 +215,15 @@ where
         pin
     }
 
+    /// Configures tis pin to operate as an [`OpenDrain`] [`Pin`].
+    #[inline]
+    pub fn into_opendrain(self, cfg: PullDir) -> Pin<I, OpenDrain> {
+        let mut pin: Pin<I, OpenDrain> = self.into_mode();
+        pin.set_pull_dir(cfg);
+
+        pin
+    }
+
     /// Configures this [`Pin`] to operate as an [`Input`] [`Pin`].
     #[inline]
     pub fn into_input(self, cfg: PullDir) -> Pin<I, Input> {
@@ -423,6 +440,25 @@ where
     }
 }
 
+impl<I> OutputPin for Pin<I, OpenDrain>
+where
+    I: PinId,
+{
+    type Error = Infallible;
+
+    #[inline]
+    fn set_high(&mut self) -> Result<(), Self::Error> {
+        self.set_pull_dir(PullDir::PullUp);
+        Ok(())
+    }
+
+    #[inline]
+    fn set_low(&mut self) -> Result<(), Self::Error> {
+        self.set_pull_dir(PullDir::Floating);
+        Ok(())
+    }
+}
+
 #[cfg(feature = "unproven")]
 impl<I> ToggleableOutputPin for Pin<I, Output>
 where

hal/src/pio/reg.rs

@@ -23,6 +23,7 @@ pub(in crate::pio) trait RegisterInterface {
             DynPinMode::Reset => unimplemented!(),
             DynPinMode::Peripheral(a) => self.as_peripheral(a),
             DynPinMode::Output => self.as_output(),
+            DynPinMode::OpenDrain => self.as_opendrain(),
             DynPinMode::Input => self.as_input(),
         }
     }
@@ -67,6 +68,18 @@ pub(in crate::pio) trait RegisterInterface {
         self.reg().oer.write(|w| unsafe { w.bits(self.mask()) });
     }
 
+    #[inline]
+    fn as_opendrain(&mut self) {
+        // take pin from peripheral
+        self.reg().per.write(|w| unsafe { w.bits(self.mask()) });
+
+        // Enable multidrive
+        self.reg().mder.write(|w| unsafe { w.bits(self.mask()) });
+
+        // disable pin output, driver should not be connected
+        self.reg().odr.write(|w| unsafe { w.bits(self.mask()) });
+    }
+
     #[inline]
     fn as_input(&mut self) {
         // take pin from peripheral