Added RefCell blanket implementation for I2C to allow sharing, see rust-embedded#35

Signed-off-by: Daniel Egger <[email protected]>

Author: therealprof

src/blocking/i2c.rs

@@ -1,5 +1,7 @@
 //! Blocking I2C API
 
+use core::cell::RefCell;
+
 /// Blocking read
 pub trait Read {
     /// Error type
@@ -84,3 +86,93 @@ pub trait WriteRead {
         buffer: &mut [u8],
     ) -> Result<(), Self::Error>;
 }
+
+/// Blanket implementations to enable I2C bus sharing via RefCell
+
+/// # Example usage
+///
+/// ``` ignore
+/// let mut i2c = hal::I2c::i2c (...);
+///
+/// // Stash i2c instance into a RefCell for sharing
+/// let shared_i2c = RefCell::new(i2c);
+///
+/// // Pass it on to one or more drivers for devices on the same bus
+/// let mut driver_a = DriverA::new(&mut &shared_i2c);
+///
+/// // Use the shared bus with the drivers
+/// driver_a.do_stuff();
+///
+/// // Use it independently of a driver for direct bus interaction
+/// let mut data = [0; 2];
+/// shared_i2c.borrow_mut().read(0x11, &mut data);
+/// ```
+impl<'a, I> ::blocking::i2c::Read for &'a RefCell<I>
+where
+    I: ::blocking::i2c::Read,
+{
+    type Error = <I as Read>::Error;
+    fn read(&mut self, address: u8, buffer: &mut [u8]) -> Result<(), Self::Error> {
+        self.borrow_mut().read(address, buffer)
+    }
+}
+
+/// # Example usage
+///
+/// ``` ignore
+/// let mut i2c = hal::I2c::i2c (...);
+///
+/// // Stash i2c instance into a RefCell for sharing
+/// let shared_i2c = RefCell::new(i2c);
+///
+/// // Pass it on to one or more drivers for devices on the same bus
+/// let mut driver_a = DriverA::new(&mut &shared_i2c);
+///
+/// // Use the shared bus with the drivers
+/// driver_a.do_stuff();
+///
+/// // Use it independently of a driver for direct bus interaction
+/// shared_i2c.borrow_mut().write(0x33, &[0x01, 0x02]);
+/// ```
+impl<'a, I> ::blocking::i2c::Write for &'a RefCell<I>
+where
+    I: ::blocking::i2c::Write,
+{
+    type Error = <I as Write>::Error;
+    fn write(&mut self, addr: u8, bytes: &[u8]) -> Result<(), Self::Error> {
+        self.borrow_mut().write(addr, bytes)
+    }
+}
+
+/// # Example usage
+///
+/// ``` ignore
+/// let mut i2c = hal::I2c::i2c (...);
+///
+/// // Stash i2c instance into a RefCell for sharing
+/// let shared_i2c = RefCell::new(i2c);
+///
+/// // Pass it on to one or more drivers for devices on the same bus
+/// let mut driver_a = DriverA::new(&mut &shared_i2c);
+///
+/// // Use the shared bus with the drivers
+/// driver_a.do_stuff();
+///
+/// // Use it independently of a driver for direct bus interaction
+/// let mut data = [0; 2];
+/// shared_i2c.borrow_mut().write_read(0x22, &[0x00], &mut data);
+/// ```
+impl<'a, I> ::blocking::i2c::WriteRead for &'a RefCell<I>
+where
+    I: ::blocking::i2c::WriteRead,
+{
+    type Error = <I as WriteRead>::Error;
+    fn write_read(
+        &mut self,
+        address: u8,
+        bytes: &[u8],
+        buffer: &mut [u8],
+    ) -> Result<(), Self::Error> {
+        self.borrow_mut().write_read(address, bytes, buffer)
+    }
+}