Auto merge of rust-embedded#3 - wose:feature/i2c, r=japaric

embedded-hal i2c traits implementation using i2cdev

I tested this on a Raspberry Pi 2 with an SDD1306 OLED display and a Si7021 humidity/temperature sensor (driver crates will follow soon).

However, I'm not quite sure about the address parameter. The i2cdev crate will use the address when creating the LinuxI2CDevice, the embedded-hal traits expect the device address as parameter. I just ignore this parameter in this implementation. Is this the right way to do it?

Author: homunkulus

Cargo.toml

@@ -10,6 +10,7 @@ version = "0.1.0"
 
 [dependencies]
 embedded-hal = "0.1.0"
+i2cdev = "0.3.1"
 spidev = "0.3.0"
 sysfs_gpio = "0.5.1"
 

src/lib.rs

@@ -15,15 +15,17 @@
 
 extern crate cast;
 extern crate embedded_hal as hal;
+pub extern crate i2cdev;
 pub extern crate spidev;
 pub extern crate sysfs_gpio;
 
 use std::io::{self, Write};
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::time::Duration;
 use std::{ops, thread};
 
 use cast::{u32, u64};
+use i2cdev::core::I2CDevice;
 use spidev::SpidevTransfer;
 
 /// Empty struct that provides delay functionality on top of `thread::sleep`
@@ -139,6 +141,87 @@ impl ops::DerefMut for Pin {
     }
 }
 
+/// Newtype around [`i2cdev::linux::LinuxI2CDevice`] that implements the `embedded-hal` traits
+///
+/// [`i2cdev::linux::LinuxI2CDevice`]: https://docs.rs/i2cdev/0.3.1/i2cdev/linux/struct.LinuxI2CDevice.html
+pub struct I2cdev {
+    inner: i2cdev::linux::LinuxI2CDevice,
+    path: PathBuf,
+    address: Option<u8>,
+}
+
+impl I2cdev {
+    /// See [`i2cdev::linux::LinuxI2CDevice::new`][0] for details.
+    ///
+    /// [0]: https://docs.rs/i2cdev/0.3.1/i2cdev/linux/struct.LinuxI2CDevice.html#method.new
+    pub fn new<P>(path: P) -> Result<Self, i2cdev::linux::LinuxI2CError>
+    where
+        P: AsRef<Path>,
+    {
+        let dev = I2cdev {
+            path: path.as_ref().to_path_buf(),
+            inner: i2cdev::linux::LinuxI2CDevice::new(path, 0)?,
+            address: None,
+        };
+        Ok(dev)
+    }
+
+    fn set_address(&mut self, address: u8) -> Result<(), i2cdev::linux::LinuxI2CError> {
+        if self.address != Some(address) {
+            self.inner = i2cdev::linux::LinuxI2CDevice::new(&self.path, address as u16)?;
+            self.address = Some(address);
+        }
+        Ok(())
+    }
+}
+
+impl hal::blocking::i2c::Read for I2cdev {
+    type Error = i2cdev::linux::LinuxI2CError;
+
+    fn read(&mut self, address: u8, buffer: &mut [u8]) -> Result<(), Self::Error> {
+        self.set_address(address)?;
+        self.inner.read(buffer)
+    }
+}
+
+impl hal::blocking::i2c::Write for I2cdev {
+    type Error = i2cdev::linux::LinuxI2CError;
+
+    fn write(&mut self, address: u8, bytes: &[u8]) -> Result<(), Self::Error> {
+        self.set_address(address)?;
+        self.inner.write(bytes)
+    }
+}
+
+impl hal::blocking::i2c::WriteRead for I2cdev {
+    type Error = i2cdev::linux::LinuxI2CError;
+
+    fn write_read(
+        &mut self,
+        address: u8,
+        bytes: &[u8],
+        buffer: &mut [u8],
+    ) -> Result<(), Self::Error> {
+        self.set_address(address)?;
+        self.inner.write(bytes)?;
+        self.inner.read(buffer)
+    }
+}
+
+impl ops::Deref for I2cdev {
+    type Target = i2cdev::linux::LinuxI2CDevice;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl ops::DerefMut for I2cdev {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.inner
+    }
+}
+
 /// Newtype around [`spidev::Spidev`] that implements the `embedded-hal` traits
 ///
 /// [`spidev::Spidev`]: https://docs.rs/spidev/0.3.0/spidev/struct.Spidev.html