i2c.rs

enum Address {
    U7(u8),
    U10(u16),
}

pub trait I2c {
    type Err;
    type Sess: Session<Err = Sess::Err>;

    /// "Connect" to a slave I2C device
    ///
    /// NOTE(impl) this takes care of sending START and STOP
    fn connect<F>(&mut self,
                  address: Address,
                  session: F)
                  -> Result<(), Self::Err>
        where F: FnOnce(&mut Self::Sess) -> Result<(), Self::Err>;
}

/// An I2C "session"
pub trait Session {
    type Err;

    /// Reads a single byte from the slave
    fn read(&mut self) -> Result<u8, Self::Err>;

    /// Reads `buffer.len()` bytes from the slave into `buffer`
    fn read_exact(&mut self, buffer: &mut [u8]) -> Result<(), Self::Err>;

    /// Writes/sends a single byte to the slave
    fn write(&mut self, byte: u8) -> Result<(), Self::Err>;

    /// Writes/sends `bytes` to the slave
    fn write_all(&mut self, bytes: &[u8]) -> Result<(), Self::Err>;
}

fn main() -> Result<(), _> {
    let mut i2c: impl I2c = ..;

    // Read the acceleration from an accelerometer
    let mut buffer = [0; 6];
    i2c.connect(Address::U7(ACCELEROMETER_SLAVE_ADDRESS), |sess| {
            sess.write(ACCELEROMETER_REGISTER_ADDRESS)?;
            sess.read_exact(&mut buffer)
        })?;
}