Rust Spidev

Documentation

The Rust i2cdev crate seeks to provide full access to the Linux i2cdev driver interface in Rust without the need to wrap any C code or directly make low-level system calls. The documentation for the i2cdev interace can be found at https://www.kernel.org/doc/Documentation/i2c/dev-interface and in the lm-sensors projects.

Example/API

The source includes an example of using the library to talk to a Wii Nunchuck (which has an i2c interface). Go View the Example Example.

Here's a real quick example showing the guts of how you create a device and start talking to it... This device only requires basic functions (read/write) which are done via the Read/Write traits.

extern crate i2cdev;
use i2cdev::*;
use std::thread;

const NUNCHUCK_SLAVE_ADDR: u16 = 0x52;

// real code should not use unwrap() so liberally
fn i2cfun() -> Result<(), I2CError> {
    let mut dev = try!(I2CDevice::new("/dev/i2c-1", NUNCHUCK_SLAVE_ADDR));
    self.i2cdev.write_all(&[0xF0, 0x55]).unwrap();
    self.i2cdev.write_all(&[0xFB, 0x00]).unwrap();
    thread::sleep_ms(100);
    loop {
        let mut buf: [u8: 6] = [0: 6];
        self.i2cdev.write_all(&[0x00]).unwrap();
        thread::sleep_ms(10);
        self.i2cdev.read(&mut buf).unwrap();
        println!("Reading: {:?}", buf); 
    }
}

In addition to the Read/Write traits, the following methods are available via the I2CSMBus trait:

pub trait I2CSMBus {
    fn smbus_write_quick(&self, bit: bool) -> Result<(), Error>;
    fn smbus_read_byte(&self) -> Result<u8, Error>;
    fn smbus_write_byte(&self, value: u8) -> Result<(), Error>;
    fn smbus_read_byte_data(&self, register: u8) -> Result<u8, Error>;
    fn smbus_write_byte_data(&self, register: u8, value: u8) -> Result<(), Error>;
    fn smbus_read_word_data(&self, register: u8) -> Result<u16, Error>;
    fn smbus_write_word_data(&self, register: u8, value: u16) -> Result<(), Error>;
    fn smbus_process_word(&self, register: u8, value: u16) -> Result<u16, Error>;
    fn smbus_read_block_data(&self, register: u8) -> Result<Vec<u8>, Error>;
    fn smbus_write_block_data(&self, register: u8, values: &[u8]) -> Result<(), Error>;
    fn smbus_process_block(&self, register: u8, values: &[u8]) -> Result<(), Error>;
}

Features

The following features are implemented and planned for the library:

• Implement the Read trait
• Implement the Write trait
• Implement SMBus Methods
• Add Tests/Example for SMBus Methods
• Add Support for Non-SMBus ioctl methods
• Add examples for non-smbus ioctl methods
• Unit Testing

Cross Compiling

Most likely, the machine you are running on is not your development machine (although it could be). In those cases, you will need to cross-compile. The following basic instructions should work for the raspberry pi or beaglebone black:

1. Install rust and cargo
2. Install an appropriate cross compiler. On an Ubuntu system, this can be done by doing sudo apt-get install g++-arm-linux-gnueabihf.
3. Build or install rust for your target. This is necessary in order to have libstd available for your target. For arm-linux-gnueabihf, you can find binaries at https://github.com/japaric/ruststrap. With this approach or building it yourself, you will need to copy the ${rust}/lib/rustlib/arm-unknown-linux-gnueabihf to your system rust library folder (it is namespaced by triple, so it shouldn't break anything).
4. Tell cargo how to link by adding the lines below to your ~/.cargo/config file.
5. Run your build cargo build --target=arm-unknown-linux-gnueabi.

The following snippet added to my ~/.cargo/config worked for me:

[target.arm-unknown-linux-gnueabihf]
linker = "arm-linux-gnueabihf-gcc"

License

Copyright (c) 2015, Paul Osborne ospbau@gmail.com

Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or http://www.apache.org/license/LICENSE-2.0> or the MIT license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option. This file may not be copied, modified, or distributed except according to those terms.