BerryIMU

A pure-rust library for interfacing with BerryIMU v3.

At the moment, this is just enough functionality to support what's demoed in part 2 of the raspberry pi guide, as this is all I needed for building a robot. Specifically, this supports reading the accelerometer and magnetometer with fixed settings on linux. Pull requests to add more functionality are welcome.

Example

This will print out the tilt-compensated heading on linux:

```rust use std::error::Error; use std::f64; use std::thread; use std::time::Duration;

use berryimu;

pub fn main() -> Result<(), Box> { let mut accelerometer = berryimu::Accelerometer::newonlinux("/dev/i2c-1")?; let mut magnetometer = berryimu::Magnetometer::newonlinux("/dev/i2c-1")?;

loop {
    let (acc_x, acc_y, acc_z) = accelerometer.read()?;
    let (mag_x, mag_y, mag_z) = magnetometer.read()?;

    // Normalize accelerometer raw values.
    let acc_x_norm =
        (acc_x as f64) / ((acc_x * acc_x + acc_y * acc_y + acc_z * acc_z) as f64).sqrt();
    let acc_y_norm =
        (acc_y as f64) / ((acc_x * acc_x + acc_y * acc_y + acc_z * acc_z) as f64).sqrt();

    //Calculate pitch and roll
    let pitch = acc_x_norm.asin();
    let roll = -((acc_y_norm / pitch.cos()).asin());

    // Calculate the new tilt compensated values
    // The compass and accelerometer are oriented differently on the the BerryIMUv1, v2 and v3.
    // This needs to be taken into consideration when performing the calculations.
    // X compensation
    let mag_x_comp = (mag_x as f64) * pitch.cos() + (mag_z as f64) * pitch.sin();
    // Y compensation
    let mag_y_comp = (mag_x as f64) * roll.sin() * pitch.sin() + (mag_y as f64) * roll.cos()
        - (mag_z as f64) * roll.sin() * pitch.cos();

    // Calculate heading in degrees
    let mut heading = 180.0 * mag_y_comp.atan2(mag_x_comp) / f64::consts::PI;
    if heading < 0.0 {
        heading += 360.0;
    }

    println!("{heading:.2f}");

    // Sleep for 25ms
    thread::sleep(Duration::from_millis(25));
}

}

```