comprehensive-rust/src/exercises/bare-metal/compass.md

# Compass

We will read the direction from an I2C compass, and log the readings to a serial port. If you have
time, try displaying it on the LEDs somehow too, or use the buttons somehow.

Hints:

- Check the documentation for the [`lsm303agr`](https://docs.rs/lsm303agr/latest/lsm303agr/) and
  [`microbit-v2`](https://docs.rs/microbit-v2/latest/microbit/) crates, as well as the
  [micro:bit hardware](https://tech.microbit.org/hardware/).
- The LSM303AGR Inertial Measurement Unit is connected to the internal I2C bus.
- TWI is another name for I2C, so the I2C master peripheral is called TWIM.
- The LSM303AGR driver needs something implementing the `embedded_hal::blocking::i2c::WriteRead`
  trait. The
  [`microbit::hal::Twim`](https://docs.rs/microbit-v2/latest/microbit/hal/struct.Twim.html) struct
  implements this.
- You have a [`microbit::Board`](https://docs.rs/microbit-v2/latest/microbit/struct.Board.html)
  struct with fields for the various pins and peripherals.
- You can also look at the
  [nRF52833 datasheet](https://infocenter.nordicsemi.com/pdf/nRF52833_PS_v1.5.pdf) if you want, but
  it shouldn't be necessary for this exercise.

Download the [exercise template](../../comprehensive-rust-exercises.zip) and look in the `compass`
directory for the following files.

`src/main.rs`:

<!-- File src/main.rs -->

```rust,compile_fail
{{#include compass/src/main.rs:top}}
use microbit::{hal::uarte::{Baudrate, Parity, Uarte}, Board};

{{#include compass/src/main.rs:main}}
    // TODO

{{#include compass/src/main.rs:loop}}
        // TODO
    }
}
```

`Cargo.toml` (you shouldn't need to change this):

<!-- File Cargo.toml -->

```toml
{{#include compass/Cargo.toml}}
```

`Embed.toml` (you shouldn't need to change this):

<!-- File Embed.toml -->

```toml
{{#include compass/Embed.toml}}
```

`.cargo/config.toml` (you shouldn't need to change this):

<!-- File .cargo/config.toml -->

```toml
{{#include compass/.cargo/config.toml}}
```

See the serial output on Linux with:

```sh
picocom --baud 115200 --imap lfcrlf /dev/ttyACM0
```

Or on Mac OS something like (the device name may be slightly different):

```sh
picocom --baud 115200 --imap lfcrlf /dev/tty.usbmodem14502
```

Use Ctrl+A Ctrl+Q to quit picocom.