Add README (finally)!

Author: 9names

README.md

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+# Rust Wiimote Extension-Controller (Nunchuck/classic controller) Driver
+
+This is a platform agnostic Rust driver for Wiimote Extension controllers (Nunchuk, Classic, Classic Pro, NES Classic, SNES Classic, and clones) using the [`embedded-hal`] traits.
+
+This driver allows you to read all axes and buttons for Wiimote Extension controllers
+
+## Physical protocol details
+
+Wiimote extension controllers are designed to talk to a Wiimote over an I2C interface at 3.3V.
+The official controllers are capable of operating in fast-mode (400Khz) though some clones require normal-mode (100Khz).
+The protocol is quite simple - it's not officially documented, but it has been reverse-engineered.
+
+- http://wiibrew.org/wiki/Wiimote/Extension_Controllers
+- http://wiibrew.org/wiki/Wiimote/Extension_Controllers/Nunchuck
+- http://wiibrew.org/wiki/Wiimote/Extension_Controllers/Classic_Controller
+
+High Resolution mode is a recent addition and was only discovered once the NES Classic console was released. It is described here:
+- https://www.raphnet-tech.com/support/classic_controller_high_res/
+
+
+Wii Motion Plus support is planned, both in standalone and combo mode
+
+## Usage
+
+To use this driver, import this crate and an `embedded_hal` implementation,
+then instantiate the appropriate device.
+
+```rust
+use wii_ext::classic::Classic;
+use ::I2C; // insert an include for your HAL i2c peripheral name here
+
+fn main() {
+    let i2c = I2C::new(); // insert your HAL i2c init here
+    let mut delay = cortex_m::delay::Delay::new(); // some delay source as well
+    // Create, initialise and calibrate the controller
+    let mut controller = Classic::new(i2c, &mut delay).unwrap();
+    // Enable hi-resolution mode. This also updates calibration
+    controller.enable_hires(&mut delay).unwrap();
+    loop {
+        let input = controller.read_blocking(&mut delay).unwrap();
+        // You can read individual buttons...
+        let a = input.button_a;
+        let b = input.button_b;
+        // or joystick axes
+        let x = input.joysick_left_x;
+        let y = input.joysick_left_y;
+        // the data structs optionally implement defmt::debug
+        info!("{:?}", read);
+        // Calibration can be manually performed via
+        controller.update_calibration();
+    }
+}
+```
+
+## Status
+
+- Nunchuk is functional, no calibration yet
+- Classic controllers supported in regular and HD mode
+
+## Support
+
+For questions, issues, feature requests like compatibility with other Wiimote extension controllers please file an
+[issue in the github project](https://github.com/9names/wii-ext-rs/issues).
+
+## License
+
+Nunchuk portions of this crate are largely derived from  
+https://github.com/rust-embedded/rust-i2cdev/blob/master/examples/nunchuck.rs  
+Copyright 2015, Paul Osborne <[email protected]>
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+   http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contributing
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+
+[`embedded-hal`]: https://github.com/rust-embedded/embedded-hal