Add some missing docs

Author: robyoung

src/display/image.rs

@@ -29,6 +29,7 @@ impl GreyscaleImage {
         GreyscaleImage(*data)
     }
 
+    /// Construct a GreyscaleImage with all LEDs turned off.
     pub const fn blank() -> GreyscaleImage {
         GreyscaleImage([[0; 5]; 5])
     }

src/gpio.rs

@@ -4,7 +4,7 @@
 //! [v1.5 schematic](https://github.com/bbcmicrobit/hardware/tree/master/V1.5).
 //! Where appropriate the pins are restricted with the appropriate `MODE`
 //! from `nrf-hal`.
-#![allow(clippy::upper_case_acronyms)]
+#![allow(clippy::upper_case_acronyms, missing_docs)]
 use crate::hal::gpio::{p0, Floating, Input, Output, PushPull};
 
 /* GPIO pads */
@@ -27,6 +27,7 @@ pub type ROW1 = p0::P0_13<Output<PushPull>>;
 pub type ROW2 = p0::P0_14<Output<PushPull>>;
 pub type ROW3 = p0::P0_15<Output<PushPull>>;
 
+/// GPIO pins connected to the LED matrix
 pub struct DisplayPins {
     pub col1: COL1,
     pub col2: COL2,
@@ -42,6 +43,7 @@ pub struct DisplayPins {
     pub row3: ROW3,
 }
 
+/// Create [DisplayPins] from a [GPIO Parts](crate::hal::gpio::p0::Parts)
 #[macro_export]
 macro_rules! display_pins {
     ( $p0parts:expr ) => {{

src/lib.rs

@@ -1,4 +1,8 @@
+//! microbit contains everything required to get started with the use of Rust
+//! to create firmwares for the fabulous [BBC micro:bit](https://microbit.org)
+//! microcontroller board.
 #![no_std]
+#![deny(missing_docs)]
 #![allow(non_camel_case_types)]
 
 pub use hal::pac;
@@ -11,6 +15,7 @@ pub mod display;
 pub mod gpio;
 pub mod led;
 
+/// Create a [Uart](hal::uart::Uart] client with the default pins
 #[macro_export]
 macro_rules! serial_port {
     ( $gpio:expr, $uart:expr, $speed:expr ) => {{