Add doc-example to gpio

rp2040-hal/src/gpio/mod.rs

@@ -1,6 +1,36 @@
 //! General Purpose Input and Output (GPIO)
 //!
-//! See [`pin`](self::pin) for documentation.
+//! See [`pin`](self::pin) for implementation details and in-depth documentation.
+//!
+//! ## Basic usage
+//! ```no_run
+//! use embedded_hal::digital::v2::{InputPin, OutputPin};
+//! use rp2040_hal::{clocks::init_clocks_and_plls, gpio::Pins, watchdog::Watchdog, pac, sio::Sio};
+//! let mut peripherals = pac::Peripherals::take().unwrap();
+//! let mut watchdog = Watchdog::new(peripherals.WATCHDOG);
+//! const XOSC_CRYSTAL_FREQ: u32 = 12_000_000; // Typically found in BSP crates
+//! let mut clocks = init_clocks_and_plls(XOSC_CRYSTAL_FREQ, peripherals.XOSC, peripherals.CLOCKS, peripherals.PLL_SYS, peripherals.PLL_USB, &mut peripherals.RESETS, &mut watchdog).ok().unwrap();
+//!
+//! let mut pac = pac::Peripherals::take().unwrap();
+//! let sio = Sio::new(pac.SIO);
+//! let pins = rp2040_hal::gpio::Pins::new(pac.IO_BANK0, pac.PADS_BANK0, sio.gpio_bank0, &mut pac.RESETS);
+//! // Set a pin to drive output
+//! let mut output_pin = pins.gpio25.into_push_pull_output();
+//! // Drive output to 3.3V
+//! output_pin.set_high().unwrap();
+//! // Drive output to 0V
+//! output_pin.set_low().unwrap();
+//! // Set a pin to input
+//! let input_pin = pins.gpio24.into_floating_input();
+//! // pinstate will be true if the pin is above 2V
+//! let pinstate = input_pin.is_high().unwrap();
+//! // pinstate_low will be true if the pin is below 1.15V
+//! let pinstate_low = input_pin.is_low().unwrap();
+//! // you'll want to pull-up or pull-down a switch if it's not done externally
+//! let button_pin = pins.gpio23.into_pull_down_input();
+//! let button2_pin = pins.gpio22.into_pull_up_input();
+//! ```
+//! See [examples/gpio_in_out.rs](https://github.com/rp-rs/rp-hal/tree/main/rp2040-hal/examples/gpio_in_out.rs) for a more practical example
 
 // Based heavily on and in some places copied from `atsamd-hal` gpio::v2
 pub mod pin;