Add gpio erased example

Author: Sh3Rm4n

Cargo.toml

@@ -139,3 +139,7 @@ required-features = ["stm32f303"]
 [[example]]
 name = "i2c_scanner"
 required-features = ["stm32f303xc"]
+
+[[example]]
+name = "gpio_erased"
+required-features = ["rt", "stm32f303xc"]

examples/gpio_erased.rs

@@ -0,0 +1,56 @@
+// TOOD Implement:
+// https://github.com/dfrankland/proton-c/commit/0289f1cfa15000d6b1b2a8175420c16ffdff7451
+#![no_main]
+#![no_std]
+
+use panic_semihosting as _;
+
+use cortex_m::asm;
+use cortex_m_rt::entry;
+use cortex_m_semihosting::hprintln;
+
+use hal::gpio::{self, Floating, Input};
+use hal::pac;
+use hal::prelude::*;
+use stm32f3xx_hal as hal;
+
+#[entry]
+fn main() -> ! {
+    let dp = pac::Peripherals::take().unwrap();
+
+    let mut rcc = dp.RCC.constrain();
+    let mut gpiob = dp.GPIOB.split(&mut rcc.ahb);
+    let mut gpioc = dp.GPIOC.split(&mut rcc.ahb);
+    let mut gpiod = dp.GPIOD.split(&mut rcc.ahb);
+
+    let mut pin_array: [gpio::PXx<Input<Floating>>; 4] = [
+        gpiob
+            .pb11
+            .into_floating_input(&mut gpiob.moder, &mut gpiob.pupdr)
+            .downgrade()
+            .downgrade(),
+        gpioc
+            .pc4
+            .into_floating_input(&mut gpioc.moder, &mut gpioc.pupdr)
+            .downgrade()
+            .downgrade(),
+        gpiod
+            .pd3
+            .into_floating_input(&mut gpiod.moder, &mut gpiod.pupdr)
+            .downgrade()
+            .downgrade(),
+        gpiod
+            .pd2
+            .into_floating_input(&mut gpiod.moder, &mut gpiod.pupdr)
+            .downgrade()
+            .downgrade(),
+    ];
+
+    hprintln!("Start scanning pin array").unwrap();
+    loop {
+        for pin in pin_array.iter_mut() {
+            hprintln!("Value is {}", pin.is_high().unwrap()).unwrap();
+            asm::delay(1_000);
+        }
+    }
+}

src/gpio.rs

@@ -156,6 +156,14 @@ macro_rules! gpio {
         }
 
         /// Fully erased pin
+        ///
+        /// This moves the pin type information to be known
+        /// at runtime, and erases the specific compile time type of the GPIO.
+        /// It does only matter, that it is a GPIO pin with a specific MODE.
+        ///
+        /// See [examples/gpio_erased.rs] as an example.
+        ///
+        /// [examples/gpio_erased.rs]: https://github.com/stm32-rs/stm32f3xx-hal/blob/v0.5.0/examples/gpio_erased.rs
         pub struct PXx<MODE> {
             i: u8,
             gpio: Gpio,