added interrupt example

examples/stm32f0/src/bin/button_exti.rs

@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::exti::ExtiInput;
+use embassy_stm32::gpio::{Input, Pull};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    // Initialize and create handle for devicer peripherals
+    let p = embassy_stm32::init(Default::default());
+    // Configure the button pin and obtain handler.
+    // On the Nucleo F091RC there is a button connected to pin PC13.
+    let button = Input::new(p.PC13, Pull::Down);
+    let mut button = ExtiInput::new(button, p.EXTI13);
+
+    info!("Press the USER button...");
+    loop {
+        button.wait_for_falling_edge().await;
+        info!("Pressed!");
+        button.wait_for_rising_edge().await;
+        info!("Released!");
+    }
+}